A Visual Analysis and Review of Chinese Qilou Architectural Heritage Based on CiteSpace

Abstract

Chinese Qilou Architecture Heritage (CQAH) serves commercial and residential functions, integrates Southeast Asian and local Chinese architectural features, and is a unique testimony to modern commerce and culture of the overseas Chinese hometown. Since the 1990s, the academic community has conducted extensive research on CQAH. This paper utilizes CiteSpace 6.4.R1 as the research tool and China National Knowledge Infrastructure (CNKI) as the core database, with “Qilou” as the core keyword and “Chinese Qilou Architecture” and “Qilou District” as the research themes. After a rigorous data collection procedure, 491 documents were obtained and subjected to visual analysis. The results show that research on CQAH is most prevalent in the field of architectural science and engineering, primarily focusing on four key issues: the distribution area and historical origin of Qilou, differences in regional characteristics of Qilou architecture, conservation and renewal of the Qilou historic district in urban development, and cultural inheritance and spatial activation. The research can be divided into four stages: exploration of basic features and historical background, exploration of architectural origins and development motives, cultural heritage protection and adaptive use, diversified perspectives, and multidisciplinary integration. Correspondingly, this paper also proposes four priority research directions for the future. This study provides theoretical support and practical reference for the conservation of CQAH and offers new methods and perspectives for the study of the future sustainable development of Qilou.

1. Introduction

Chinese Qilou Architecture (abbreviated as CQA), as a functional mixed-use building, combines two functions: retail and residential. Compared to other mixed-use buildings, CQA consists of a gallery on the ground floor and Shophouses along the street. Qilou is a composite architectural form that combines architecture with urban streets, possessing both architectural and urban characteristics [1] (Figure 1). CQA is a distinct type of overseas Chinese hometown architecture (overseas Chinese hometowns mainly refer to places in China where many overseas Chinese and their families are concentrated and are generally not divided by provincial regions) based on the fusion of Southeast Asian exterior corridor-style architectural forms and local cultural characteristics and is a critical component of China’s township development process [2,3]. The promulgation of cultural heritage protection policies, including the Regulations on the Protection of Famous Historical and Cultural Cities, Towns and Villages [4], Urban and Rural Planning Law of the People’s Republic of China [5], The Regulation on the Protection of the Qilou Buildings on Zhongshan Road in Quanzhou City [6], and Regulations on the Protection of Wuzhou Qilou Cultural Block in Guangxi Zhuang Autonomous Region [7] has elevated public awareness of Qilou architecture while establishing a legal framework for its preservation and sustainable utilization. Qilou not only serves as an essential carrier of China’s regional architectural cultural heritage but also warrants further exploration of its architectural form, spatial layout, and decorative features. Additionally, it has become a valuable medium for studying the history of cultural exchanges between China and other countries.

Qilou represents a highly developed and unique architectural form in China, particularly within the Lingnan region. However, the nomenclature and provenance of this form have been the subject of debate, primarily due to the intricacies of its formation process and the influence of numerous elements. Qilou exhibits distinct characteristics in different regions, resulting in a variety of names assigned to the riding structures. In Southern Fujian, Qilou is called “gɔ^6-5-kha^1-6-ki⁵” (“gɔ^6-5-kha^1-6-ki⁵” is a term in the Southern Fujian dialect. The transliteration is from the “Southern Fujian Dialect Dictionary”, which records the pronunciation of local dialects in Southern Fujian [8]). In Taiwan, Qilou is called “the foot of the pavilion” (Taiwanese). Due to Taiwan’s rainy and humid climate, Qilou is commonly built in various cities and towns. “The foot of the pavilion” means a building constructed on the roadside for people to rest, shelter from rain, or enjoy the cool breeze. This type of building has no walls but only a roof [3]. In English, the term “Qilou” is alternatively known as “Qilou”, “arcade-house”, and “sotto portico”. In English literature, “Qilou” is more widely used [9,10,11]. A school of thought among scholars favors the designation “arcade-house” and posits that Qilou is a type of arcade building [12]. The official appellation “Qilou” emerged in 1912 with the promulgation of the “Regulations on the Prohibition of Buildings and Implementing Rules” by the Republic of China government. This legislative act designated this architectural typology as “Qilou with feet”. Later, in the Revision of the Regulations on the Prohibition of Buildings, it was simplified to “Qilou”, and then in the Pearl River Delta region, this type of building was called “Qilou” [1] (Figure 2).

There are a variety of academic views and interpretations of the definition of Qilou. Ci Hai (Ci Hai is one of the authoritative reference books in China, which is a large-scale comprehensive dictionary that includes both language and encyclopedia entries) defines Qilou as “the part of a building that extends outward and covers the sidewalk; the sidewalk under the building is called the bottom of the building”. Xie Xuan and Luo Jianyun define Qilou as “a covered passageway, especially a building with arcades with stores on one or both sides”, which they consider to be an open-aisle commercial building [13]. Professor Peng Changxin and other scholars posit that Qilou originated in the late Qing Dynasty, the prototype of which is the “paved corridor” (In 1889, Zhang Zhidong, the Governor-General of Huguang, proposed two measures for embankment construction: “paved corridor” and “stack construction.” Among these, the “paved corridor” closely resembles the structure of Qilou buildings) [14]. This was an imported product that gradually transitioned from the existence of the urban system to the type of architecture, and became a model of the urban street house [15]. Julian Davison’s definition of a Qilou from a functional level stipulates that a Qilou is a building with a store on the first floor and a residence on the second floor, with two to three floors built for merchants and their families [16]. Professor Chen Zhihong reinterpreted Qilou from the formal level, stating that Qilou is a special way of combining buildings along the street to limit the street and organize the walking [17]. A comprehensive and widely accepted conceptual definition of Qilou remains elusive within the academic milieu. However, the corridor style of architecture and the integration of commercial and residential functions are recognized as spatial characteristics that are distinctive to Qilou.

Although Qilou has been around since the 1930s, there is still a lack of comprehensive historical records, particularly in the early history of Qilou in the Lingnan region, where early records are few and fragmentary. The research on Qilou in China National Knowledge Infrastructure dates back to 1980, in which Qi Kang points out that the Qilou architecture of Chester is significantly different from the Chinese Qilou in terms of function and form. The study promotes the cultural heritage and practical exploration in the field of urban planning in China [18]. After the 1990s, scholars gradually began to pay attention to the architectural style, commercial function, and regional culture of Qilou, as well as the preservation and development of Qilou in urban renewal [19,20,21,22,23]. At the beginning of the 21st century, the study of CQA underwent a significant expansion in terms of multidisciplinary integration, precipitated by the advancement of research techniques and the gradual intermingling of disciplines. The development of CQAH has been explored and discussed in geographical distribution and landscape diversity [1,24,25,26,27], origins and motives for development [24,25,28,29], architectural scale and characteristics of equestrian buildings [13], heritage conservation [30,31,32,33], and future sustainable development model [32,33].

From the perspective of Qilou’s academic research, the study of CQA and Qilou Street focuses more on individual cases or a particular district. For instance, Lin Lin examines the Qilou in Guangdong, investigating its historical origins within the context of Qilou architecture. Xie Xuan and Luo Jianyun provide a comprehensive overview of the development period of Qilou, extending their analysis to explore the spatial dimensions of Qilou architecture in Beihai City, Guangxi Province. Professor Chen Zhihong, in turn, delves into the distinctive characteristics of the Qilou architecture in the Southern Fujian region. A paucity of systematic comparative studies on Chinese Qilou exists in the Web of Science (abbreviated as WOS) or the China National Knowledge Infrastructure (abbreviated as CNKI), even though certain scholars have explored the origin and evolution of Qilou. Whether there are commonalities or individualities in the evolution of Qilou in different regions remains unanswered. The prevailing Qilou model continues to be a combination of traditional commercial and residential development, which is not a sustainable approach to safeguarding this valuable architectural heritage in the new era.

From the perspective of Qilou’s developmental practice, this distinctive typology primarily functions as an urban institution intrinsically linked to planning strategies and regulatory frameworks, with its architectural spatial entity being a secondary manifestation [3,34]. Academician Chang Qing and Professor Fang Yong are leading scholars in this research field. The construction of Qilou evolved alongside urban planning and old-city renovation, transitioning from informal folk practices to government-backed initiatives. Initially imitative, it later achieved a harmonious integration with regional architecture. This process reflects the blending of Chinese and foreign cultures, demonstrating a gradual acceptance of foreign influences in local architectural traditions. At the beginning of the twentieth century, many cities had already implemented Qilou construction. However, with the rapid development of urbanization, Qilou architecture and the historic districts in which it is located are facing problems: Qilou Street is mostly a monolithic, mechanical urban form, lacking regional characteristics in the design of the architectural style of Qilou architecture, as well as the excessive pursuit of economic benefits. Qilou Street has pursued economic benefits, and the activity area has been encroached upon.

This study employs CiteSpace 6.4.R1 as the research tool to conduct a visual analysis and review of research on Chinese Qilou Architectural Heritage. It aims to accurately and intuitively examine the literature’s distribution characteristics, collaborative characteristics, key issues, research trends, and hot spots of the relevant studies. Additionally, it offers suggestions for the future research directions of Qilou architectural heritage and provides a guidance manual for the protection and sustainable development of CQAH.

2. Materials and Methods

2.1. Study Area and Research Questions

It can be seen that the development of research on CQAH is shifting towards the diversification of research perspectives, the complexity of research problems, and the integration of multiple disciplines. Consequently, a bibliometric analysis that visualizes and combines multiple perspectives on the extant research results of CQAH is a task of paramount importance. Based on the above analysis, this study focuses on exploring the following three key research questions (RQs) through visual analysis and review of existing research on CQAH (Figure 3).

RQ1. What are the characteristics of CQAH’s literature distribution, and how do influential authors and institutions collaborate?

RQ2. What are the key issues, research trends, and research hotspots of CQAH?

RQ3. What are the future exploration directions of CQAH?

The remainder of the paper builds on the three key research questions. Section 2 deals with the collection of statistical data and the methodology of data analysis for the CQAH study. This includes the selection of analytical tools and a description of the data collection process. Section 3 is the visualization and analysis of the collected data. The annual publication trends, disciplines of literature sources, and publications of literature sources of CQAH were collected to further analyze the characteristics of literature distribution. Impact factors were calculated based on the existing research in the field and the researchers. This paper examines the collaborative characteristics of high-impact co-authors and collaborating institutions, and then describes and analyzes their collaborative relationships. It summarizes their research content, which in turn answers RQ1. By analyzing keyword co-occurrence and clustering, this paper generalizes and summarizes the key issues in the CQAH research process. By dividing the research stages through the analysis of keyword timeline mapping and burst keyword analysis, this paper concludes the research hotspots of the study, which in turn answers RQ2. Section 4 focuses on the future research directions explored by CQAH and proposes better research suggestions for the development of this research field, which in turn answers RQ3. Section 5 is the conclusion of the article.

Through the systematic and in-depth visualization and analysis of CQAH research, this paper can more clearly identify its significance in various aspects such as culture, history, and society. Therefore, this study helps to fill the gap in the visualization and analysis of CQAH research. It also serves as a reference for future priority research directions and provides guidance for the conservation and sustainable development of CQAH.

2.2. Selection of Analysis Tool

Developed by Professor Meichao Chen at Drexel University, the CiteSpace 6.4.R1 is a document analysis visualization tool. Its core functionality relies on multiple algorithms. These include the LLR algorithm, the MI algorithm, and the critical path algorithm. The combination of these algorithms enables the software to efficiently process literature data and assist researchers in identifying hotspots, frontiers, and knowledge evolution. The software facilitates the visualization of the hidden knowledge network structure between literature and enables the comprehensive presentation of research trends, research contents, and collaborative relationships between authors and research institutions in the field of scientific and technological knowledge. The construction of a knowledge graph enables the analysis of research hotspots over time by examining the year keywords first appeared, as well as the analysis of research trends and content. This software facilitates the tracking of research hotspots, disciplinary frontiers, and emerging research directions in the research field [35]. In the contemporary era, the utilization of CiteSpace 6.4.R1 has become pervasive within the domains of scientific research, academic assessment, and intelligence analysis.

The key feature of the CiteSpace 6.4.R1 is the ability to create multiple bibliometric networks. It can be used to visualize and objectively display collaborative feature analysis, keyword co-occurrence analysis, keyword clustering analysis, and timeline mapping using a variety of analytical methods [36,37]. CiteSpace’s ability to recognize Chinese characters is superior to other bibliometric analysis applications. This advantage allows it to process and analyze literature more accurately -and efficiently, significantly improving the reliability and validity of Chinese literature analysis. The software can dig deeper into the potential information in Chinese literature, providing researchers with more comprehensive data support and helping them to make more accurate research and decisions in related fields [38].

Overall, the CiteSpace 6.4.R1, with its unique calculation mechanism and intuitive visualization and analysis functions, provides strong support for solving the research questions in this thesis. Its collaborative characteristics analysis can effectively answer RQ1. Through keyword co-occurrence analysis, cluster analysis, time mapping, and keyword burst analysis, the research questions can be clearly answered for RQ2. On this basis, it further proposes suggestions for the future development of the districts, solving RQ3. Therefore, this paper adopts CiteSpace version 6.4.1 to conduct bibliometric analyses of the relevant CQAH literature, which was econometrically analyzed.

2.3. Keyword Selection and Data Collection Procedure

2.3.1. Keyword Selection Criteria

The selection of keywords needs to meet two key points. Firstly, based on the definition of the research object, the bottom layer of the research object is supported by columns, forming a continuous public space for pedestrian traffic. Therefore, both corridor-style and open corridor-style buildings conform to this characteristic, including but not limited to Qilou buildings. Secondly, based on the functional types of the research object, it can be roughly divided into three categories: the combination of commercial and residential, purely residential, and the combination of residential and public functions.

After analyzing the research findings in this field, this paper tends to suggest that Qilou is not restricted by its functional form. In other words, it can serve any of the functions mentioned in the second key point above. In terms of spatial form, it should comply with the first key point by forming a continuous space that allows pedestrians to pass through. Secondly, the subject of study must also be an integral part of the urban system and road planning. Studies have shown that the promotion and construction of Qilou are closely related to the urban system. For example, in 1918, at the beginning of the demolition and road construction in Guangzhou, Guangdong Province, China, the municipal authorities relaxed restrictions on the construction of Qilou, allowing property owners to build Qilou above sidewalks. The municipal authorities used this measure to compensate for the land area relinquished due to road development, and the concept of “Qilou Land” was thus born [35]. This unique spatial form is an essential component of urban road planning.

Qilou architecture emphasizes the interconnection between architectural design and urban planning. Characterized by columns that define its facade and a structure composed of interconnected units, Qilou creates a continuous public space that resembles a street, commonly referred to as a Qilou street. Considering these distinctive features, this paper identifies “Qilou” as the core keyword and focuses on “Chinese Qilou Architecture” and “Qilou Street” as the primary themes. This approach excludes broader categories such as corridor-style and open corridor-style buildings, allowing for a more precise and targeted study.

2.3.2. Data Collection Procedure

We conducted a preliminary search of the literature containing the word “Qilou” in the title through internationally recognized databases, including Web of Science (Core Collection), Google Scholar, ScienceDirect, Wiley Online Library, CNKI, and Springer Link. We found that most of the research on this topic has so far been concentrated in CNKI, with no more than 30 studies in Web of Science (Core Collection), Google Scholar, ScienceDirect, Wiley Online Library, and Springer Link databases (searched on 16 February 2025). CNKI contains more than 2 million Chinese academic resources and is one of the most authoritative academic resource platforms in China. Its academic authority is reflected in its extensive resource coverage, authoritative data sources, rigorous peer review, government and Ministry of Education endorsement, data accuracy, comprehensive subject coverage, full-text access services, and academic communication platforms, making it an important literature retrieval and communication tool for Chinese scholars [39,40,41]. Therefore, we found CNKI to be reliable as the database of choice for this paper.

Since Chinese Qilou is called differently in Chinese, we chose the theme “Qilou architecture” or theme “Qilou Street” as the search route, and the title “Qilou” as further and more precise screening, with an unlimited timeframe of 16 February 2025 for the search. We initially obtained a total of 616 documents, including 404 journal articles and 88 dissertations.

After the initial search, we adopted the following detailed inclusion and exclusion criteria to ensure the accuracy and reliability of the study: topical relevance, type of literature, data integrity, and publication date. Documents with low relevance, non-academic nature, duplication, and incomplete data will not be included in the scope of this study. Using the specified topics and keywords as search parameters, we began to exclude the following categories of papers that have low relevance to this study:

• The keywords include terms similar to “Qilou” or “corridor-style”, yet the research subject and content have no connection to Qilou.
• The title contains words like “Qilou”, but the research subject and content lack a strong correlation with Qilou architecture or Qilou historic districts.
• Both the keywords and the title incorporate Qilou-related terms, but the research content pertains to other disciplines and exhibits minimal overlap with this field.
• Exclude irrelevant articles, such as newspaper reports and books, as these typically do not undergo rigorous peer review and tend to have low academic value and reliability. This step ensures that the literature selected holds reference and analytical value.

Based on the above standards, we repeatedly checked the content and basic data of each study to ensure that it contained information such as author, institution, keywords, abstract, publication date, etc., and obtained 491 valid sample literature. The data export and analysis were the final steps in the research process. It was determined that the Refworks format would be used as the primary data source, and the data was analyzed further using CiteSpace 6.4.R1 after the initial format conversion.

Prior to the analysis of the data using CiteSpace 6.4.R1, it is necessary to adjust the software’s parameters. The time slice should be set to 1 year, with the starting year unrestricted and the ending year set to 2025. The source of clustering terms should be set to default. Prior to running the CiteSpace 6.4.R1, the parameters were set as follows: (1) the time span was set as 1994–2024 (the type of filtered literature was journals and dissertations, and the earliest year we retrieved was 1994); (2) the year per slice was set as 1; (3) the node type was set as author/institution/thesis. We used CiteSpace 6.4.R1 to conduct collaborative characteristics analysis and keyword analysis on the articles we screened.

3. Results

3.1. The Literature Distribution Characteristics

3.1.1. The Trend of Annual Publications

The number of papers published can indicate the accumulation of knowledge and depth of research in a specific field [42,43], based on the data statistics and econometric analyses of the literature we screened (Figure 4). CQAH research is divided into four distinct stages, each with its own set of patterns in the field’s development. The initial stage, which lasted from 1994 to 2000, was distinguished by a low publication rate of 1–6 articles per year, indicating that the research landscape was stable. This stage also saw the first minor surge in research activity in 1996. The subsequent phase, which lasted from 2001 to 2007, saw a steady rise in the number of articles, as well as a gradual increase in scholarly interest in Qilou’s research. The third phase, from 2008 to 2017, saw a steady increase in the number of articles published. The number of articles increased from 16 in 2008 to a high of 41 in 2017, representing the most significant period of growth in research enthusiasm. The final phase, which runs from 2018 to 2024, shows a consistent level of activity, indicating that there is still a strong interest in this field of research. In this study, the inconsistency in the time span indicates that research development in this field is uneven. These fluctuations are related to the implementation of cultural heritage protection policies, the need for Qilou protection in the process of urbanization, and the academic community’s emphasis on traditional cultural heritage.

3.1.2. Source Disciplines of the Literature

As illustrated in Figure 5, the metrological study of the disciplines comprising the literature source revealed that the Peking University Core, Chinese Social Science Citation Index, Chinese Science Citation Database, Chinese Medical Journal Evaluation Standard, and World Journal Impact Index are among the major Chinese academic publications from which 15% of the literature was derived. These journals are considered to be of significant scholarly importance for the study of Qilou. The analysis further delineates the disciplines of architectural science and engineering (46%), tourism (8.04%), culture (3.55%), geography (3.55%), archaeology (1.68%), secondary education (1.50%), and fine arts and photography (1.50%) as the primary focus of the majority of studies on Qilou (Figure 5).

The data indicate that building science and engineering significantly lead research in this field, highlighting substantial scholarly interest in traditional architectural aspects such as structure, design, and materials. Although geographical and climatic factors are pertinent to Qilou ventilation and shading, they have garnered limited academic attention [10,44]. Additionally, other specific areas related to Qilou, including archival preservation, descriptive documentation, and artistic expression, remain underexplored and lack systematic research. This research concentration may overshadow the multifaceted nature of Qilou, neglecting its social functions, economic value, and community impact. Therefore, conducting multidimensional research and exploration of Qilou is imperative.

3.1.3. Source Publications of the Literature

The Huazhong Architecture publication, comprising 16 articles, is the most prominent in the field, signifying the journal’s extensive research on CQAH. The publication’s content is centered on the historical evolution of Qilou, their architectural styles, and their role in urban development [45,46,47].

Among the CQAH-related papers published in this journal, Lin Chong’s “The Initial Study on the Developmental Reason of Guangdong Modern Arcade Building”, published in 2001, has received much attention. He concludes that the development of modern Qilou in Guangdong has been driven by both the urban renewal movement and the overseas Chinese background [48]. In 2005, Lin Chong continued to publish his paper “Textual Research on the Development of Modern Arcade in Guangzhou” in the same journal. He divided the development of Qilou in Guangzhou into four periods: the initial regulations and municipal construction (1911–1917), the period of development during the Municipal Office period (1918–1920), the comprehensive development and construction during the Municipal Office period (1921–1929), and the period of decline in the development of Qilou (1930–1937). His research has spurred other scholars to study Qilou in Guangdong, directing scholars’ attention to the link between Qilou and urban planning [24]. In 2006, Chen Zhihong published his paper “Research of Modern Qilou in the South of Fujian” in the same journal. Based on his previous research on Xiamen Qilou architecture, he focuses on Qilou architecture in southern Fujian, exploring the construction process of Qilou, focusing on the monolithic and street level of the building, and comparing Qilou architecture in southern Fujian with the traditional wooden Qilou in mountainous areas [29]. It provides a reference for the subsequent research on Qilou in southern Fujian, as well as the exploration of the interaction between Qilou and urban space.

The second is Urbanism and Architecture with 15 documents, indicating that this journal has also contributed to CQAH, with research focusing on the historical and cultural values of Qilou and its conservation strategies [49,50,51,52]. Among the papers on CQAH published in Urbanism and Architecture, there is the 2020 paper by Dai Zhijian, “Research on the Urban Regeneration of Yongchun Wuli Arcade Historic Street from the Perspective of Value Analysis”, a study that focuses on people’s perceptions of historic neighborhoods during the preservation process. He pays attention to the current situation of this Qilou historical district, and based on the value orientation, the scholar proposes to protect three renewal strategies, including the restoration of the overall style, the improvement of the human environment, and the adjustment of the economic structure. His study points out that the root cause of the development problems of Wuli Street is due to people’s unclear perception of the value of the historic district [53]. In 2021, Zhang Le Min’s team published “Study on the Style Perception of the Commercial Historical Street Based on Eye-Tracking--A Case of Arcade Street in Shapowei, Xiamen”, which combines new technologies with the preservation of historic district. With the help of eye-tracking equipment, this study explores the environmental requirements that have a greater impact on human perception in Xiamen Shabowei Qilou, with a view to advancing the design and management of urban landscapes and providing a reference for landscape control in the renewal of historic neighborhoods [54].

Furthermore, Chinese and Overseas Architecture, South Architecture, and Huaqiao University publications each contain twelve articles, with a focus on the regionalized types and architectural characteristics of riding buildings [2,19,55,56,57,58,59,60]. Furthermore, several academic journals, including Architecture & Culture, the Journal of Hainan Normal University, and the South China University of Technology, have also made significant contributions to CQAH research (Figure 6).

The study of CQAH has established a relatively systematic academic framework, covering multiple dimensions such as history, culture, and technology. However, there is still room for improvement in both the depth and breadth of research. For instance, comparative studies across regions are relatively scarce, and there is a lack of unified theoretical support for the conservation and renewal strategies of Qilou in different areas. Moreover, while the introduction of new technologies has brought new research methods, further exploration is needed on how to better apply these technologies to actual conservation work.

3.2. Analysis of Collaborative Characteristics

Collaborative characteristics are a term used to describe the key attributes or behavioral patterns that are manifested during the collaborative process. These attributes include, but are not limited to, behaviors such as information sharing, common goals, interactive communication, trust, and cooperation. The practice of collaborative characteristics has the capacity to reveal influential authors and institutions in a given field. Furthermore, it can demonstrate collaborative relationships between different fields and scholars [39,41]. This paper demonstrates the level of collaboration at different levels of existing research on CQAH and analyzes the direction of collaboration in depth through co-authors and partner organizations.

3.2.1. Collaborating Authors

We import the selected literature into CiteSpace 6.4.R1 and select the collaborating authors’ analyses. Given the abundance of author networks, the ‘largest connected components to show’ parameter is set to 50, thereby displaying the 50 largest author networks in the collaborating author’s analysis graph. The focus is then directed towards the core collaborative networks, with the authors who have relatively close relationships being filtered out. This process results in the simplification of the complex network structure, and the conducting of targeted analysis. The outcome of this process is the creation of a collaborative author network graph for Qilou’s research area (Figure 7). Each node in the graph represents an author, and the size of the node is usually related to the author’s influence in the field or the number of papers published. The presence of connecting lines between the nodes is indicative of cooperation between the authors, with the frequency and proximity of this cooperation being implied by the thickness of the lines.

Furthermore, 23 authors have been identified who have made three or more research contributions, and a tabular representation of these authors and their respective publications has been compiled (

Table 1. The most productive authors in the field of CQAH (top 23, including parallel rankings).

Rank	Author	Frequency *	Year
1	Yang Honglie	10	1998
1	Gan Guanlan	10	2012
3	Yu Yang	7	2014
3	Jiang Li	7	2014
5	Wang Shan	6	2003
5	Mo Xianfa	6	2012
7	Zhou Yixin	5	2006
7	Xie Hao	5	2003
7	Liu Xiaofan	5	2003
7	Lin Lin	5	2001
11	Chen Jing	4	2008
11	Yang Sisheng	4	2005
11	Zhu Chaoping	4	2012
23	Jie Zhang	3	2022
23	Wang Fang	3	2011
23	Chen Zhihong	3	2006
23	Lin Chong	3	2001
23	Wang Mo	3	2015
23	Liu Jiaping	3	2011
23	Duan Xianggui	3	2013
23	Zhang Ying	3	2015
23	Guan Ruiming	3	2002
23	Li Jinlin	3	2016

* Frequency reflects the number of co-authored publications by two or more authors, which can be used to measure the degree of cooperation between authors, and there is a positive correlation between the two.

).

In light of the data presented in the preceding tables and images, and in conjunction with the research on CQAH, a categorization of research on CQAH into academic research and practical research has been undertaken, according to research perspectives. In the domain of academic research, the studies of academicians such as Chen Zhihong, Lin Chong, and Lin Lin have exerted a profound influence on the field. In the domain of practical research, the contributions of academicians Chang Qing, Fang Yong, and Zhang Jie have been particularly influential.

Chen Zhihong initiated his research on contemporary architectural buildings in Southern Fujian in the 90s, undertaking a comparative study of Qilou from street and monolithic perspectives. He posits that the construction of Qilou embodies a cohesive urban planning approach for the renovation and reconstruction of traditional shophouses within the context of City Renewal. He has further explored the contemporary value of Qilou, emphasizing that the evolution of Qilou architecture should transcend the conventional model by incorporating diverse experiences to establish a novel design methodology and theoretical framework [1,16,17]. In 2006, Lin Lin provided a comprehensive discussion on the historical origins of Guangdong Qilou, proposing that this distinctive architectural style is the result of a complex interplay between multiple cultural influences. The evolution of Qilou is intricately intertwined with the dynamics of trade and commerce, the necessity of adapting to local climatic conditions, and the influence of colonial cultural elements. By integrating the disciplines of human geography and architecture, Lin Lin offers a novel approach that combines spatial evolution and social network analysis to elucidate the multifaceted function of Qilou as an “urban interface” [1]. Lin Chong began to explore the development of Qilou in Guangdong in 2001, and he proposed that Qilou is the result of cultural collision and pragmatic rationality in the process of urbanization in modern Guangdong, and its morphological evolution reflects the dynamic adaptation of colonial modernity and local tradition [24,34].

Academician Chang Qing is a renowned figure in the domain of vernacular architecture within China. He possesses a wealth of knowledge in theoretical research and actively contributes to practical conservation endeavors in Qilou. In the direction of academic research, in the early 1990s, academician Chang Qing mainly focused on local Qilou. He led a team to map and sustainably conserve the Qilou historic district in Haikou and researched the historical evolution and characteristics of Qilou in Haikou, as well as the role of Qilou in the city. In addition, in 2010, he also participated in the actual project of Qilou preservation and renewal to promote the sustainable development of CQAH conservation. In 2018, he advocated a philosophy of “Coexistence of the old and the new, harmony in diversity”, underlining the necessity of innovation in preserving the historic character of Qilou [3,61]. Fang Yong’s research on Qilou has been widely recognized for its pioneering contributions to architectural research. In the 1990s, Fang not only conducted in-depth research on Qilou architecture, historical background, and cultural value but also began to participate in the Quanzhou Qilou planning and protection program in 1996. He conducted a systematic investigation and research on Qilou on Zhongshan Road in Quanzhou, which filled the blank of the systematic research on Qilou in Quanzhou. In 1997, Fang published “Investigation and Conservation Planning of Zhongshan Road and Qilou Buildings in Licheng, Quanzhou”, which shows that his research on Qilou architecture is not only limited to the static thinking of traditional architecture conservation. Fang Yong’s approach integrates physical restoration, functional revitalization, and cultural preservation, establishing a framework for the sustainable renewal of historic districts in contemporary China [20,62]. In 2022 and 2023, Jie Zhang’s team explored in detail the historical and cultural values, current status, and conservation and regeneration projects of the Lixin Qianjin neighborhood in Nan’an City, Quanzhou, Fujian Province, and the Qilou historic district in Haikou, Hainan Province, respectively [63,64,65].

A review of the extant literature reveals the existence of aggregated networks of teamwork in the domain of CQAH-related research. While there are also collaborations between scholars in universities, the majority of researchers tend to work as individuals or in small groups. The multiple small groups distributed in the figure indicate the existence of diverse research teams and research directions within the field of Qilou research. It is recommended that experts in related fields deepen their collaboration in the future, with the expectation of producing more high-level research results.

3.2.2. Collaborating Institutions

We imported the screened literature into the CiteSpace 6.4.R1 and selected the analysis of cooperative institutions, generating a total of 310 nodes (institutions) and 75 connections (cooperative relationships) (Figure 8). In the figure, the font size indicates the number of papers published by the institutions, and the lines represent the existence of cooperation between institutions. The color of the lines, according to the legend, indicates the years of collaboration between institutions, and the more lines there are, the closer the cooperation between the organization and other organizations.

Due to the large number of publishing organizations, we set the threshold for node labels to 2, and the figure shows the organizations with more than two published papers. At the same time, we have also compiled the names of organizations with more than five publications, the earliest publication time, and the number of publications into a table (

Table 2. Top 16 research institutions in the field of CQAH (including parallel rankings).

No.	Count	Year	Institutions
1	31	1996	Guangzhou University
2	29	1997	Huaqiao University
3	29	2010	Hainan University
4	27	2001	South China University of Technology
5	22	2013	Hainan Normal University
6	18	2007	Wuzhou College
7	13	2008	Tongji University
8	12	2012	Qinzhou College
9	11	2008	Guangxi Normal University
10	9	1999	Sun Yat-sen University
11	8	2006	Guangxi University
12	8	2003	Xi’an University of Architecture and Technology
13	8	2020	Xiamen University
14	7	2003	Guangdong University of Technology
15	7	2010	Huazhong University of Science and Technology
16	6	2016	Jiangxi University of Technology
17	5	2015	Haikou University of Economics
18	5	2010	Fuzhou University
19	5	2023	Hainan University of Science and Technology
20	5	2012	Shenzhen University
21	5	2016	Guangxi Arts Institute

).

As can be seen from the analysis chart of collaborating organizations (Figure 6), each node represents a university or research institution participating in Qilou research. Some larger nodes can be seen in the chart, such as “Guangzhou University”, “Huaqiao University”, and “Hainan University”. These organizations are core research institutions in this field, having published a large number of papers or possessing relatively high academic influence. Several distinct clusters of collaborating organizations have formed in the chart. There are many cooperative relationships among the organizations within these clusters. For example, the cluster of organizations around “Guangzhou University” and “Huaqiao University” shows that there is frequent cooperation among these organizations.

The spatial distribution of Qilou architecture exhibits a discernible regional characteristic, with research institutions predominantly adhering to the principle of proximity in the selection of samples. Collaborating organizations are dispersed across numerous provinces nationwide, including Guangdong, Guangxi, Fujian, Hainan, Shaanxi, Hubei, Hunan, and other regions, thereby underscoring the extensive geographical distribution of CQAH research. Most collaborating institutions are universities, such as Guangzhou University, Huaqiao University, Hainan University, and Xi’an University of Architecture and Technology. This highlights universities’ central role in CQAH research. Universities in the southern region have a comparatively higher number of publications, which are directly related to the rich Qilou architecture and abundant research resources in this area. Statistical analysis reveals a geographical disparity in the number of universities conducting Qilou research, with 30 universities located in coastal regions, compared to only 15 in inland areas. This trend is particularly pronounced in regions with dense Qilou architecture, such as Guangzhou, Xiamen, and Haikou, where local universities also exhibit a significant publication rate. The correlation between the number of publications and geographical location, as well as the distribution of Qilou architecture, is noteworthy.

The study shows clear signs of regional cooperation, with institutions like Huaqiao University and Guangzhou University playing a central and leadership role in the collaboration network. Furthermore, South China University of Technology has extended its collaboration with Fuzhou University and Huaqiao University. In addition to universities and research institutes, firms such as Haikou Tourism and Culture Investment Holding Group Co. Ltd. participate in the collaboration, demonstrating the trend of mixing industry, academia, and research. In the Qilou-related study, the cooperation network is more complicated, with many cooperation groups and cross-collaboration links, demonstrating the complexity of Qilou architectural heritage research.

The interconnections within the collaborative network reveal the multidisciplinary and cross-domain nature of the research on Qilou. This complex network also reflects the diversity of the research. Different research institutions and researchers conduct studies from their respective perspectives, enriching the content and methods of research on Qilou architecture. For example, some studies focus on the historical and cultural value of Qilou buildings, while others pay attention to the conservation and renewal techniques of these structures. There are also studies that explore the functional transformation of Qilou buildings in contemporary society. However, due to the distribution areas of Qilou, research in inland regions is relatively weak. The disparity in the number of studies between coastal and inland regions reflects differences in the geographical distribution of Qilou, economic foundations, research hotspots, historical and cultural backgrounds, policy support, and distribution of academic resources. These differences also significantly affect the depth and breadth of research on Qilou.

3.3. Analysis of Keywords and Key Issues

3.3.1. Analysis of Keyword Co-Occurrence

Keyword co-occurrence refers to the phenomenon where two or more keywords appear simultaneously. By analyzing the co-occurrence relationships of these keywords, we can reveal the themes and information characteristics of the literature, thereby analyzing the research directions and hotspots in a particular field [66]. We imported the selected literature into CiteSpace 6.4.R1 for keyword co-occurrence analysis, choosing frequency for keyword labeling, and generated a total of 441 nodes (keywords) and 826 connections (co-occurrence relationships), with a network density of 0.0085, indicating a good network structure. Due to the large number of keywords, we set the “Largest” parameter to 5, so the keyword co-occurrence analysis graph will display the largest five keyword connection networks (Figure 9).

The appearance years of the keywords range from 1996 to 2015, indicating a long time span for CQAH research and different research focuses in different years. In the figure, each node represents a keyword, and the size of the node indicates the frequency of the keyword’s appearance in the literature. The larger the node, the more important or common the keyword is in the research. The color of the node indicates the time according to the legend. The lines between the nodes represent the co-occurrence relationships between keywords, and the more lines there are, the stronger the association between the keywords. Additionally, we have compiled a table of the top 20 keywords in terms of co-occurrence frequency, from which the appearance year and centrality of these keywords can also be seen (

Table 3. The top 20 co-occurring keywords in the field of CQAH (including parallel rankings).

Count	Centrality	Year	Keywords
138	0.94	1996	Qilou
34	0.19	1999	Qilou Architecture
31	0.12	2000	Conservation
17	0.13	2003	Historic District
15	0.09	1999	Guangzhou
10	0.03	2002	Development
9	0.03	2015	Haikou Qilou
8	0.01	2007	Lingnan Qilou
8	0.03	2008	Haikou
7	0.03	2008	Urban Renewal
7	0.01	2001	Renovation
7	0.04	2008	Culture of Qilou
7	0.01	2012	Guangzhou Qilou
6	0.02	2012	Historic District of Qilou
6	0.02	1999	Culture
5	0.04	2005	Quanzhou
5	0.01	2004	Zhongshan Road
5	0.02	1996	Lingnan
5	0.02	2006	Architecture
5	0.05	2011	Heritage

).

Generally speaking, keywords with a high frequency of occurrence also have a high centrality, indicating that these keywords are of great importance and influence in the research network. In Table 3, the keyword with the highest centrality is “Qilou”, which has a centrality of 0.94, indicating that it is a core node in the research network and has many co-occurrence relationships with other keywords. Other keywords with relatively high centrality include “Qilou architecture” (0.19), “conservation” (0.12), and “historic district” (0.13), which also play important roles in the research network.

As shown in Figure 8, which presents the co-occurrence network of keywords, the top 10 keywords in terms of frequency are “Qilou” (138, 0.94), “Qilou architecture” (34, 0.94), “conservation” (31, 0.12), “historic district” (17, 0.13), “Guangzhou” (30, 0.09), “development” (10, 0.03), “Haikou Qilou” (9, 0.03), “Lingnan Qilou” (8, 0.01), “Haikou” (8, 0.03), and “urban renewal” (7, 0.03). From these keywords, we can identify the hot topics in CQAH research. Among them, “Guangzhou Qilou”, ” Haikou Qilou”, and “Quanzhou Qilou” are the core research objects. Keywords such as “commercial”, ” public space”, and “tourism” reflect the multifunctionality and value of Qilou architecture in economic, social, and cultural aspects. The appearance of keywords like “conservation”, “transformation”, and “renewal” indicates that Qilou architectural heritage is facing challenges of protection and revitalization, and researchers are exploring how to balance conservation and utilization. Keywords such as “urban planning”, “urban renewal”, and “block characteristics” show the role of Qilou architecture in urban development and planning, as well as how to protect and utilize these historical buildings through planning. Keywords like “neighborhoods”, “resident”, and “cultural heritage” reflect the impact of Qilou architecture on society and culture, as well as how to promote community development and cultural inheritance through the protection and revitalization of Qilou.

In the research network, keyword nodes act as bridges, connecting different research topics and fields. The term “Qilou”, as a core keyword, has a high centrality, indicating that research on Qilou has already formed a relatively systematic research system and has a high level of influence in the academic community. Other high-centrality keywords, such as “Qilou Architecture” and “Conservation”, are not only at the core of the research but also guide its direction and focus. With the increasing centrality of keywords like “Urban Renewal”, “Development”, and “Culture of Qilou”, future research is likely to focus more on the role of Qilou in urban development and cultural tourism. The analysis of keywords also shows that Qilou’s research involves not only architecture but also sociology, cultural studies, and other disciplines. This interdisciplinary research perspective helps to comprehensively understand and protect CQAH.

3.3.2. Analysis of Keyword Clusters

Keyword cluster analysis is based on keyword co-occurrence analysis, which uses statistical methods to conduct in-depth research on the co-occurrence relationships between keywords. The aim is to group closely related keywords, revealing the research clusters formed within the academic field. This process not only simplifies the complex co-occurrence network relationships but also helps researchers more intuitively observe the research hotspots and main directions [42,67].

In keyword clustering analysis, Latent Semantic Indexing (LSI) extracts clustering labels by analyzing the latent semantic relationships between documents. LSI can capture the underlying topics within the content of documents. Log-Likelihood Ratio (LLR) evaluates the importance of keywords in clustering by calculating their log-likelihood ratios. LLR is generally considered to have high accuracy and coverage in extracting clustering labels, and it can effectively reflect the uniqueness of the cluster and the research topics. Mutual Information (MI) extracts labels by measuring the strength of association between keywords and clusters. It can identify keywords highly relevant to the clusters, but may be less effective in recognizing rare keywords. In previous studies, LLR has been commonly recommended for generating clustering labels due to its uniqueness and good coverage.

We imported the selected literature into CiteSpace 6.4.R1 for keyword clustering analysis, generating 15 main clusters (Figure 10). The modularity Q is 0.6656, and the Weighted Mean Silhouette S is 0.8967, indicating that most of the clusters have good cohesion. The 15 main clusters of CQAH that we generated are specifically “0. Qilou”, “1. Qilou Architecture”, “2. Guangzhou Qilou”, “3. Development”, “4. Historical District”, “5. Guangzhou”, “6. Qilou Culture”, “7. Lingnan”, “8. Quanzhou”, “9. Beihai”, “10. Gray Space”, “11. Urban Renewal”, “12. Chuanjiao Xu”, “13. Landscape Architecture”, and “14. Regionalism”.

We have also organized the 51 clusters and their main keywords into a table (

Table 4. The 14 clusters of keywords for the field of CQAH.

Cluster-ID	Size	Silhouette *	Year	Label (LLR)	Label (LSI)	Label (MI)
0	82	0.939	2014	Qilou (16.73, 1 × 10−4); Zhongshan Road (9.32, 0.005); Qilou Architecture (7.62, 0.01); Overseas Chinese (6.98, 0.01); Renewal (6.98, 0.01)	(14.5) Facade; (14.42) Zhongshan Road; (13.65) Form; (12.43) Renovation and Upgrading; (11.55) Commercial	Sanbu town (1.33); Eave Wall (1.33); Qinzhou Qilou (1.33); Qilou Legislation (1.33)
1	41	0.68	2014	Qilou Architecture (47.39, 1 × 10−4); Qilou (14.42, 0.001); Exploit (9.17, 0.005); Development Motivation (9.17, 0.005); Morphological Typology (4.57, 0.05)	(20.78) Qilou Architecture; (9.84) Form; (9.61) Development Motivation; (8.69) Architecture; (6.44) Exploit	Morphological Typology (0.31); Integral (0.31); Reinforce (0.31); Architectural Character (0.31)
2	34	0.868	2013	Guangzhou Qilou (24.76, 1 × 10−4); Haikou Qilou (14.72, 0.001); Qilou (12.34, 0.001); Spirit of Place (9.77, 0.005); Architectural Form (9.77, 0.005)	(15.97) Guangzhou Qilou; (9.84) Haikou Qilou; (9.61) Spirit of place; (9.61) Architectural Form; (8.26) Guangzhou	Commercial district (0.26); Rurality (0.26); Symbolic Characteristics (0.26); Shuidong Street Qilou (0.26)
3	34	0.92	2009	Development (19.59, 1 × 10−4); Rehabilitation (16.6, 1 × 10−4); Conservation (14.31, 0.001); Lingnan Architecture (12.41, 0.001); Subtropical (12.41, 0.001)	(12.43) Lingnan Architecture; (12.43) Subtropical; (10.06) District; (9.61) Public Space; (9.61) District Characteristics	Utilization (0.42); Leisure Space (0.42); Landscape Analysis (0.42); Traditional District (0.42)
4	32	0.913	2011	Historic District (16.49, 1 × 10−4); Conservation Update (9.68, 0.005); Regional Character (9.68, 0.005); Wuzhou Qilou District (9.68, 0.005); Cultural Symbols (9.68, 0.005)	(10.7) Historic District; (10.06) District; (9.61) Conservation Update; (9.61) Regional Character; (9.61) Wuzhou Qilou District	Nanyang Overseas Chinese (0.27); Organic Renewal (0.27); Experience Preferences (0.27); Tourist (0.27)
5	27	0.932	2008	Guangzhou (15.15, 1 × 10−4); Historic Environment (9.96, 0.005); Architectural Form (9.96, 0.005); Qilou District (6.31, 0.05); Urban Context (4.96, 0.05)	(9.61) Historic Environment; (9.61) Architectural Form; (8.26) Guangzhou; (5.61) Revival; (5.61) Qilou District	Urban Context (0.24); Revival (0.24); Urban Culture (0.24); Veranda Style (0.24)
6	27	0.871	2009	Qilou Culture (16.33, 1 × 10−4); Urban Planning (10.83, 0.001); Guangxi (10.83, 0.001); Current Situation (10.83, 0.001); History (10.83, 0.001)	(12.43) Qilou Culture; (9.61) Urban Planning; (7.61) Wuzhou; (7.61) Guangxi; (7.61) Current Situation	Municipal construction (0.18); Wuzhou (0.18); Fire Safety (0.18); Geographical Imagery (0.18)
7	21	0.954	2007	Lingnan (13.99, 0.001); Architectural styles (6.93, 0.01); Function (6.93, 0.01); Modern City (6.93, 0.01); Garden (6.93, 0.01)	(4.97) Lingnan; (4.81) Architectural styles; (4.81) Modern City; (4.81) Garden; (4.81) Qilou system	Architectural styles (0.07); Function (0.07); Modern City (0.07); Garden (0.07)
8	19	0.968	2008	(12.43) Quanzhou; (9.61) Spatial Composition; (9.61) Stylistic Features; (5.61) Characteristics; (4.81) Comparison	Quanzhou (13.99, 0.001); Spatial Composition (13.99, 0.001); Stylistic Features (13.99, 0.001); Comparison (6.93, 0.01); Background (6.93, 0.01)	Comparison (0.07); Background (0.07); Orientation (0.07); Quanzhou Qilou (0.07)
9	8	0.983	2015	(9.61) Beihai; (4.81) Regional Economy; (4.81) Historical District; (4.81) Economic Interaction; (4.81) Planar Organization	Beihai (16.51, 1 × 10−4); Regional Economy (8.13, 0.005); Historical District (8.13, 0.005); Economic Interaction (8.13, 0.005); Planar Organization (8.13, 0.005)	Qilou (0.08); Regional Economy (0.03); Historical District (0.03); Economic Interaction (0.03);
10	7	0.971	2018	(9.61) Gray Space; (5.74) Space; (4.81) Cultural Connotation; (4.81) Citizen Life; (4.81) Pan-Space	Gray Space (16.51, 1 × 10−4); Cultural Connotation (8.13, 0.005); Citizen Life (8.13, 0.005); Pan-Space (8.13, 0.005); Form (8.13, 0.005)	Qilou (0.08); Cultural Connotation (0.03); Citizen Life (0.03); Pan-Space (0.03)
11	6	0.991	2007	(4.81) Urban Renewal; (4.81) Eaves; (4.81) Architectural Culture; (1.81) Architectural; (1.64) Culture	Urban Renewal (9.91, 0.005); Eaves (9.91, 0.005); Architectural Culture (9.91, 0.005); Qilou (0.47, 0.5); Protection (0.2, 1.0)	Qilou (0.1); Urban Renewal (0.02); Eaves (0.02); Architectural Culture (0.02); Protection
14	5	0.994	2011	(1) Regionality; (1) Guangdong; (1) Architectural Symbol; (1) Spatial Form; (1) Green; (1) Qilou	Regionality (9, 0.005); Architectural Symbol (9, 0.005); Spatial Form (9, 0.005); Green (9, 0.005); Guangdong (9, 0.005)	Qilou (0.09); Regionality (0.02); Architectural Symbol (0.02); Spatial Form (0.02)

* Silhouette (Weighted Mean Silhouette S) is a crucial metric for evaluating the quality of keyword clusters, with values ranging from −1 to 1. A Silhouette score greater than 0.5 suggests a reasonably effective clustering outcome, while a score exceeding 0.7 indicates a highly convincing and robust clustering result.

). It can be seen that the three clusters with the highest Silhouette S values are “14. Regionalism” (0.994), “11. Urban Renewal” (0.991), and “9. Beihai” (0.983). This indicates that the research on CQAH focuses on regionalism, urban renewal, and the protection of specific regions, which are key research focuses in academia.

3.3.3. Summary of Key Issues

Based on the keyword co-occurrence analysis and keyword clustering analysis, this paper has identified four key issues of CQAH. These issues include the distribution area and historical origin of Qilou, differences in regional characteristics of Qilou architecture, conservation and renewal of the Qilou historic district in urban development, and cultural inheritance and spatial activation.

(1) The distribution area and historical origin of Qilou. This topic is reflected in clusters 5, 8, and 9. Qilou architecture is widely distributed in China, and the spatial distribution characteristics of Qilou architecture have been a focal point of related research. A number of scholars have investigated the overall distribution characteristics of CQAH in terms of density and scale of development. They have concluded that Qilou is the most abundant in Taiwan and Guangdong and that it is mainly distributed in Chaozhou, Shantou, Zhongshan, and Foshan in Guangdong [16]. Some scholars, using the methods of human geography, have analyzed the regional differentiation characteristics of regionalized CQAH [68]. In 2008, Teng Lanhua posited that the distribution of Qilou in Guangxi is chiefly influenced by the economic radiation from Guangdong, with the majority of the population residing in towns along the river [26]. In 2013, Xue Ying argued that Qilou in the Lingnan region is predominantly found along the coast and decreases inland, and there are more Hakka sub-cultures in mountainous areas [69]. As a result, Qilou is less promoted due to traditional etiquette constraints, while in the Guangfu region and Chaoshan region, where overseas Chinese are dense, it has promoted the development of Qilou [69]. In 2021, Lin Xianhong and others argued that traditional Qilou on Hainan Island exhibits a coastal distribution pattern and that their form and scale are associated with economic development [70]. Consequently, it can be deduced that Qilou in China is predominantly concentrated in the South China region, encompassing the coastal areas of Guangdong, Guangxi, and Hainan Island.

The architectural origin of Qilou architecture is also another focus of attention. Although there are multiple academic perspectives on the origins of Qilou architecture, scholars agree that Qilou buildings are a hybrid product of Chinese and Western cultures, formed by the collision of local and foreign cultures. However, scholars have different understandings of the main body of the Qilou. Theories positing the origin of Qilou as a result of Chinese immigrants have been advanced, with parallels being drawn between Qilou and the traditional architectural form of Qilou in Southeast Asia. The colonial decree, in combination with the formation of the Chinese diaspora, has been identified as a factor in the return of Qilou to mainland China [11,67,68]. Some scholars also believe that the prosperity of Qilou is related to the urban renewal movement in the late Qing Dynasty [15,48], while the open architectural type of Qilou and the geographical scope of its spread are also related to the local hot, humid, and rainy geographical climate [68]. Current research on the historical origins of Qilou architecture mainly focuses on two aspects: the time of origin and the place of origin.

From the perspective of time of origin, the development of Qilou architecture includes the formative stage and the mature stage. Regarding the formative stage, based on the historical data from the “Quanzhou Architectural Annals”, Fang Yong deduced that the prototype of Qilou in the south might have appeared as early as the Tang Dynasty, with the pavilion-style shopfronts existing during the Dali period (827–835). Similarly, the “market corridor” or “gallery house” in the north was already in existence during the Song Dynasty [20]. In 1993, Japanese scholar Fujimori Terunobu posited that the architectural form of Qilou stemmed from the “Colonial Veranda Style.” He noted that since the term “Veranda” originates from the dialect of Beniapukur in India, it is surmised that this style was first constructed there by British colonists, who referred to it as a “veranda house” [71]. Regarding the mature stage, in 1822, Sir Raffles of the United Kingdom proposed the Qilou street pattern in Singapore’s Urban Development Plan to create pedestrian space and unify the street facades. Later, this street pattern was rapidly popularized in Singapore [72]. The Qilou form, on the other hand, was introduced to the southeastern coastal areas of China in the early 20th century [12]. Meanwhile, Qilou as an urban development strategy was proposed by Zhang Zhidong in 1889, and as a formal management system of the city in 1912 [11].

From the perspective of the place of origin, in 1996, Xie and Luo believe that the Qilou architecture culture in Beihai’s historical district was formed as a result of the forced input of Western culture under foreign colonialism. It evolved from mere imitation to later applying foreign architectural forms to traditional buildings and finally developed into a Qilou form with Chinese characteristics [10]. In 2005, Zhao Xiaobo believed that the foreign culture embodied by Xiamen Qilou architecture was brought about by imperialist invasion and the opening of trading ports. Its form imitates the style of the late Renaissance and is similar to the Chicago School [66]. In 2006, when Lin Lin explored the Guangdong Qilou, he argued that the culture of Qilou originated in the Mediterranean and that Qilou is the result of the spread of Mediterranean culture to the South Seas region [11]. In 2011, Liu believed that “corridor-style” architecture is not quite the same as Qilou, and Qilou should not be included in the category of corridor-style architecture. However, it cannot be denied that the two types are closely related [42].

(2) Regional variations in the architectural characteristics of Qilou. This theme is reflected in clusters 0, 1, and 14. Due to differences in geographical location, economic development level, cultural characteristics, and building functions, Qilou architecture has also exhibited unique regional characteristics in different regions, manifested in spatial form, facade features, and construction techniques.

From the perspective of spatial form, the modern local Qilou reflects its regionalism through spatial construction techniques. In Qilou architecture, traces of traditional spatial prototypes can be found, and under the new spatial order, Qilou guides users’ behavior and creates space experiences that adapt to the new environment. In 1996, Xie concluded that Qilou in Beihai City is a regional architectural form formed by the combination of traditional Chinese eaves corridor-style buildings and foreign Qilou culture [10]. In 2005, Professor Chen Zhihong focused on the southern Fujian region and believes that the Qilou style was initially inspired by foreign street planning models, integrated with local shop house forms, absorbed foreign styles and technologies, and formed a new Qilou style with unique regional characteristics. On the one hand, Qilou architecture has been accepted and improved by overseas Chinese hometowns due to local socio-economic needs and commercial models, becoming the main force for the improvement of traditional shophouses in southern Fujian and coastal areas of southern China, highlighting the key orientation of socio-economic needs for the transplantation of foreign buildings. On the other hand, Qilou in the overseas Chinese hometowns in southern Fujian has become a traditional space that integrates family ethics and Feng Shui aesthetic orientation after its introduction, which is a common result of the evolution of foreign cultural dissemination and regional integration [2,29,73].

In the study of the facade characteristics of Qilou architecture, Chen Zhihong’s team pointed out that the building materials, construction techniques, and related technologies of modern Qilou architecture in Zhangzhou are all based on local materials and have many similarities with traditional local architecture. They believe that the modern Qilou in Zhangzhou is a preliminary combination of modern foreign street planning models and local traditional street house forms. On this basis, further integration of foreign architectural styles and technological processes resulted in the formation of Qilou architecture with the unique regional characteristics of Zhangzhou [74].

In addition, Qilou architecture in different regions also utilized localized building materials and construction techniques. In 2014, Chen Zhihong and Li Jixiang conducted a material combination classification of modern Qilou architecture in Zhangzhou through field surveys and statistical analysis methods. They concluded that Qilou includes a variety of regionalized façade characteristics such as pure red brick, red brick with wooden walls, red brick with plaster, pure cement, and special styles [41]. In 2014, Zhao Aihua and her team explored the expressive forms of the plastering techniques used in Haikou Qilou architecture and pointed out that the plastering in Haikou Qilou is a unique local traditional craft formed with shell lime and paper pulp as raw materials [75]. Through her research on the regional differences in the styles of Guangzhou Qilou and Southern Fujian Qilou, Yao concluded that the construction of Guangzhou Qilou often employed the unique water-washed bricks of the Lingnan region. In contrast, Qilou in Southern Fujian predominantly used smoked bricks, reflecting the inheritance of the traditional “red brick culture” [76]. The research on the regional characteristics of Qilou reflects the profound influence of the local environment and cultural traditions on the development of this type of architecture. It demonstrates a dynamic and complex interactive mechanism. At the same time, it also shows that the introduction and development of foreign cultures must inevitably go through a process of adaptation and integration with local elements.

(3) Conservation and renewal of the Qilou historic district in urban development. As illustrated in clusters 2, 3, 4, and 7, this theme is reflected in the distribution of Qilou buildings. The conservation and renewal of Qilou historic districts in urban development focuses on physical repair, functional adaptation, and infrastructure upgrades. This approach aims to preserve their historical character while boosting modern usability. These buildings are predominantly located within historic districts, which are characterized by their abundance of historical information and cultural memory. A number of scholars have investigated the manner in which the Qilou historical neighborhood has absorbed both local and foreign cultural elements [68,74].

In 1998, Yuan Qifeng et al. researched the Qilou commercial streets of Tenth Fu Road and Shangxiajiu Road [77]. They found that preserving these Qilou commercial streets is important in maintaining the city’s traditional style. The positioning and transformation of the commercial layout of the Qilou streets are related to urban spatial planning [77]. In 2011, Chen pointed out that during the 2000 renovation of Haikou Qilou, the functions only underwent a simple replacement. This led to the disappearance of the previously diversified business models, preventing Qilou from showcasing its unique characteristics. This phenomenon was a result of the impact of contemporary commercial formats. Under such impact, the traditional commercial formats of Qilou were at a disadvantage, which was not conducive to the future development of Qilou [78]. From the perspective of cultural geography, in 2014, An discusses the rise, evolution, symbolism, and contemporary cultural value of Haikou Qilou, including the fact that Haikou was the gateway to Qiongya and that foreign trade brought great impetus to the development of Haikou. Therefore, he believes that Qilou is the result of the joint efforts of Nanyang overseas Chinese and local merchants. Another group of scholars discusses the transformation of the Qilou historic district from a traditional commercial and residential function to a modern multi-functional one and the impact of this transformation on urban space [79,80]. In 2018, academician Chang Qing talked about the conservation and regeneration design of Haikou Qilou, which integrates local and South China style elements and pays special attention to the façade doors, windows, walls, column piers, and other parts of the façade in the restoration to achieve the revival of the historical environment [3,81].

Qilou architecture in the old town areas faces the contradiction between protection and development in the process of urban renewal and reconstruction. In recent years, the construction of community memory and resident identity, as well as the significance of the Qilou historic district in residents’ lives, have become hot topics in the academic community [82]. In addition, some scholars have explored how to enhance the cohesion and cultural identity of Qilou historical districts through protection and revival [83].

The research on the conservation and renewal of Qilou districts primarily focuses on material restoration, functional adaptation, and the optimization of infrastructure. The goal is to preserve the historical appearance of Qilou while enhancing its modern usability. This theme reflects the need to balance the preservation of historical Qilou architecture with modern urban development. Simple functional replacement or excessive pursuit of economic benefits may lead to the disappearance of traditional business models and weaken the uniqueness of Qilou districts. Therefore, the conservation and renewal of Qilou districts need to find a balance between functional adjustment and cultural inheritance.

(4) Cultural Inheritance and Spatial Activation. This theme is reflected in clusters 6, 7, 10, and 11. Cultural inheritance and spatial activation focus on uncovering intangible cultural heritage and reusing architectural spaces. This approach ensures the continuation of historical value and the rebirth of contemporary functions. Qilou architecture not only bears the historical memory of the integration of diverse cultures but also serves as a vivid carrier for the inheritance and development of regional culture. In recent years, the attention to the cultural heritage and architectural revitalization of Chinese Qilou architecture has gradually increased among both the academic community and the broader society. Some scholars, based on existing research, have proposed models for the cultural heritage and protection of Qilou architecture. In 2017, Cui believed that the protection of Qilou should not only focus on its diverse and mixed spaces but also preserve the intangible cultural significance it has inherited and the localized sense of place [84]. In 2024, Gan Jing and others discussed the revitalization of CQAH from the perspective of urban design. They argued that it is necessary to establish landmark buildings to enhance the regional distinctiveness of Qilou Architectural Heritage [85]. Some scholars have proposed innovative development models for Qilou Architectural Heritage through conceptual design. For example, Hua suggested that Qilou could be used as a bridge for the integration of indoor and outdoor spaces in the urban pedestrian traffic system, as well as an innovative model for performance spaces, exhibition spaces, and urban squares in 2018 [86].

Other scholars have explored the direction of Qilou architectural revitalization based on practical project experience. In 2017, Jiang and Yu, taking Wuzhou’s Qilou as the research object, attempted to combine it with Wuzhou’s Liubao tea culture, exploring the possibility of Qilou serving as a display space for regional culture [87,88]. Other scholars have explored the sustainable development of Qilou from the perspective of spatial design and tourism development. In 2017, Zhu and Li took Haikou Qilou Old Street as the research object, constructed the S-TRM logical framework, and concluded that the development of Qilou heritage should consider multiple dimensions such as tourists, local residents, and managers [89].

However, the issue of property rights in the revitalization process of Qilou is a complex and significant problem that requires innovative mechanisms and collaborative efforts from multiple parties to resolve. Solutions such as property rights consolidation, green channels, and policy guidance are effective, but they may encounter challenges such as conflicts of interest, legal barriers, and insufficient funding during implementation. Future research and practice should further explore how to continue the historical value of Qilou architecture and regenerate its modern functions on the basis of clarifying property rights.

3.3.4. Timeline View of Keywords, Burst Keywords, and Research Trends

A keyword timeline view is a visualization method showing the development and changes of keywords in different periods. It intuitively reflects the research focuses and hotspots in various periods and helps summarize the evolution of research stages [35,39]. Based on the keyword clustering analysis, we generated a keyword timeline view (Figure 11).

Keyword burst analysis focuses on detecting sudden changes in keyword frequency within a specific time range in a particular research field. It reveals the potential topics that have been prioritized by researchers during that period. This method is useful for analyzing research hotspots and, through the clustering of high-frequency words and the trends in their frequency changes over time, can deeply explore the cutting-edge trends and dynamics in a research area [35]. We initially set γ [0, 1] at 0.2 with a minimum duration of 2, extracting 75 burst keywords. To define the scope of research, we categorize these keywords into six main classes: Urban Planning and Construction, Architecture and Style, Culture and Region, Development Strategies, History and Society, and Urban Cases. The analysis of keyword bursts indicates that relevant research has gradually increased since 1999. It can be considered that the research on CQAH was relatively balanced between 1994 and 1999. However, from 2012 to 2024, scholars have paid more attention to the research areas of urban planning and construction, as well as culture and region, particularly the discussion of Qilou cases in cities. Furthermore, we adjust γ [0, 1] to 0.4 while keeping the minimum duration at 2. Using CiteSpace 6.4.R1, we obtain the 19 most frequent burst keywords and conduct a time-segmented analysis of their burst intensity (Figure 12).

Combined with the analysis of keyword co-occurrence, keyword clusters, and the trend of annual publications in the preceding text, this paper divides the research on CQAH into four stages through the timeline view of keywords and burst keyword analysis. The research hotspots of each stage are summarized as follows.

Stage 1: Study of basic characteristics and historical background (1994–2000). As indicated in the previous text, research on Qilou architecture began in the 1980s [18], with in-depth studies starting in 1994 [90]. From 1994 to 2011, as China’s urbanization speeded up, many historical buildings and districts faced the conflict between preservation and development. Qilou, a unique architectural type, started to attract scholarly attention. Research on CQAH centers on the basic characteristics and historical background of Qilou architecture. From keywords like Qilou, architectural form, architectural style, historical district, and Guangzhou, it is evident that during this stage, research mainly focuses on descriptive studies of Qilou architecture’s basic characteristics, historical background, and regional distribution, as well as analyses of individual cases. The research methods predominantly involve the analysis of literature and historical materials.

Stage 2: Study of architectural origins and development motivation (2001–2007). After China joined the WTO and its economy developed rapidly, urban renewal and cultural heritage protection became hot-button social issues. Research into color architecture started to gain more scholarly attention. From keywords like verandah, regional culture, urban context, development drivers, and regional elements, it is clear that in this stage, scholars started to look into the origins, development drivers, and connection with urban development of Qilou architecture, and explore its forms and cultural importance in different regions. Research began to integrate multiple disciplines, like urban geography, architecture, and cultural studies, employing methods such as comparative and case-study research.

Stage 3: Protection and revitalization of cultural heritage (2008–2017). In the context of globalization and informatization, cultural heritage protection and urban sustainable development have become a global consensus. As a unique cultural heritage in China, Qilou architecture has received more attention in research. From keywords like urban renewal, renewal, strategies, leisure space, public space, and application, it can be seen that research in this stage focuses more on the protection of Qilou architecture heritage, its activation and integration with modern society, and the role and value of Qilou architecture in urban renewal. Related research has adopted more interdisciplinary methods, such as GIS spatial analysis, social surveys, and participatory planning, in order to gain a more comprehensive research perspective.

Stage 4: Diverse perspectives and multidisciplinary cooperation (2018–present). In the new era, the Chinese government has proposed “rural revitalization” and “new-type urbanization” strategies. Research on Qilou architecture, a vital link between tradition and modernity, in rural and urban areas, is now attaching more importance to its practical importance. From keywords like cultural symbol, development, historical building, renewal strategy, and urban memory, it is evident that this stage of research on Qilou focuses more on protection strategies, cultural inheritance, and spatial activation. Scholars explore the potential and paths of Qilou architecture in rural–urban development, cultural tourism, and community building. Research methods now include more innovative ones such as 3D laser scanning, VR and AR technologies, and big data analysis. Scholars’ research on CQAH shows diversified research perspectives and rich research content. Multidisciplinary integration is used to explore the sustainable development of CQAH.

In addition, the year of the appearance of the keywords reflects the evolution of the focus of the Qilou research field. In the early years (e.g., “Guangzhou” in 1999 and “preservation” in 2000), research focused mainly on the preservation and renovation of Qilou architecture, demonstrating an awareness of the basic value of Qilou architecture and the need for its preservation. Over time, the research has delved into the regional culture of Qilou architecture (e.g., “Lingnan architecture” and “subtropical” in 2003) and the role of Qilou in urban development (e.g., “Development” in 2002). In recent years, research has focused more on the cultural significance and historical value of Qilou (e.g., “historical buildings” and “Qilou culture” in 2017), as well as specific examples of Qilou in specific cities (e.g., “Haikou Qilou” in 2015 and “historical neighborhoods” in 2021). This suggests that scholars have shifted their research on Qilou from basic conservation to a comprehensive exploration of their cultural, historical, and social values.

Overall, CQAH research has evolved from preliminary exploration to a process of multidisciplinary integration, with research content ranging from basic characterization to cultural heritage preservation, to adaptive use and sustainable development, and research methodology ranging from a single literature analysis to multidisciplinary cross-cutting and technological innovation.

4. Discussion

By analyzing the distribution characteristics, collaborative characteristics, keywords, and key issues of the CQAH literature, this paper suggests that researchers from different disciplines can prioritize the following four elements to focus on the future research direction of CQAH in the future.

4.1. Correlation Between Southeast Asia and Qilou in Overseas Chinese Hometowns

Qilou districts in Southeast Asia serve a diverse range of ethnic groups, including Chinese, Malays, and Indians. These multi-ethnic spaces reflect the complex social structure of colonial cities. In contrast, Qilou architecture in Chinese overseas hometowns is a product of the integration of traditional Chinese clan concepts and modern needs. Qilou architecture is widely found in Southeast Asia and southern China. Malaysia is considered the origin of Qilou architecture in Southeast Asia. In southern Fujian, the Qilou culture of overseas hometowns, propelled by the wave of Nanyang overseas Chinese returning to their hometowns in modern times, gradually merged with local traditional culture. This integration has profoundly influenced the development of Qilou architecture in southern Fujian [16].

In recent years, scholars have gradually attached importance to digital research and new technology applications of Qilou in Southeast Asia and China, and these research directions have become new trends due to the development of technology. In 2020, Kim, while discussing Chinese Europeanized architecture, noted that the spatial layout of the Bamboo Stretched Houses in Guangdong is identical to that of shophouses in Southeast Asia [91]. In 2023, Ruan Kaiyin employed VR and mapping techniques to create 3D models of Qilou, thereby applying digital technology to cultural heritage protection and disrupting the traditional methods used in museums and historical sites. In this study, scholars used Qilou in Southeast Asia and southeastern China as practical objects, developed online 3D prototypes, and visualized the spread of Qilou in different regions through online maps, presenting the spatiotemporal distribution characteristics of Qilou spread [92]. This highlights that Qilou buildings in Southeast Asia and China are frequently used as comparative groups in research, revealing a significant correlation between the two (Figure 13).

As mentioned earlier, CQA is mainly distributed in the southern region of China. Qilou buildings in these areas reflect their unique regional culture and the background of overseas Chinese hometowns, showcasing cultural diversity in building facade design, floor plan layout, and structural design. Qilou architecture in Guangzhou and Taishan, introduced by overseas Chinese from Nanyang and integrated with local culture, retains the colonial arcade style in its facade while incorporating distinctive Cantonese elements such as Manchurian windows and gray-sculpted ao-fish ridges [93]. Qilou architecture in Beihai, a hometown of overseas Chinese in Guangxi, combines Southeast Asian sun-shading eaves technology with the arcade space of the Lingnan region. The ground-floor colonnades often incorporate a combination of Vietnamese ironwood and Qinzhou blue bricks, a skill inherited from overseas Chinese [94]. Qilou architecture on Hainan Island places greater emphasis on ventilation and heat dissipation, with more streamlined facade designs. It also incorporates architectural elements from Nanyang, such as Nanyang-style louvered grilles and shutter systems [95]. As an architectural form with a cross-cultural background, Qilou has significantly different trajectories of dissemination and development across various countries and regions. For instance, in China, Qilou is primarily influenced by both Lingnan culture and South Asian culture, while in Southeast Asia, it integrates more local ethnic characteristics and Western architectural elements [96].

Some scholars have already explored the connections between Southeast Asian and overseas Chinese hometown Qilou architecture from perspectives such as cultural forms, sociology, history, and anthropology. In 2005, Chen Zhihong argued that modern Qilou in southern Fujian is the result of the conflict and integration between traditional local culture and foreign cultures. Qilou streets were developed under foreign influence, concurrently with urban renewal projects such as widening roads. They represent a method of unified planning, renovation, and construction of traditional shophouses, and the process of Western influence extends beyond the facades [73]. In 2021, Wang Junjie conducted research on the functional diversity of modern Qilou architecture in Penang and compared it with that of southern Fujian. He believes that the form of modern Qilou architecture in Penang was very likely influenced by traditional Chinese shophouses [16].

In the study of CQAH, the exploration of the culture of overseas Chinese hometowns and native place culture helps to reveal the mechanisms of folk cultural transmission. Therefore, this article argues that while researching the social history of overseas hometowns, greater attention should also be paid to overseas Chinese and their cultures in Southeast Asia. It is proposed that future research on CQAH should be an enhanced investigation into the various connections between Qilou in Southeast Asia and Chinese overseas hometowns, focusing on the dynamic development process of Chinese Qilou architecture driven by overseas Chinese and remittances. By comparing the regulatory systems and construction techniques of Qilou architecture in Penang, Malacca, and the southern Fujian and Guangdong regions, related research expands the field of research on the architectural history of modern overseas hometowns and clarifies the cultural genealogical relationships. The exploration of their interconnections needs to be carried out from multiple dimensions, breaking through national and disciplinary barriers to construct a multidimensional analytical framework of “architectural form–cultural network–social transformation.” This approach will allow us to reinterpret the transnational heritage value of Qilou architecture.

4.2. Constructing a Spatial Vitality Evaluation System for Qilou Architectural Heritage

Qilou, as an important part of the urban neighborhood, reflects the development lineage of the city and the lifestyle of its residents and is an important part of the urban fabric. Qilou, through its open ground floor space, provides citizens and tourists with shelter from the sun and rain, as well as a place for communication and interaction, thus reflecting the vitality of the city’s commercial and residential public space and the frequency of social interaction. However, existing studies on Qilou architecture mainly focus on its historical value, architectural features, and cultural characteristics [51,63,79,80,85]. Existing Qilou research predominantly centers on historical and cultural heritage, with scant exploration of current spatial use. Meanwhile, CQAH faces issues like spatial decay, functional disorder, low utilization, and a lack of systematic research on a spatial vitality evaluation system.

Utilizing multi-source big data, such as mobile signaling data, street view image data, and POI data, can provide a basis for research related to the spatial vitality distribution characteristics of Qilou across different time dimensions. Based on our team’s ongoing research on the spatial vitality characteristics of Qilou architectural heritage in different regions of China, we have found that the majority of Qilou architectural heritage spaces face the issue of overly concentrated high-vitality periods, leading to a disordered vitality in the Qilou and its surrounding areas (Figure 14). Specifically, the development of Qilou historical districts has spurred rapid commercial prosperity and a significant increase in tourist flow. However, high-vitality periods are primarily concentrated on holidays or specific commercial hours, forming a stark contrast with the vitality values on weekdays, resulting in a highly uneven temporal distribution of spatial vitality. This vitality disorder has many adverse effects on Qilou architectural heritage and its surrounding areas. For example, during non-high-vitality periods, the space appears desolate, with low resource utilization rates, making it difficult to fully demonstrate its comprehensive value in history, culture, commerce, and other aspects. During high-vitality periods, the surrounding areas face problems such as traffic congestion and environmental noise, leading to a decline in residents’ quality of life and restricted overall development.

In this study, the heat maps of the three Qilou history streets reveal three classic cases, with high-heat areas displaying three distinct forms: point, line, and surface. The first type is characterized by a point distribution, exemplified by the Haikou Qilou. For the Qilou area and its surroundings, this pattern can lead to traffic congestion at the intersections between the Qilou area and the surrounding regions, causing traffic management pressure to increase rapidly during specific periods. Within the Qilou area, it is necessary to implement regional traffic restrictions during peak hours. In high-density areas, crowd management and infrastructure support should be enhanced based on actual needs, and increased supervision, protection, and maintenance of the Qilou buildings are also required. The second type is a linear distribution, such as the Xiamen Qilou. For the Qilou area and its surroundings, traffic management at the entrances and exits of the area needs to be strengthened, as well as the management of vehicles transporting tourists. Within the Qilou area, crowd management and safety measures should be enhanced, and improvements to traffic and infrastructure facilities are necessary to increase the convenience for tourists and residents. The third type is a surface distribution, like the Guangzhou Qilou. For the Qilou area and its surroundings, the Qilou district serves not only as a tourist attraction but also as a part of residents’ daily lives. It is necessary to coordinate the relationship between tourists and local residents to avoid mutual disturbance and maintain the normal order of residential areas. Within the Qilou area, zoning can be implemented to prevent visitor fatigue, and appropriate rest areas can be set up to enhance the comfort of sightseeing. Heat maps as one of the indicators in the research on the prediction system of Chinese Qilou architectural heritage can be supplemented and verified by other diverse methods in the future.

Thus, this article suggests creating a scientific spatial vitality evaluation system for Qilou Architectural Heritage. This will comprehensively assess its function and value in modern cities, offering a scientific basis for urban planning and Qilou protection. Moreover, this system can analyze the current vitality of heritage sites, spot spatial use conflicts (e.g., business format homogenization conflicting with traditional styles), develop precise protection strategies, prevent homogeneous renovation, and achieve sustainable heritage revitalization and local cultural identity reshaping.

Previous studies on urban spatial vitality assessment have used qualitative methods to measure the vitality characteristics of architectural spaces or neighborhoods by using tourist satisfaction ratings, cell phone, and social media data, but the relevant data are too macroscopic and do not cover all age groups [97,98,99]. Secondly, in terms of quantitative methods, the least squares method, Pearson correlation analysis, multiple linear regression models, and geographically weighted regression models have been used to explore the factors influencing the spatial vitality of CQAH. However, most existing evaluation indicators focus on environmental, transportation, and facility variables, neglecting the impacts of socioeconomic and historical–cultural factors on the vitality of urban public spaces [100,101].

Therefore, for the construction of the evaluation system of the spatial vitality of CQAH, this article also recommends more exploration based on the previous methods of urban spatial vitality evaluation. To build a qualitative evaluation system for the spatial vitality of CQAH, this article suggests using the “Public Space & Public Life Survey” (PSPL) method to assess the quality of public spaces and the living conditions of residents in CQAH [102,103,104]. “Bottom-up mapping” visualizes the complexity and richness of spatial vitality. It offers a bottom-up data collection approach to compensate for macro data [105,106]. For constructing a spatial vitality evaluation system for Qilou architecture heritage by means of quantitative research, this article suggests incorporating newer spatial regression techniques such as multi-scale geographically weighted regression (MGWR). MGWR improves the classical geographically weighted regression by allowing different bandwidths for each variable, which in turn yields more plausible estimation results [107,108]. Select factors representing the spatial vitality of Qilou architectural heritage from sensory, social, economic, and cultural dimensions. Then, develop a comprehensive CQAH spatial vitality evaluation system.

4.3. Constructing a Prediction System for Qilou Built Environment and Sustainable Development of Qilou

The sustainable development of Qilou architecture faces many complex and multi-dimensional challenges and opportunities. On the one hand, CQAH carries rich historical and cultural connotations, witnesses the development and changes of cities and the evolution of social life, and its value cannot be ignored [56,57,85]. On the other hand, the acceleration of urbanization, changes in people’s lifestyles, and the impact of modern commercial activities have created conflicts between the conservation and development of Qilou neighborhoods. At the same time, the re-planning of urban space may lead to the disharmony between Qilou architecture and the surrounding environment, the aging of some Qilou buildings, insufficient funds for their protection, and the public’s biased perception of the value of Qilou [109,110].

At the architectural level, natural aging and human-induced damage have compromised the appearance of Qilou buildings. Many Qilou, due to their age, suffer from prominent issues such as wall cracks and decayed wooden components. Additionally, excessive renovations and the lack of uniform restoration standards have led to some Qilou losing their original character after modifications.

At the street level, Qilou streets suffer from a lack of functional diversity, severe commercial homogenization, and a dearth of distinctive features. The commercial activities in these areas are predominantly traditional snacks and general merchandise, which fail to enhance the tourist experience. Moreover, the width of the space under the Qilou eaves is generally insufficient, creating traffic bottlenecks. The situation is further exacerbated by merchants occupying Qilou spaces and the haphazard parking of pedestrians and vehicles, intensifying traffic congestion in these areas.

For the surrounding regions, Qilou streets often cover major urban thoroughfares, mostly located in old city districts with minimal buffer space between them and adjacent areas, leading to traffic congestion in the vicinity. Furthermore, there is a noticeable conflict and disconnect between the appearance and function of arcade streets and their surroundings. For example, in Guangzhou, the negative impact of modern urban development has resulted in poor harmony between Qilou streets’ surrounding environment (Figure 15).

These issues not only undermine the historical and cultural value of Qilou but also hinder its sustainable development. Addressing them through scientific planning and proper conservation is urgently needed.

Therefore, while preserving the historical and cultural values of CQAH, in order for the Qilou to better adapt to new demands and realize sustainable development, this article suggests constructing a prediction system for the future development of the Qilou and its built environment from the perspective of the full spatial vitality life cycle, so as to ensure that the effect of the spatial vitality of the Qilou in the sustainable development of the town is positive. Consequently, for constructing the prediction system of Qilou’s built environment, this article proposes the following three strategies:

Strategy 1: By using the XGBoost model to analyze the nonlinear correlation between the built environment of Qilou and the travel frequency of the target population, researchers can predict the optimal walking routes for pedestrians. Therefore, this article suggests that researchers consider day and night, weekdays and weekends, and seasons as temporal dimensions, and incorporate different types of Qilou and various areas as spatial dimensions for comprehensive analysis, to form the foundational data for predicting the built environment of Qilou. XGBoost can analyze feature importance to identify the most influential factors on travel frequency. These factors may include the width of the arcade walkway, street width, traffic density, and surrounding facilities. This analysis can inform future planning and strategies. Moreover, XGBoost can predict optimal walking paths to boost traffic efficiency, helping pedestrians avoid congested areas and enhance the utilization of Qilou traffic spaces [111].

Strategy 2: Researchers can use the GIS-CA model to plan the optimal locations for the vehicular systems around Qilou, considering the natural environment, terrain, transportation demand, and social impact. The GIS-CA model can also provide a reference for land use and spatial layout around the Qilou area based on land use changes, thereby enhancing the rationality of the functional layout of the Qilou area [112,113].

Strategy 3: Through on-site microclimate measurements and numerical simulation software like ENVI-met, researchers can simulate thermal comfort under different design schemes and optimize the design of Qilou architecture, such as adjusting building orientation and adding shading facilities. Therefore, this article suggests using physiological isotherms (PET) as indicators of human thermal comfort and proposing adaptive design strategies to improve thermal comfort. ENVI-met can simulate the 3D wind field in the Qilou area, including the distribution of wind speed and direction, to help analyze the ventilation situation of Qilou architecture. This analysis can optimize the ventilation design of Qilou architecture, such as adjusting the building layout and adding ventilation openings, to improve the ventilation effect [114,115].

Through these methods, researchers can explore whether Qilou’s built environment and surrounding town space can maximize their potential for sustainable development in the future. They can also evaluate and adjust Qilou’s built environment in light of the relevant predictions.

4.4. Digital Preservation of Qilou Architectural Heritage and Cross-Disciplinary Collaboration

At the neighborhood level, digital conservation can integrate the spatial data of the whole neighborhood and assist in planning and management. Qilou architecture faces many challenges in the development of modern society. On the one hand, its complex spatial structure makes it difficult for traditional conservation means to record and manage its detailed information comprehensively. On the other hand, land development, aging of buildings, and insufficient cultural awareness in the process of urbanization have made the conservation situation of Qilou architecture increasingly severe. Digital technology provides efficient and accurate support for the conservation of Qilou Architectural Heritage. It effectively addresses the loss of information and unclear restoration standards inherent in traditional conservation methods.

Although the Qilou architecture historic district belongs to an area with mixed town functions, this article suggests that detailed spatial information about the Qilou architecture can be quickly obtained through high-precision 3D laser scanning and low-altitude remote sensing by drones to form a complete digital archive [116,117,118]. Related scholars can utilize digital twin technology to build a virtual model of Qilou architecture to realize an integrated solution of “monitoring, restoration, and conservation”, which will support the long-term conservation of Qilou cultural heritage [119,120]. This article also suggests reconstructing the innovative mode of “digital + cultural creativity” in the traditional mixed commercial and residential Qilou neighborhoods through VR and AR technologies and combining the digital achievements of Qilou architecture with cultural and creative industries, so as to develop products and services with cultural value and market potential [121,122,123].

Digital conservation techniques can be applied not only to CQAH but also to other types of buildings. Vernacular buildings and dwellings are so scattered and numerous that traditional conservation methods are costly and inefficient. Digital means can systematically record architectural details, which are conducive to subsequent research and restoration. For example, by establishing a database through digitization, scholars can quickly retrieve and analyze building features. This promotes academic research and conservation work and facilitates later data statistical management and development utilization. More importantly, through data analysis, scholars can predict the aging conditions of buildings to develop preventive maintenance strategies and promote the sustainable development of architectural heritage.

Qilou Architectural Heritage is located in urban and rural areas, featuring both commercial and residential functions. Its development is multi-dimensional and complex, beyond the scope of a single discipline. Current Qilou research mainly focuses on architectural science and engineering. In the future, this article suggests a multi-disciplinary approach:

• Architecture and Urban Planning: Focus on spatial form to develop construction strategies for Qilou heritage.
• Geography: Emphasize theoretical analysis and quantitative methods to create dynamic monitoring and evaluation systems for CQAH.
• Sociology and Anthropology: Highlight human-centered approaches, studying residents’ and tourists’ behavior to establish optimization strategies for connecting CQAH with specific groups.

5. Conclusions

Using CiteSpace 6.4.R1 as a research tool and China Knowledge Network as a core database, this paper conducts a visual analysis and overview of the research related to CQAH, aiming at accurately and intuitively elaborating the literature distribution characteristics, collaborative characteristics, key issues, research trends and hot spots of the related research, and suggesting the future research direction of CQAH. The following conclusions are drawn (

Table 5. The synoptic table of research on CQAH.

Concept		Concept Explanation	Inference	Evidence
Research subject	Qilou (Theme = “Qilou architecture” Or “Qilou Street”, and the Title = “Qilou”)	Qilou is divided into arcade units with columns as the facade. The continuous space formed by the arcade is presented in the form of streets, and the streets form blocks.	The study conducted a search and screening on the China National Knowledge Infrastructure (CNKI) platform. Initially, a total of 616 documents were obtained, including 404 journal articles and 88 theses. During the research process, the data was screened again to ensure that each document contained information such as the author, institution, keywords, abstract, and publication date. This resulted in a final sample of 491 valid documents.
CiteSpace Parameter Settings *	The year per slice was set as 1	Slice Overlap = 0, which means that the time slices do not overlap. This ensures the independence of the time slices and makes the analysis results clearer.	The node type was set as author/institution/keyword, and collaborative characteristics is a term used to describe the key attributes or behavioral patterns manifested during the collaborative process.	CiteSpace 6.4.R1 analyzes literature by keywords, authors, etc. During analysis, select the node type (e.g., author, keyword) accordingly.
The Literature Distribution Characteristics	The Trend of Annual Publications	The number of papers issued can be indicative of the accumulation of knowledge and depth of research in research field of Qilou.	CQAH research spans four stages: from rising to stability; The number of publications has stabilized since 2008, and the majority of papers were published after 2008.	Stage one (1994–2000) featured a stable, low publication rate of 1–6 articles annually, with a minor peak in 1996. Stage two (2001–2007) saw a steady rise in publications and growing interest. Stage three (2008–2017) had the most significant growth, with articles increasing from 16 in 2008 to 41 in 2017. The final stage (2018–2024) maintains consistent activity, showing sustained interest [1,12,15,20,29,53,56,69,70,76,90,104].
	Source Disciplines of the Literature	Discipline distribution analysis can help researchers understand the main subject areas of Qilou research, thereby determining the direction and focus of future research.	The research on Qilou covers 20 disciplines. Most of them are majoring in Architecture Science and Engineering (46%)	The literature that has a considerable impact includes Xie, Yang, Fang among others [2,13,15,17,20,62].
	Source Publications of the Literature	Analyzing the publications of Qilou literature can help us understand research hotspots and trends, provide directions for future research, and promote academic development and cultural heritage protection.	Huazhong Architecture (16), Urbanism and Architecture (15), Chinese and Overseas Architecture, South Architecture, and Huaqiao University publications (12). Covering multiple dimensions such as history, culture, and technology.	[2,55,74,76,77,85].
Analysis of Collaborative Characteristics	Collaborating Authors (Frquency; Year)	Analyzing the collaborative features of Qilou’s literature can help reveal the cooperation model and academic influence in the research field and promote interdisciplinary cooperation.	Academic research: the studies of academicians Chen Zhihong, Lin Chong, and Lin Lin, etc. Practical research: the contributions of academician Chang Qing, Fang Yong, and Zhang Jie, etc.	Chang Qing, Liu Tao, Song Yang, Wang Hongjun, Zhao Aihua, Dai Shibing; Lin Lin, Ma Yutian, Gan Jing, Zhang Qingxi, Zhong Zhiping et al.; Yang Honglie, Chen Lixin, Cai Shiqian et al.; Yu Haomiao, Yang Sisheng, Wang Shan et al.
	Collaborating Institutions		Centered around Guangzhou University, Huaqiao University, and Hainan University. The research samples were selected from nearby locations.	Some universities have a deep accumulation of research in this field: Guangzhou University (1996, 31), Huaqiao University (1997, 29), Hainan University (2010, 29), South China University of Technology (2001, 27), Hainan Normal University (2013, 22).
Analysis of Key Word	Centrality (Top 5) (Time, Centrality, Count)	Keywords are a high-level summary of the core content of the literature, which can reflect the main direction and hot spots of the research. Through keyword analysis, we can quickly grasp the current status and development trend of Qilou research and reveal the internal connection between different research topics. Further clustering of keywords can classify keywords, thereby identifying the main research directions and hot areas in Qilou research.	Qilou (1996, 0.94, 138); Qilou Architecture (1999, 0.19, 34); Conservation (2000, 0.12, 31); Historic District (2003, 0.13, 17); Historic District (1999, 0.09, 15).	[12,13,21,23]
	Hotspot topics in research		Multifunctionality and Value for Multiple Parties; Challenges and Strategies for Conservation and Activation; Arcades and Urban Relationships; Community Development and Cultural Heritage.
	Clustering Analysis (LLR *)		“0. Qilou”, ”1. Qilou Architecture”, ”2. Guangzhou Qilou”, ”3. Development”, ”4. Historical District”, ”5. Guangzhou”, “6. Qilou Culture”, ”7. Lingnan”, ”8. Quanzhou”, ”9. Bei-hai”, ”10. Gray Space”, ”11. Urban Renewal”, ”12. Chuanjiao Xu”, ”13. Landscape Architecture”, and “14. Regionalism”.
Analysis of Key Issues	The distribution area and historical origin of Qilou	Qilou architecture is widespread in China. Its spatial distribution characteristics have been a research focus. Scholars have studied its density and scale and analyzed regional differentiation using human geography methods.	Distribution Area: In the South China region, encompassing the coastal areas of Guangdong, Guangxi, and Hainan Island. Historical Origin: A hybrid product of Chinese and Western cultures, formed by the collision of local and foreign cultures. Scholars have different understandings of the main body of the Qilou (time of origin, and place of origin).	This topic is reflected in clusters 5, 8, and 9 [10,15,20,24,26,39,42,48,59,68,70,71,72].
	Regional variations in the architectural characteristics of Qilou.	Due to differences in geographical location, economic development level, cultural characteristics, and building functions (spatial form and facade characteristics)	Modern local Qilou shows regionalism via spatial construction techniques. It retains traditional spatial elements, guides user behavior, and adapts to new environments. Local materials and techniques are used in regional Qilou. Research on Qilou’s regional characteristics shows the local environment and cultural influence, a dynamic interaction mechanism, and the adaptation and integration of foreign cultures with local elements.	This theme is reflected in clusters 0, 1, and 14 [13,17,73,74,76].
	Conservation and renewal of the Qilou historic district in urban development	Qilou conservation focuses on repair, functional adaptation, and infrastructure upgrades to preserve historical character and enhance usability. These buildings, rich in history and cultural memory, are mainly in historic districts.	Recent studies focus on community memory, resident identity, and the significance of Qilou districts. Conservation efforts emphasize material restoration, functional adaptation, and infrastructure optimization to balance historic preservation with modern usability. Avoiding simple functional replacement and excessive economic pursuit is key to maintaining traditional business models and cultural uniqueness.	As illustrated in clusters 2, 3, 4, and 7, this theme is reflected in the distribution of Qilou buildings. This theme reflects the need to balance the preservation of historical Qilou architecture with modern urban development [3,68,77,78,82,83].
	Cultural Inheritance and Spatial Activation	Cultural inheritance and spatial activation aim to uncover intangible heritage and reuse spaces, ensuring historical continuity and contemporary functional rebirth.	The attention to the cultural heritage and architectural revitalization of Chinese Qilou architecture has gradually increased. Proposed models for the cultural heritage and protection of Qilou architecture, and explored the direction of Qilou architectural revitalization based on practical project experience.	This theme is reflected in clusters 6, 7, 10, and 11. Cultural inheritance and spatial activation focus on uncovering intangible cultural heritage and reusing architectural spaces [88,89].
Research Phase Division	Timeline view of keywords (Four Stages)	Timeline analysis can intuitively display the evolution of research topics over time, helping researchers track the dynamic changes in research hotspots and also identify the cutting-edge directions in research fields.	Stage 1 1994–2000: Study of basic characteristics and historical background.	The formula for burst term detection is based on Kleinberg’s algorithm, which identifies research frontiers by calculating the growth rate of word frequency * and statistical significance (p < 0.05).
			Stage 2 2001–2007: Study of architectural origins and development motivation.
	Burst Keywords (γ * = 0.2 with a minimum duration of 2)	Burst keyword analysis can identify research hotspots that have received high attention during specific time periods. The higher the burst strength, the higher the attention the keyword has received during the corresponding period.	Stage 3 2008–2017: Protection and revitalization of cultural heritage.	$*\mathrm{B}\mathrm{u}\mathrm{r}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{n}\mathrm{e}\mathrm{s}\mathrm{s}=\mathsf{\gamma }\times {\displaystyle \frac{\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{c}{\mathrm{y}}_{\mathrm{t}+1}-\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{c}{\mathrm{y}}_{\mathrm{t}}}{\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{c}{\mathrm{y}}_{\mathrm{t}}}}$
			Stage 4 2018–Present: Diverse perspectives and multidisciplinary cooperation.
Notes	* CiteSpace Parameter Settings: CiteSpace performs bibliometric analysis and knowledge graph visualization of literature by adjusting a series of parameters, including time slicing, node types, thresholds, and pruning, among others. * The likelihood ratio (LLR) algorithm is one of the core algorithms of CiteSpace. This algorithm evaluates the significance and relevance of keywords in a specific research field by calculating their frequency of occurrence in different documents. This means that the LLR algorithm can be used to measure the association between keywords. * Burstiness indicates the intensity of a keyword’s emergence during a certain period. * Frequency refers to the occurrence rate of a keyword at a specific point in time. * γ is a tuning parameter with a value range of [0, 1], which controls the cost of state transitions. (The choice of γ value needs to be adjusted according to specific research needs and data characteristics, and it is inversely proportional to the number of burst terms.)

).

This study finds that research on Qilou has evolved from the early focus on architectural form and historical origins to a broader range of multidimensional issues, including cultural inheritance, urban renewal, and spatial activation, showing a clear trend of interdisciplinary integration. However, current research still has certain limitations, such as imbalanced regional studies, an incomplete theoretical system, and insufficient application of digital preservation technologies. Therefore, this paper suggests that researchers prioritize the following four research directions of Chinese Qilou Architectural Heritage in the future:

• Correlation between Southeast Asia and Qilou in overseas Chinese hometowns. Researchers can explore the interplay between Qilou in Southeast Asia and overseas Chinese hometowns in terms of cultural dissemination, architectural form, and social structure. It is recommended that researchers deepen transnational comparative studies through a multidisciplinary perspective.
• Constructing a spatial vitality evaluation system for Qilou architectural heritage. Researchers can utilize multi-source big data and both quantitative and qualitative methods to establish a scientific evaluation system, which can address the imbalance of spatial vitality in Qilou and guide sustainable revitalization.
• Constructing a spatial vitality evaluation system for Qilou architectural heritage. Researchers can predict the future adaptability of Qilou and optimize its spatial functions and thermal comfort using technologies such as XGBoost, GIS-CA models, and microclimate simulation.
• Digital preservation of Qilou architectural heritage and cross-disciplinary collaboration. Researchers can employ 3D scanning, digital twin technology, and VR/AR techniques to achieve precise conservation. They can also collaborate across multiple disciplines, including architecture, geography, and sociology, to promote innovative research and practice.

However, this study has several limitations. For example, the literature related to CQAH is distributed in CNKI, so we conducted this study in the context of Chinese academic research, mainly choosing CNKI as the core data for this paper. However, this database does not provide readers with a broader global range of data on Qilou architectural heritage, and we also look forward to future disciplines conducting more extensive global research on Qilou heritage. In addition, we conducted this review after a detailed data collection procedure. However, to more accurately retrieve other documents, it will be necessary in the future to refine and accurately modify the selected keywords and data collection procedure.

CQAH, as a unique mixed-function building in Chinese urban and rural areas, not only embodies rich historical and cultural connotations but also holds irreplaceable significance in modern urban development and cultural heritage preservation. Its unique combination of commercial and residential forms and distinctive regional cultural characteristics have made it an important witness to the development of Chinese cities and towns. In recent years, with the acceleration of urbanization and the enhancement of cultural heritage protection awareness, the protection and adaptive use of Qilou architecture has received more and more attention. However, the study of Qilou architecture still faces many challenges. We expect that future research will pay more attention to the regional cultural characteristics and modern functional needs of CQAH and provide more targeted and forward-looking strategies for the conservation and revitalization of Qilou architecture through multidisciplinary synergistic innovation. At the same time, with the combination of digital technology and cultural and creative industries, CQAH is expected to be revitalized in the new era and become an important link between tradition and modernity, culture and economy.