Knowledge Reuse in Product-Service Systems

: The current study examines knowledge reuse (focused on the recipient) from a product life-cycle perspective in the context of product-service systems through 27 semi-structured interviews in 11 ﬁrms. This study focused on the phases of the beginning-of-life (represented by R&D, purchasing, and production) and the middle-of-life (represented by logistics, customer service/quality, and sales). Similarities and differences were found between and within the two phases and the six sub-phases. Our research suggests that to remain competitive, a consistent understanding of the knowledge requirements for both sender and recipient should be identiﬁed, a match between the knowledge sourced and the mechanism employed should be made, and organizational culture/mechanisms to retain higher-caliber employees should be prioritized.


Introduction
Severe challenges, such as shrinking natural resources, climate change, deforestation, biodiversity loss, food security, and the deterioration of the natural environment, are making people more aware of the importance of sustainability.At the corporate level, sustainability has been integrated into strategies for manufacturing companies due to the increasing legal, competitive and monetary pressures raised by these severe challenges and imposed by various stakeholders, including, for example, suppliers, investors and governmental authorities [1,2].The focus has shifted from producing goods with certain functionalities to providing the customer with material or intangible value [3].In line with this, product-service systems (PSS) has been introduced to deliver value to customers and fulfill their needs by providing an integrated bundle of product-service offering [4][5][6][7][8].
PSS has the potential to embrace sustainability, especially environmental sustainability due to the possibility of reducing overall resource consumption through better utilization and maintenance of resources and better adaptation to changing market conditions and customer needs [4].In the PSS context, multiple stakeholders with specific responsibilities and different knowledge requirements/strategies are integrated to create extended valuecreation networks [5] throughout the entire product life cycle (PLC), i.e., the beginning-oflife (BOL), middle-of-life (MOL), and end-of-life (EOL) phases [9], indicating a need for holistic knowledge exchange between R&D (designers), manufacturers, users, and even recyclers [10].The requirements to integrate diverse knowledge relating to economic, social, and environmental considerations across the entire PLC inherently make knowledge and its management even more crucial and challenging to companies in the PSS context [11].
Being identified as the key processes in knowledge management (KM), knowledge sharing (i.e., knowledge contribution) and knowledge reuse (i.e., knowledge seeking and reuse) are considered crucial in the PSS context as they can be used to overcome the rebound effects raised from the prolonged product life in PSS [12,13].With the requirements of constantly updating and enhancing the functionalities and performance of the product [12], how to reuse knowledge effectively and efficiently turns out to be even more important as it can help companies to avoid re-inventing the wheel where relevant knowledge or a solution already exists to maximum value from KM.Although research on PSS design, evaluation, and operation methods has been progressing well, there are only a limited number of studies concerning knowledge management practice in PSS operations [14].Especially from the PLC perspective, only limited research on knowledge reuse has been carried out.Those few exceptions have mainly focused on the BOL phase while paying limited attention to the MOL phase empirically [15,16].For those few studies of the MOL phase, the focuses were on one of the MOL sub-phases, e.g., use and support [13], and empirical studies on the other sub-phases in the MOL phase were scant in the PSS context [16].From the PSS providers' perspective, they must support their customers and ensure the usefulness of their products throughout the entire PLC.Therefore, further investigation of knowledge reuse in the MOL phase is valuable.In particular, comparing the similarities and differences of knowledge reuse in both BOL and MOL phases would enrich the PSS research and refine the knowledge management research.
In response to the discussion above, the objective of the current study is to investigate knowledge reuse in the PSS context from a PLC perspective, especially focusing on the BOL and MOL phases.Because external logistics could be fulfilled by the manufacturing firms and third-party logistics companies [17], both manufacturing and logistics companies were the targeted companies in this study.Therefore, the research questions addressed in this study are: What are the main knowledge requirements for PSS providers in different PLC phases?What are the knowledge reuse strategies/practices in that context?What are the influencing factors behind them?Are the answers to the abovementioned questions similar or different in different PLC phases?By answering these research questions, this study intends to provide a PLC perspective on the existing knowledge management theory in the context of PSS.Practically, we hope that companies, especially PSS providers, can better understand their knowledge reuse status quo and adjust their knowledge management strategies to keep competitive and sustainable development.
In Section 2, the study's theoretical background will be outlined.Section 3 will cover the selected research methods, data collection and analysis methods.The results of the study will be presented in Section 4. A detailed discussion, the study's theoretical contribution, and empirical implications will be presented in Section 5.The study will be concluded with further suggestions in Section 6.

PSS and the Benefits to Sustainability
The similarity and high quality of products in most markets limit the space to differentiate products; hence designing and manufacturing functional products is no longer the sole source of competitive advantage for a company [7].To be competitive, companies have to increase the added value of their offerings by providing integrated solutions to improve their position in the value chain [18].At the same time, manufacturing companies have experienced increasing legal, competitive and monetary pressure to use resources more effectively and sustainably [2].With the central concept of shifting the focus of traditional businesses based on the design, manufacturing and sale of physical products to a new business orientation that takes into account the functionalities and benefits delivered through the combination of products and services [19], PSS has been defined as "a system of products, services, supporting networks and infrastructures that are designed to be competitive, satisfy customer needs and have a lower environmental impact than traditional business models" ([6], p. 239).Due to the potential of PSS to generate ecological and economic benefits, studies focusing on PSS have become more prolific since the late 1990s [7,20,21].
Regarding sustainability, the benefits of PSS have been discussed extensively in different studies.Compared to traditional product offerings, PSS enables the shift to a more sustainable economy because it has the potential to reduce overall resource consumption and environmental impacts through better design of the product-service offering, better selection and utilization of the materials, better maintenance of the products, and more efficient recycling, remanufacturing and reuse of the products [4,6].As Tukker [7] concluded, PSS is one of the most effective instruments to move society toward a sustainable economy.
PSS research is progressing well as a research field spreading across various disciplines, research domains [7,21], and geographical areas [7].However, the number of empirical studies is limited [22].Therefore, it would be beneficial to have a better understanding of PSS practice so that the application of PSS and the benefits realized from PSS could be clearly identified.

Knowledge Management in PSS Context from PLC Perspective
In a continuum with data, information, and knowledge, data comprises the simple facts which can be structured to be information, while information becomes knowledge when it is interpreted, put into context, or has meaning added to it [23].In other words, knowledge is created from information and closely relates to a person's beliefs and commitments [24].Given the special focus area of this research, it will not deepen the discussion about the way knowledge is created.In the current study, we implicitly adopted Alavi and Leidner's [25] definition of knowledge, which is "a justified belief that increases the entity's capacity for taking effective action" ( [25], p. 109), and it takes into account the interpretation and contextualization of information [26].
In the PSS context, products are dealt with not only within the manufacturing company but also in a distributed, mobile, and collaborative environment beyond the company's boundaries throughout the PLC phases [15], where multiple stakeholders with certain responsibilities are integrated to create the extended value-creation networks [5].In accordance with PLC, these stakeholders perform their operations to handle matters such as design, production, usage, service, recycling, refurbishing and disposal [27].A key success factor when developing products for PSS is to design the product from a life-cycle perspective by considering all of the phases in the product's life cycle [8], indicating a need for holistic knowledge exchange between multiple stakeholders with different knowledge requirements/strategies [5].However, with the increasing complexity of products, processes, value creation networks and IT environments in the PSS context, managing all the information from the entire PLC has become challenging [28].
Although PSS is considered more sustainable for the company and for society, some drawbacks of PSS have been raised, such as the rebound effects from the prolonged product life in the use-oriented PSS [12].Compared with new products, reused products in the use-oriented PSS may be more harmful to the environment, which requires PSS providers to constantly update and enhance the functionalities and performance of the product to counteract the rebound effect [12].This is essentially the main objective of knowledge management, especially knowledge sharing and reuse, which is even more important in the PSS context than a traditional product offering company [13].
As an umbrella term, KM refers to any managerial processes and practice that focuses on effective and efficient means of leveraging knowledge resources to enhance performance and create a competitive advantage [25].Many discussions around KM have focused on how knowledge is transferred, shared, and used (reused) in the company, which broadly concerns the movement of knowledge, but with different emphasis, from different perspectives, and intertwined with each other [29,30].Generally, there are two parties involved in the KM process: the knowledge sender/contributor/producer, which refers to the roles of employees when they have the knowledge to share with others; and the knowledge recipient or potential consumer/user, which refers to the roles of employees when they try to seek and use knowledge from others [25,30].To make the knowledge movement successful, effective and efficient transmission channels, i.e., the mechanisms, are necessary [31].Knowledge sharing typically emphasizes the sender's contribution to knowledge (i.e., knowledge contribution) from a supplier's (sender's) perspective, while knowledge reuse focuses on the demand for knowledge from a consumer's (recipient's) perspective (i.e., knowledge-seeking and reuse), and knowledge transfer emphasizes the efficacy of the knowledge movement between a predetermined sender to the recipient (i.e., effective and efficient transfer) [29,30].
Considering the relationships and differences in knowledge sharing, knowledge reuse, and knowledge transfer, as well as the more crucial role of knowledge reuse in the PSS context, as we discussed in Section 1, this study will further explore knowledge reuse from the recipient's perspective, with the emphasize on the mechanism used.Combining and simplifying the knowledge reuse process proposed by Markus [32] and Majchrzak, Cooper and Neece [29], the working definition of knowledge reuse in this study is: Knowledge reuse is the process in which the recipient seeks and acquires knowledge from the sender, initiates the knowledge movement from the sender to the recipient and applies the knowledge received, where the focal actor is the knowledge recipient.Here, knowledge reuse focuses on sourcing and reusing knowledge within the sender-receiver relationship, i.e., sourcing and reusing knowledge from a different individual or group rather than reusing the recipient's own knowledge.
The success of knowledge transfer depends largely on the mechanisms used, as they provide opportunities to transfer documents or experienced personnel, as well as communicate with others or other units [33].Therefore, knowledge transfer in this study is defined as the knowledge movement from the sender to the recipient, where the focus is the transfer mechanism used to facilitate the knowledge movement.
Although the importance of knowledge reuse has been recognized, only a limited number of studies on knowledge reuse have been conducted in the PSS context, especially from a PLC perspective, and those few exceptions have mainly focused on knowledge reuse in the BOL phase with limited attention paid to the MOL phase empirically [15,16].MOL knowledge, especially in-service information, should be reused collectively to achieve greater value [13].

Influencing Factors of Knowledge Reuse
Knowledge reuse is often not a natural act [34].It is important to understand the influencing factors to enhance knowledge reuse in an organization.In a generic knowledge sharing and reuse model, the knowledge sender, the knowledge recipient, the transfer mechanism, the knowledge being transferred, and the context where the knowledge transfer takes place are the key elements [30].Taking this model into account and in line with the working definition of knowledge reuse and knowledge transfer in this study, the influencing factors are categorized into two sets.The first category includes factors related to the people who reuse the knowledge (i.e., the knowledge recipient), and the Motivation-Ability-Opportunity (MAO) framework will be used to summarize these factors [35].The second category includes factors influencing the selection of the mechanisms to transfer knowledge between the sender and recipient.The Technology Acceptance Model (TAM) will be used to explain this set of factors [36].

Factors Related to the People
In the MAO framework, motivation represents one's willingness to act, ability refers to one's skills or knowledge base related to the action, and opportunity refers to the environmental or contextual mechanisms which enable action [35].In the knowledge management context, the MAO framework is used to examine how to stimulate knowledge transfer in a more structural manner [35,37].To facilitate knowledge transfer, the actors should not only be motivated to engage in knowledge transfer and have the ability to transfer the knowledge but also need to have the opportunity to be involved in the knowledge transfer.
For instance, with regard to motivation, it has been found that trust and perceived usefulness motivate knowledge seeking, whereas the effort required can prohibit knowledge reuse [38].Although motivation may initiate the recipient's willingness to seek and use/reuse the knowledge, it is difficult to take action without the ability to do so.Absorptive capacity refers to the ability to recognize the value of the knowledge, acquire it, assimilate it, and apply it, which is highly determined by the prior related knowledge possessed by the recipient [39,40].With expertise and experience, i.e., both in-depth knowledge and a broader knowledge base, a higher absorptive capacity enables knowledge recipients to identify useful knowledge relating to their expertise and apply it more easily [41].This is especially true in the case of the reuse of knowledge through an electronic repository due to the required relevant background knowledge for the application of the new knowledge [42].As indicated by Szulanski [30], a lack of ability is more likely to impede knowledge reuse compared to a lack of motivation.
Motivation and ability are not enough to ensure efficient knowledge reuse, as opportunities are necessary for these processes [35].More available opportunities will enable more actions.For instance, a learning culture treats learning as an investment rather than a cost to the company so that knowledge is constantly used to improve the current situation, which promotes knowledge reuse [43].In addition to the organizational culture, more and better information and communications technology (ICT) tools can lead to more knowledge reuse opportunities by making the distribution of knowledge easier and improving the accessibility to the knowledge [25,44].Especially during the last decade, social media has become a trend that has shaped individuals' behavior of reuse thanks to its capability in terms of communication, collaboration, connectivity, completing and combining [45].The unique characteristics of social media can help to overcome traditional barriers to knowledge transfer [46] by providing a natural combination of codification (i.e., person-to-document) and personalization (i.e., person-to-person) knowledge management strategies and could enable more effective and efficient knowledge transfer between knowledge senders and the potential recipients [47,48].

Factors Influencing the Selection of the Mechanisms
To have a better understanding of knowledge reuse in the company, the mechanism selection is important because a sufficiently adequate adoption of the mechanism can facilitate knowledge reuse.First proposed by Davis [36], the Technology Acceptance Model (TAM) has been used in many studies to predict users' acceptance of information systems.In TAM, perceived usefulness and perceived ease of use are specified as two determinants of usage intentions, and usage intention may eventually lead to actual use.
Perceived usefulness refers to the degree to which people believe that using certain systems can improve their job performance, directly impacting technology adoption [36].In the context of knowledge reuse, the perceived usefulness of a knowledge transfer mechanism can be reflected in the perceived reach and richness of the mechanism.Richness refers to the amount and type of information a mechanism can transmit in a certain time interval [49].Reach describes the knowledge transfer mechanism's ability to overcome geographical, temporal and hierarchical barriers in the transfer of knowledge [50].The transfer mechanisms must be adjusted to the type of knowledge being transferred to make knowledge transfer effective [31].The use of information technology can facilitate the transfer of codified knowledge, whereas the transfer of tacit knowledge requires the usage of rich mechanisms, such as face-to-face communication [31] or the movement of personnel across an organization [33].
The perceived ease of use has been measured from different perspectives, including being easy-to-use, easy-to-learn, easy to become skillful, and flexible to interact with [51], which can be categorized into the physical or mental effort required, and how easy it is to learn a system.Using a mechanism that requires less physical and mental effort will be more likely to be accepted by the user.Similarly, a mechanism that is easier to learn will be more likely to be used.
Knowledge reuse can enhance mutual learning, promote best practices, reduce operational costs, and facilitate organizational innovation [32,52].However, it does not happen naturally [34], and it normally cannot be forced by managers [53].In the existing literature, only a few studies have systematically investigated the influencing factors concerning knowledge reuse [54], making it difficult to enhance knowledge reuse in the firm.This motivated the author to investigate the enablers and barriers to knowledge reuse in the current study.
In summary, to address the research gaps discussed above regarding knowledge management in the PSS context, including the limited empirical PSS studies, the lack of knowledge reuse studies in PSS from a PLC perspective, and the incomprehensive understanding of the influencing factors of knowledge reuse, the primary objective of this study is to increase the understanding of knowledge reuse in the PSS context from a PLC perspective.

Research Approach and Methodological Choices
Considering the research objective (i.e., to develop a further understanding of knowledge reuse practice/strategies in the PSS context from a PLC perspective), the existing fundamental theories (i.e., the lack of existing extensive literature on the phenomena), the nature of the research questions (i.e., in the forms of how, what, and why), and the subjective and context-dependent nature of knowledge reuse in the company, an explorative multiple case study methodology is employed in this study.Semi-structured interviews were conducted as the primary data collection method as they allow instant clarification of the terminology involved and circumvent misunderstandings [55].Furthermore, semistructured interviews allow further elaboration on relevant topics by introducing follow-up questions considered important by both the interviewer and interviewees [56] to achieve a rich understanding of the topic.In addition to the primary data collection, secondary data (e.g., press releases, company documentation and information from the company's websites, and other publicly available information on the studied companies' knowledge management practices) were used to enrich the data as well as achieve triangulation [57].
In order to obtain rich information, a purposeful sampling strategy was used to select key informants [58] by considering their relevance and familiarity with the research topic.All the informants were managers in the respective functional department and were knowledgeable about knowledge management practices in the department and the company.Multiple informants were selected in each manufacturing company so that information from one interviewee could be confirmed by other interviewees in the same company to increase the validity of the results [59].Before conducting the interview, the invitation was sent to the participants through email to outline the research objective and how the collected data would be used.Informed consent from each participant was obtained to fulfill the ethical research practice standards [60].In order to protect the confidentiality of the interviewees, only their job titles were included, and the identifiable details were excluded [61].
A total number of 29 face-to-face on-site interviews were conducted in seven manufacturing companies and four logistics companies in Beijing and Tianjin, China, between June and October 2018.A summary of the companies and participants is presented in Table 1.The manufacturing companies were in different industries (e.g., traditional printing, high-tech electronic measurement, biochemistry, etc.) and with different sizes.Except for the biochemistry company, which was medium-sized, all the other manufacturing companies were large [62].The logistics companies provided services to different industries, with relatively small sizes compared to the manufacturing companies.Only one of these was medium-sized, and all the others were small.Different PLC phases and sub-phases were represented by the relevant functional departments in the company, among which R&D, purchasing, and production were used to represent the beginning-of-life phase, and logistics, customer service, and sales were used to represent the middle-of-life phase.The duration of each interview was between 45 and 120 min.The focus of the interview guidelines was on the thematic questions raised from the literature review, covering topics related to knowledge management practices in the department and in the company.Questions about the type/sources of knowledge used, knowledge reuse practice and the influencing factors were asked during the interviews.All the interview data were digitally recorded with permission, except for interviews in two manufacturing companies, where filed notes were written down by the interviewer.The audio records were fully transcribed verbatim by the interviewer and checked for accuracy through repeated listening.In terms of data analysis, data from the 27 semi-structured interviews were analyzed using thematic coding and analysis methods [64] in the NVivo 12 software program.Two interviews from manufacturing companies, one with the chief information officer and the other with the chief executive officer, were not included in the final data analysis through NVivo.Rather, the data were used to confirm the interpretations of other interviews as well as serve as triangulation to enhance the study's credibility.The data were analyzed and reported based on predetermined themes from the literature [65].The initial nodes in NVivo were created according to the main themes from the research questions, including knowledge requirements, knowledge reuse practice, and the influencing factors.

Results
The data analysis results from the semi-structured interviews will be presented in this section, including the knowledge types required for each PLC sub-phase, the knowledge sourcing scope and mechanism used, and the influencing factors.

Knowledge Requirements in Different PLC Sub-Phases
Categorizing knowledge based on its functions or related discipline, expertise, process/procedure knowledge, product knowledge, production/manufacturing knowledge, supplier knowledge, customer knowledge, market knowledge, and industry knowledge are considered in the interview guideline [66].According to the interviewees, various types of knowledge were applied in different PLC sub-phases.Table 2 displays more detailed information.The reasons and focus for using different types of knowledge in different sub-phases, as well as some quotes from the interviewees, are summarized in Table 3.

Knowledge Reuse-Knowledge Sourcing Scope and Mechanism Used
From the recipient's perspective, the focus of the current study on knowledge reuse is on knowledge sourcing (i.e., seeking and acquiring knowledge from which sender) and the mechanism used.All the interviewees stated that knowledge reuse was necessary and integrated into daily work.Reusing knowledge is a way to accumulate experience and increase efficiency, thus contributing to the company's sustainable development.In order to maximize the value, knowledge will be integrated and applied in accordance with factors like the company's present status, the latest market dynamics, and the project situation.
Knowledge reuse is a principle in our company, and this is especially true for R&D.

(C2/P3)
The knowledge accumulated is experience and norms for the particular company.Even if in the same industry and there are so many universal things, each company still has its own unique characteristics, such as the different process requirements, etc.
(C1/P2) Table 4 presents the scope of knowledge sourcing and the mechanisms adopted.This part also contains a few pertinent quotes from the interviewees.
We hope we can have more direct communication with our original supplier, i.e., the raw material, rather than the agent of the raw materials.

(C7/P23)
The completed record of the previous R&D project will be very helpful for future project proposals and approvals.

Knowledge Reuse-Influencing Factors
The interviews revealed multiple background factors and viewpoints influencing knowledge reuse, including factors pertaining to people (i.e., who reuse the knowledge) and factors related to the selection of knowledge-sourcing mechanisms.The emphasis on the factors also reflects the context, i.e., the purpose of knowledge reuse from the interviewed experts' point of view.Listed below are a few quotes from the interviews describing the presented influencing factors.
The ability of the R&D personnel is very important to evaluate the value of external knowledge, such as from the internet, from the customer, and from the conference.
(C7/P23) When encountering a problem, we immediately analyze our own capabilities to determine whether to ask for help from outside. (C1/P2) The premise of effective knowledge reuse is that the employee must be of a sufficient caliber.Active learning is important.
The employee himself/herself has the ability to learn, is willing to learn, and is persistent is very important for active knowledge searching and usage.

(C8/P24)
We prefer to get the latest policy from the official website because it is accurate (not fake) Of course, we want to search within our department first because we know the possibility of finding the needed knowledge is higher.
(C10/P26) Unimportant issues will be resolved over the phone because it is quicker, i.e., call R&D to solve the problem.Important and key problems will be fed back to R&D through email.
(C6/P20) In case of unexpected, emergent problems that happen in production or R&D, telephone communication is a priority to solve the problem.If it is not urgent, management software will be used to communicate and solve the problem.
(C7/P21) When there are some technical problems that need to be solved, there will be communication between the different relevant departments and personnel within and outside the company, such as technology (R&D), procurement, production, suppliers, etc.It is efficient to solve the problem by using the knowledge acquired from others. (C1/P2)

Discussion
In line with the empirical results, the discussion in this section will begin with the knowledge requirements.Following that, knowledge reuse practices will be discussed in terms of knowledge sourcing scope and mechanism used as well as the influencing factors.Finally, the theoretical contribution and empirical implications of this study will be emphasized.

Knowledge Requirements in Different PLC Sub-Phases
The results show that expertise, process/procedure knowledge, and product knowledge were used by all PLC sub-phases but with different focuses.Even in the same sub-phase, the requirement for the same type of knowledge is different based on particular job positions and responsibilities.For instance, all sub-phases in MOL used customer knowledge but with different focuses.Logistics focuses on the requirements of customers regarding delivery time and modes, customer service focuses on the usage experience from the customers, and sales focus on the customers' requirement and expectation of the product performance.It must be underlined that R&D, the only sub-phase in BOL that employs this knowledge in the firms we interviewed, also values customer knowledge.In addition to paying attention to customer needs when developing products, R&D personnel considered customer feedback to improve the product and better serve customers.
Some knowledge was only used in the BOL phase, i.e., production knowledge and supplier knowledge.Industry knowledge was only used in the MOL phase, in particular logistics, because logistics professionals need to be aware of the product's industry standard to properly arrange the product's transportation.The utilization of process/procedure knowledge in all the PLC sub-phases interviewed indicates the significance of standardization and systemization of work, regardless of which PLC sub-phase is.In particular, standardization of work can ensure the quality of knowledge, which is essential for selecting the relevant knowledge when the quantity, heterogeneity and velocity of available knowledge are increasing [27].
Expertise and process/procedure knowledge were considered equally important in all PLC sub-phases.In contrast, other types of knowledge had varying importance in the different sub-phases.For instance, whereas people in customer service believed that customer knowledge was the most significant, those in the production thought that production knowledge was the most vital.Additionally, as the company's strategy evolved from being a manufacturer to being a PSS supplier, the value or importance of different types of knowledge also altered.This was emphasized by one of the interviewees, i.e., 'With the transition of the company from selling product to selling solution, the importance of different types of knowledge changed accordingly.The importance level changed from product knowledge first to customer knowledge first.(C6/P20)'.

Knowledge Reuse-Knowledge Sourcing Scope and Mechanism Used
Table 4 in the previous section provided insights regarding the scope of knowledge sourcing and the mechanisms adopted.In the BOL phase, the point that needs to be emphasized involves knowledge-sourcing patterns of R&D and purchasing.Both subphases ask the supplier for in-depth information, such as the supplier's innovation, because it can be used in their own R&D to speed up the process and make better material choices.Additionally, conferences and exhibitions were crucial sources of knowledge for R&D, but no other sub-phases addressed them.The emphasis in MOL should be on the knowledge souring of logistics.The most significant external knowledge source for them was the government or regulatory authority, while other sub-phases hardly ever used it.This was in line with the expertise required in logistics, i.e., policy-related knowledge.The crucial role of R&D was also revealed from the knowledge reuse pattern as all the sub-phases acquired and reused the knowledge from R&D.
With regard to knowledge transfer mechanisms, mentor was the one that was only used within the same sub-phase, and job rotation and social media were unique mechanisms in the logistics sub-phase.In addition, the person-to-person mechanism was preferred in all the sub-phases, even though a knowledge repository existed in all the studied companies.

Knowledge Reuse-Influencing Factors
Influencing factors related to people and mechanism selection were founded in the data analysis results.For people-related factors, motivation and ability are important to realize knowledge reuse.Ability was noted to be even more crucial than motivation.For instance, a source's credibility was a key concern in knowledge source selection, requiring that the person reusing the knowledge had sufficient ability to evaluate both the knowledge and the knowledge sources.
With regard to mechanism selection, the most influencing factors are the possibility of obtaining knowledge, the convenience of the mechanism, and the importance/urgency level of the task.When seeking knowledge for the purpose of reuse, the most influencing factor was the usefulness of the knowledge.

Theoretical Contribution and Empirical Implications
For theoretical contributions, this study firstly enriched the empirical PSS studies by investigating knowledge reuse practice in the PSS context, thus answering the call by Qu et al. [14] for research to seek empirical knowledge management practices in PSS operations.Conducting empirical case studies from the PSS provider's perspective and from the PLC perspective (that is, considering the BOL and MOL phases), this study uncovered the similarities and differences of knowledge reuse practice and the corresponding mechanisms in different PLC phases and subphases.
Secondly, this study extended the current knowledge management literature toward a more concrete, fine-grained understanding of knowledge reuse.Knowledge reuse is crucial in the PSS context as it can be used to overcome the rebound effects from the prolonged product life in PSS [12,13].By investigating knowledge reuse practices in different PLC phases and sub-phases, the current study examined knowledge reuse in the PSS context and focused it on specific aspects, i.e., from the knowledge recipient's perspective.Thus, this study clarifies the managerial implications of knowledge management in the PSS context.The standardization and systemization of work were found to be important in all PLC sub-phases to guarantee the quality of work, as process/procedure knowledge was required to be frequently used in all sub-phases.In addition, most of the extant studies have focused on the importance and usefulness of using MOL knowledge in the BOL phase for current product improvement and future new product design [67].However, the current study indicated that seeking and reusing knowledge from the BOL phase, especially from the R&D sub-phase, was a prevalent phenomenon in both the BOL and MOL phases to increase work efficiency.
Thirdly, this study enhanced the understanding of the influencing factors surrounding knowledge reuse by structuring them into people-related factors (i.e., summarized in the MAO framework) and mechanism-selection-related factors (i.e., explained by the TAM).For instance, with regard to people-related factors, this study found that knowledge reuse (especially knowledge seeking) was highly influenced by the recipient's absorptive capacity, which was consistent with the existing literature, i.e., [41].This impact was more significant for the personnel in R&D departments in the current research settings.In addition, the learning culture in the company was found to facilitate knowledge reuse, which was consistent with the literature [43].
With regard to the mechanism selection-related factors, both perceived usefulness and perceived ease of use were found to affect mechanism selection for knowledge reuse.For instance, mentor (with a high degree of richness) was used within each product life-cycle sub-phase to obtain in-depth knowledge, and social media (high reach) was popularly used in the MOL phase, especially in the logistics sub-phase because it was convenient and easy to use, as well as very fast.In addition, this study found that person-to-person mechanisms were still preferred in the company, especially in the R&D sub-phase, although a knowledge repository could be found in all the companies in this study.
Based on the empirical findings, several guidelines for practitioners, in particular PSS providers, were offered to facilitate better knowledge reuse and remain competitive.First, the unique knowledge requirements in each product life cycle (PLC) sub-phases should be clearly identified.For instance, except for expertise and process/procedure knowledge, which were equally important throughout the entire PLC, the importance of other types of knowledge was not the same in different PLC phases.More efficient knowledge reuse between the various PLC phases and sub-phases will only be possible with the correct understanding of the knowledge requirements between the sender and the recipient.
Secondly, a match should be made between the knowledge sourced and the knowledge transfer mechanism used, which is especially important for knowledge reuse.A variety of factors should be evaluated simultaneously, but priority must be made based on the unique context.The factors include knowledge and task characteristics, the convenience of the mechanism, the sender's credibility, the receiver's knowledge requirements, etc.For instance, if an urgent problem can be solved by cooperation between two parties, a phone call plus digital flow (in the digital systems) would be more convenient and economical.The mentor may be preferred if the matter is not urgent but focuses on in-depth and tacit knowledge transfer.Thirdly, creating a culture/mechanism to retain competent employees in the company is important.No matter how efficient knowledge reuse is in the company, it is still impossible to replicate a person's knowledge because of the tacit knowledge possessed.Therefore, competent people will be a crucial resource for the company.

Conclusions
Considering the lack of empirical studies, especially in terms of knowledge management studies in the PSS context, this study investigated knowledge reuse practices in different PLC phases (BOL and MOL) and subphases (R&D, purchasing, and production in the BOL phase and logistics, customer service, and sales in the MOL phase) from a PSS provider's perspective.Not only does it advance the fields of knowledge management and product-service systems research, but it also provides advice for practitioners, especially PSS providers, on how to promote knowledge reuse and keep competitiveness.
When interpreting the findings of this study, some limitations should be taken into account.First, the empirical data was collected from companies operating in China by interviewing the managers or senior staff in the department or the company.The influencing factors of knowledge reuse in one context may not be applicable to other contexts.However, this specific context can still provide fruitful insights as PSS-related research has been increasing in China in the past decades, i.e., [7].Nonetheless, extending this research to other countries could enhance the generalizability of the results.Therefore, conducting studies in other countries, especially in developed countries, will be meaningful to compare the results with those from the emerging economy.
Secondly, the companies interviewed in this study were from different industries but limited in number, making it difficult to compare the industries' differences.Although the focus of this study is knowledge reuse in different product life-cycle phases rather than in different industries, it must be admitted that the focus of knowledge reuse varies in different industries, which may have different influencing factors even in the same PLC phase.Therefore, further research extending the study into a particular industry and conducting interviews with several companies in that industry would enhance the credibility of the results.Additionally, extending the study to different industries to compare the results would enhance the generalizability of the findings.
Thirdly, due to time and resource constraints, only the BOL and MOL phases in the PLC were considered in this study, without any specific concern for the EOL phase.To realize ecological sustainability in PSS, the EOL phase is indispensable, and there should be different factors influencing knowledge reuse.For instance, the impact of government support policy is crucial in decision-making for companies in the EOL phase [68].
With increasing requirements for sustainability, it is thus meaningful and important to extend the current study into the EOL phase, thus investigating knowledge reuse throughout the entire PLC.It is believed that such findings could provide more guidelines to enhance knowledge reuse practices throughout the PLC.Finally, the current study did not specifically investigate knowledge creation, an important process in knowledge management.As a result, in addition to considering the supplier side, a more in-depth discussion of how knowledge is created, supported by concepts like interaction design, as well as a more in-depth discussion of the perspectives and needs of participants in the life cycle, such as the input from the owner/operator of the equipment, will contribute to deepening knowledge management research in the PSS context, especially with regard to knowledge creation.

(
C7/P22) We want to get more knowledge from R&D because we must prepare in advance.(C5/P17) As a person in purchasing department, I really hope more R&D staff will come to rotate here.Job rotation helps us to learn in-depth product knowledge.(C5/P16) Normally, we first search for knowledge through person-to-person channels, then try to search from the documents.(C5/P18)

Table 3 .
Reasons and focus for using different types of knowledge in PLC sub-phases.