Expanding IMO Compendium with NAVTEX Messages for Maritime Single Window

Abstract

The International Maritime Organization (IMO) introduced the Maritime Service Portfolio (MSP) and Maritime Single Window (MSW) to enhance the digitalization and efficiency of maritime transportation. While the MSP defines 16 maritime services focused on safety, security, efficiency, and environmental protection, the MSW provides a unified digital platform for submitting and processing information related to a ship’s operations. To support the implementation of MSW, the IMO Compendium provides standardized data sets and reference models to enable seamless information exchange across maritime systems. This paper proposes an expansion of the IMO Compendium to integrate the MSP’s maritime safety information service into the MSW environment. The study focuses on the integration of NAVTEX messages, a key source of navigational safety information, by identifying their key attributes and structuring them according to the IHO S-124 standard. A case study demonstrates the feasibility of the proposed data structure by transforming a sample NAVTEX message into the expanded IMO Compendium format and testing its transmission using an open-source MQTT library. This paper provides a structured methodology for integrating NAVTEX messages, effectively bridging legacy systems with modern digital infrastructures and facilitating enhanced interoperability in maritime operations. The proposed data structure will be presented to standardization bodies for further consideration, contributing to ongoing efforts to improve maritime operational efficiency and support digital transformation.

1. Introduction

The MSP and MSW are key concepts introduced by the IMO to advance the digitalization and efficiency of maritime transportation. The MSP defines 16 maritime services designed to enhance safety, security, efficiency, and environmental sustainability in maritime operations [1]. To support these services through a unified and seamless interface, MSW was proposed as a platform where all information related to a ship’s arrival, stay, and departure can be submitted and processed digitally [2].

To facilitate the implementation of MSW, the IMO developed the IMO Compendium, which provides standardized data sets and reference models for seamless data exchange [3]. The IMO Compendium currently focuses on MSP’s port support services, considered the most immediate priority. However, despite the mandatory implementation of MSW beginning in January 2024, there are no fully operational ports or products capable of supporting its services. To address this gap, several countries are actively updating IMO Compendium data sets to enable MSP services within the MSW environment.

This paper focuses on expanding the IMO Compendium to integrate MSP’s maritime safety information service into the MSW environment. To achieve this, the study begins by analyzing NAVTEX messages to identify their key attributes, which are crucial for structuring the data in alignment with the IMO Compendium. NAVTEX messages, being loosely structured, require the organization of these key attributes to ensure compatibility. The IHO S-124 standard, specifically designed for maritime safety information, is utilized as a reference to define the necessary data structure [4]. The proposed structure ensures that NAVTEX messages are integrated in compliance with the requirements of the IMO Compendium. A case study is conducted to evaluate the feasibility of the proposed data structure.

Integrating NAVTEX messages into the IMO Compendium facilitates the efficient and standardized delivery of maritime safety information services from shore to ships during operations. The received maritime safety information can then be utilized to support local route planning, thereby contributing to ongoing efforts to enhance the operational efficiency of maritime transportation. Furthermore, to support the realization of MSW, the proposed data structure in this paper will be presented to relevant standardization bodies as part of the active updates to the IMO Compendium data sets being undertaken by countries.

2. Background

2.1. Maritime Service Portfolio and Maritime Single Window

The MSP and MSW, introduced by the IMO, are fundamental concepts designed to advance the digitalization and efficiency of maritime transportation. The MSP defines 16 categories of maritime services, ranging from vessel traffic service and aids to navigation service to port support service, maritime safety information service, and search and rescue service [1]. These services collectively support maritime safety, security, efficiency, and environmental protection.

To support a unified and efficient delivery of MSP services, MSW was introduced. MSW is a digital environment that allows ships to electronically submit and process all necessary information required for port arrival, stay, and departure through a single interface [2]. The MSW acts as a centralized hub where ships can submit data electronically, either through user interfaces or system-to-system interfaces. Figure 1 illustrates the conceptual architecture of the MSW, showing how data flows between ship operators, agents, port authorities, and other relevant stakeholders.

The MSP and MSW work together to complement and enhance maritime transportation. While the MSP provides a standardized framework for maritime services, the MSW offers an efficient environment for processing and sharing these services through a unified digital interface. This collaboration reduces administrative overhead and operational costs while enabling real-time, data-driven operations, such as the Just-in-Time (JIT) concept, which optimizes port activities and minimizes delays. In maritime transportation, JIT refers to the ability of ships to arrive at ports precisely at the right time, allowing them to access port services without unnecessary delays or waiting periods. The JIT concept ensures that ships do not arrive too early, which would result in waiting before accessing the port, nor too late, which could disrupt schedules and delay cargo delivery. This optimization of arrival times helps reduce congestion, fuel consumption, and operational costs, while improving overall port efficiency.

2.2. IMO Compendium

To realize the MSW, the IMO Compendium provides essential data sets and reference models that support seamless data exchange among diverse maritime stakeholders [3]. The Compendium is a standardized framework developed by the IMO to harmonize data semantics and formats, facilitating the digital exchange of information required for ship arrival, stay, and departure. By ensuring consistency and interoperability across systems, the Compendium serves as a critical enabler for MSW and its associated services.

The IMO Compendium consists of two key components: the IMO Data Set, which defines the data elements required for operational and regulatory processes, and the IMO Reference Model, which establishes relationships between these data elements. These components are designed to align with international standards, such as those from the World Customs Organization (WCO) and the International Organization for Standardization (ISO), enabling uniform communication across global maritime systems.

The integration of the Compendium into port systems is supported through the IMO Facilitation (FAL) convention, which mandates the use of electronic data exchange for ship reporting formalities by January 2024. This system covers key declarations such as the General Declaration (FAL 1), Cargo Declaration (FAL 2), Crew List (FAL 5), and Passenger List (FAL 6). The Compendium also facilitates the exchange of critical data related to port logistics, environmental compliance, and security, including security-related information under the SOLAS regulations, notifications for waste delivery to port reception facilities, and reporting for ballast water management.

Currently, the IMO Compendium focuses primarily on data elements related to the port support service, a key component of the MSP. However, many nations are actively working to update the Compendium’s data sets to incorporate additional MSP services within the MSW framework [5]. As part of these efforts, this paper focuses on extending the IMO Compendium’s data set to support the maritime safety information service within the MSW environment.

2.3. Navigational Telex (NAVTEX) and Navigational Data (NAVDAT)

NAVTEX is a key component of the GMDSS, providing automatic broadcasts of maritime safety information such as navigational warnings, weather forecasts, and search and rescue updates. Operating in the medium-frequency (MF) band, NAVTEX uses 518 kHz for English broadcasts and 490 kHz or 4209.5 kHz for regional or other languages. With a range of up to 400 nautical miles, it ensures the timely delivery of crucial information to vessels, enhancing maritime safety and operational efficiency [6].

NAVTEX messages are categorized into specific types, each serving a critical role in maritime safety:

• Navigational Warnings (Type A): information about hazards to navigation, such as drifting objects, wrecks, or changes to navigational aids.
• Meteorological Warnings (Type B): forecasts and warnings for adverse weather conditions, such as storms or fog.
• Search and Rescue (SAR) Information (Type D): updates on ongoing rescue operations, including the location of vessels in distress.
• Safety-Related Information (Type E): alerts on marine pollution, piracy, or vessel-specific emergencies.

While NAVTEX remains a cornerstone of maritime safety, technological advancements have led to the development of a more advanced system, NAVDAT. Designed to complement or replace NAVTEX, NAVDAT addresses its limitations by supporting high-speed data transmission and multimedia content, such as images and graphical weather updates. Operating on 500 kHz and 2 MHz, NAVDAT enables faster and richer information exchange, aligning seamlessly with IMO’s e-Navigation strategy. Unlike NAVTEX, which is limited to text-based messages, NAVDAT supports real-time updates and a broader range of safety-critical data, improving decision-making and operational effectiveness.

However, NAVDAT, through an advanced system critical to the digitalization of maritime transportation, remains in its early stages of implementation. It has not yet been fully deployed globally and is currently operational in limited regions. Given this, and recognizing the active updates to the IMO Compendium’s data sets to support MSP services within the MSW environment, this paper focuses on NAVTEX as a practical and immediately applicable system for the maritime transportation industry.

2.4. IHO S-124 Standard

The IHO has introduced the S-124 standard to address the need for modernizing the dissemination of navigational warnings in the digital age. As a key component of the IHO’s broader S-100 Universal Hydrographic Data Model, the S-124 standard defines a harmonized data structure for delivering navigational safety information in digital formats [4]. These formats are fully compatible with modern systems such as electronic chart display and information systems (ECDIS), ensuring seamless integration into digital maritime operations and enhancing the overall efficiency of navigational communication.

The S-124 standard serves as a bridge between traditional and modern digital frameworks, addressing the need for efficient dissemination of navigational safety information. While NAVTEX uses predefined text-based formats transmitted over radio frequencies, S-124 defines the data structure required to transmit equivalent navigational warnings through digital channels. This approach aligns with IMO’s e-Navigation strategy, supporting the transition of legacy systems like NAVTEX into interoperable, modern platforms. By referencing S-124, navigational safety information can be restructured into a consistent and precise format, facilitating efficient dissemination across diverse digital systems.

A significant advantage of the S-124 standard lies in its utility for designing data structures for NAVTEX messages to be integrated into the IMO Compendium. NAVTEX messages, which traditionally follow basic data formats, lack the detailed data element structures required for inclusion in advanced digital systems. The S-124 standard provides a valuable reference for defining these structures, enabling NAVTEX data to be reformatted into machine-readable, harmonized formats. This adaptation supports the integration of NAVTEX messages into platforms such as the IMO Compendium and the MSW, both of which rely on standardized data for real-time exchange and enhanced operational efficiency in maritime transportation. This paper utilizes the S-124 standard as a critical reference for structuring NAVTEX messages in a way that aligns with the requirements of the IMO Compendium.

2.5. Literature Review

Recent research has extensively explored the integration of traditional maritime systems with modern digital frameworks to enhance efficiency, safety, and interoperability. The following studies are categorized into three key themes: MSW and data standardization, navigational safety and communication systems, and efficiency in maritime transport.

Studies focusing on MSW and data standardization highlight the critical role of MSW systems in streamlining administrative processes and improving operational efficiency at ports. Ogunlesi, C.D.C. [7] emphasizes the need to align MSW systems with the IMO Reference Data Model to ensure interoperability across borders. Similarly, Cauwer, N.D. et al. [8] discuss the IMO Reference Data Model as a key solution for harmonizing ship-port data exchanges, addressing challenges related to stakeholder collaboration and standardization. Hagaseth, M. et al. [9] propose an architectural framework for maritime intelligent transport systems, focusing on integrating international standards like UNECE and WCO to create cohesive and interoperable systems that enhance digitalization across ships and ports.

Research on navigational safety and communication systems explores advancements in systems that support maritime safety and communication. Uyà Juncadella, À. [10] investigates the evolution of vessel traffic services (VTS) toward e-navigation, advocating for a unified global VTS model integrated with emerging digital technologies to improve maritime safety and operational efficiency. Lee, C. and Lee, J. [11] analyze Bi-LSTM CRF models for the semantic classification of NAVTEX messages, demonstrating their potential to improve machine-readability and facilitate integration with systems such as ECDIS. Similarly, Akyol, A.E. and Keçeci, T. [12] examine NAVTEX messages in the Mediterranean region, identifying trends in navigational risks and emphasizing their importance in preventing maritime accidents.

Studies addressing efficiency in maritime transport focus on improving operational effectiveness and understanding the economic impact of maritime activities. Karamperidis, S. et al. [13] analyze the effect of LNG carrier port congestion on energy inflation in the euro area, showing that discharge delays directly impact natural gas prices and inflation. Wu, L. et al. [14] explore mapping global shipping density using AIS data, developing error-correction algorithms to generate high-resolution maps that support safety, logistics, and environmental monitoring. Rong, H. et al. [15] propose a data mining approach for maritime traffic characterization and anomaly detection, highlighting its effectiveness in monitoring ship behavior and ensuring safety. Li, H. et al. [16] evaluate machine learning and deep learning methods for ship trajectory prediction using AIS data, providing benchmarks for predictive modeling and supporting the development of autonomous navigation systems.

As digitalization progresses in maritime transportation, integrating traditional systems with modern frameworks becomes increasingly vital for ensuring safety, efficiency, and interoperability. Expanding the IMO Compendium with NAVTEX messages within the MSW framework is a significant step toward achieving these goals. By incorporating NAVTEX messages—an essential component of the GMDSS—into the IMO Compendium, this integration supports the standardization of maritime safety information. This effort aligns with ongoing advancements in digital maritime systems, facilitating seamless information exchange while enhancing navigational safety and operational efficiency across global maritime networks.

3. Extending the IMO Compendium with NAVTEX Messages

MSP defines and standardizes a range of maritime services to ensure consistent information exchange, and the MSW enables efficient processing of this information through a unified environment. To support the implementation of MSW, the IMO Compendium provides data sets and reference models that facilitate the seamless exchange of maritime-related information. Although the IMO Compendium currently focuses on data sets related to MSP’s port support services, this study aims to expand its scope by integrating the maritime safety information service into the MSW environment.

To achieve this, the integration of NAVTEX messages, which are essential for disseminating navigational safety information, is proposed. This process entails analyzing NAVTEX messages to identify key attributes and restructuring them in accordance with the requirements of the IMO Compendium. The IHO S-124 standard is employed as a reference to define the data structure necessary for this transformation, ensuring that the restructured NAVTEX messages align with international standards and are compatible with modern digital frameworks.

Integrating NAVTEX messages into the IMO Compendium necessitates a systematic approach to maintain data consistency and adherence to international standards. First, the essential attributes within NAVTEX messages are identified to facilitate their structured representation. These attributes are then mapped to the S-124 data model, which provides a standardized framework for organizing maritime safety information. Finally, the structured data is integrated into the IMO Reference Data Model.

3.1. Identifying Key Attributes of NAVTEX Messages

NAVTEX messages typically consist of identifiers, timestamps, and contents but the contents can be flexibly structured. To apply NAVTEX messages into the IMO Compendium, it is required to analyze contents to identify commonly transmitted information. An analysis of 1000 NAVTEX messages, collected between January and August 2024 in the Atlantic and Barents Sea regions, identified key attributes listed in

Table 1. Key attributes of NAVTEX messages.

NAVTEX Attribute	Description
Message type	Type of navigational warning or information, such as buoy status or exercises.
Transmission time	Time when the NAVTEX message was transmitted (UTC).
Message serial number	Unique identifier for the NAVTEX message (e.g., 370/23).
Source identifier	Identifier of the message originator or the station that sent the message.
Geographical area	The specific area mentioned in the message (e.g., Gulf of Finland).
Coordinates	Latitude and longitude of the reported hazard or event.
Validity period	Time period during which the message is valid or relevant.
Cancellation time	The time when the message is no longer valid (if applicable).
Event description	Detailed description of the event or hazard (e.g., “Light buoy unlit”).

[6,11]. Each attribute captures the crucial information required for safe maritime navigation, such as the type of navigational warning, transmission time, geographical information, and the event’s validity period.

3.2. Structuring NAVTEX Messages Using the S-124 Data Model

NAVTEX messages are not strictly structured, necessitating the organization of identified key attributes to integrate them into the IMO Compendium. The IHO S-124 standard is referenced to define the data structures required for this transformation. Once the key attributes of NAVTEX messages are identified, the next step involves structuring these attributes according to the S-124 data model. The S-124 standard is specifically designed for maritime safety information and ensures that navigational warnings are presented in a standardized format across multiple systems [4,17].

Table 2. Mapping NAVTEX message attributes to S-124 attributes.

NAVTEX Attribute	Matchable S-124 Attribute	Data Type	Remarks
Message type	warningType	Enumeration	Defined by S-124 product specification
	nAVWARNTitle	Text
Transmission time	publicationTime	Date Time	Expressed in UTC
Message serial number	warningIdentifier	Text	Expressed in maritime resource name
	warningNumber	Integer
Source identifier	agencyResponsibleForProduction	Text
Geographical area	locationName	Text
Coordinates	geometry	Point or Curve or Surface	List of geographical points
Validity period	dateTimeStart	Date Time	Expressed in UTC
	dateTimeEnd	Date Time
Cancellation time	cancellationDate	Date Time
Event description	navwarnTypeGeneral	Enumeration	Defined by S-124 product specification
	restriction	Enumeration
	information	Text

demonstrates how the NAVTEX message attributes are mapped to the corresponding S-124 attributes, ensuring compatibility and interoperability with the existing maritime data models. This mapping process is crucial for maintaining data consistency across platforms and ensuring that the information conforms to the IMO Compendium’s guidelines.

3.3. Integrating into the IMO Compendium

In integrating NAVTEX messages into the IMO Compendium, we followed the UML class diagram guidelines of the IMO Compendium. Figure 2 presents the UML diagram for the Navigational Warnings class, integrated into the IMO Compendium [2,3]. In this diagram, the class names are shown in red, and their attribute (data element) names are shown in green. This class is designed to support a one-to-many (0…*) relationship, which allows it to represent multiple warning messages within a single class instance. Each warning message contains essential attributes, such as the warning type, geographical area, and validity period, all mapped to relevant fields in the IMO Reference Data Model. Optional data elements follow the IMO Compendium conventions and are assigned a cardinality of (0…1) or (0…*) to reflect their flexible usage in message representation.

To explain the attributes of the Navigational Warnings class, we have prepared the data set description in

Table 3. Data set of navigational warnings integrated into the IMO Compendium.

Data Element	Format	Definition
WarningType	an..3	Type of the warning message.
WarningTitle	an..70	Title of the navigational warning.
PublicationDateTime	an..35	Date and time of the message’s transmission.
MessageSenderIdentifier	an..35	Unique identifier for the navigational warning message.
MessageReferenceNumber	n..8	Reference number assigned to the message.
ResponsibleAgencyName	an..70	Name of the agency responsible for issuing the message.
LocationDescriptionText	an..70	Description of the geographical area.
GeographicalCoordinates	n..11,3	List of geographical points (latitude, longitude).
ValidityStartDateTime	an..35	Starting date and time of the message’s validity.
ValidityEndDateTime	an..35	Ending date and time of the message’s validity.
CancellationDateTime	an..35	Time when the message is canceled.
WarningCategoryCode	an..3	General type of the warning.
RestrictionCode	an..3	Specific restrictions or warnings.
InformationDescriptionText	an..256	Additional textual information regarding the warning.

in accordance with the data elements specification guidelines [3]. Each data element’s format has been determined based on these guidelines. In the data format, “an” refers to alphanumeric characters, while “n” refers to numeric characters. For example, “a..3” signifies up to 3 alphabetic characters, and “n..11,3” means up to 11 numeric characters, with 3 positions reserved for a decimal.

Certain attributes, like WarningType, WarningCategoryCode, and RestrictionCode, require predefined code lists to ensure consistency across different systems and users. These code lists enable the standardized representation of common types of warnings, categories, and restrictions in maritime safety messages. Below, we present the respective code lists for these attributes.

The WarningType attribute uses a set of predefined codes that categorize the type of navigational warnings issued. These codes help maritime stakeholders quickly understand the scope and nature of the warning at a glance.

Table 4. Code list of WarningType.

Code	Code Name	Code Description
1	Local Navigational Warning	Navigational warnings for a localized area, such as a specific harbor, port, or inland waterway region.
2	Coastal Navigational Warning	Warnings for coastal waters, extending up to a few nautical miles offshore, addressing hazards in these areas.
3	Sub-Area Navigational Warning	Warnings for a specific sub-area within a broader NAVAREA, addressing hazards in a defined segment of the zone.
4	NAVAREA Navigational Warning	Warnings covering an entire NAVAREA, which is a large geographical region coordinated globally for safety.
5	NAVAREA No Warning	Indicates no navigational warnings are currently in effect for the entire NAVAREA.
6	Sub-Area No Warning	Indicates no active navigational warnings within a sub-area of a larger NAVAREA.
7	Coastal No Warning	Indicates no active navigational warnings for coastal waters.
8	Local No Warning	Indicates no active navigational warnings for a localized area, such as a harbor or inland waterway.
9	NAVAREA In-Force Bulletin	Bulletin indicating that some NAVAREA navigational warnings are still in force.
10	Sub-Area In-Force Bulletin	Bulletin indicating that some navigational warnings within a sub-area are still in force.
11	Coastal In-Force Bulletin	Bulletin indicating that some coastal navigational warnings are still in force.
12	Local In-Force Bulletin	Bulletin indicating that some local navigational warnings are still in force.

provides the code list for WarningType, explaining each code and its corresponding description [3,4,5,6].

The WarningCategoryCode attribute classifies navigational warnings into broader categories, such as changes to navigational aids, drifting hazards, or environmental phenomena. This classification helps standardize warnings across different regions, making it easier to understand the type of hazard or event being reported.

Table 5. Code list of WarningCategoryCode.

Code	Code Name	Code Description
1	Aids to Navigation Changes	Changes to aids to navigation systems, such as buoys or lighthouses
2	Aquaculture and Fishing Installations	Presence of aquaculture farms or fishing installations that may pose navigational hazards.
3	Drifting Hazards	Reports of objects or vessels adrift, posing hazards to navigation.
4	ECDIS Operating Anomalies including Official Data Issues	Anomalies or issues related to ECDIS or official navigational data.
5	Other Hazards	Warnings about miscellaneous hazards not classified under specific categories.
6	Health Advisories	Advisories concerning health-related issues, such as pandemics or medical warnings.
7	Ice Information	Information regarding ice conditions, including icebergs or pack ice.
8	In-Force Bulletin	Information bulletin of navigational warnings currently in force.
9	Dangerous Natural Phenomena	Warnings of natural hazards such as volcanic activity, seismic events, or tsunamis.
10	Newly Discovered Dangers	Newly identified navigational dangers, such as uncharted rocks or wrecks.
11	Offshore Infrastructure	Information about offshore installations like oil rigs, wind farms, or platforms.
12	Piracy or Robbery	Warnings related to piracy activities or robbery incidents at sea.
13	Communication or Broadcast Service Change	Changes to maritime communication or broadcast services, such as frequency shifts or outages.
14	Routing Change	Changes in the routing system, such as new recommended routes or traffic separation schemes.
15	Scientific Instruments Change	Notices about the deployment or removal of scientific equipment like buoys or sensors.
16	Security Requirement Change	Changes in security measures or advisories related to maritime security.
17	Special Operations	Warnings related to special maritime operations, such as military or research activities.
18	Towing Operations	Warnings about ongoing or planned towing operations that may affect navigation.
19	Works	Notifications of construction or maintenance works at sea or nearshore areas.
20	Rig List	Information about the location or movement of oil or gas rigs.

shows the code list for WarningCategoryCode along with descriptions of each category [3,4,5,6].

The RestrictionCode attribute specifies legal or operational restrictions associated with a particular navigational warning. This may include restrictions like prohibited entry, fishing limitations, or speed restrictions. These codes are critical for ensuring that mariners are aware of the specific limitations or prohibitions within certain areas.

Table 6. Code list of RestrictionCode.

Code	Code Name	Code Description
1	Anchoring Prohibited	Anchoring is completely prohibited in the area.
2	Anchoring Restricted	Anchoring is restricted, subject to specific conditions or limitations.
3	Fishing Prohibited	Fishing is not allowed in the area.
4	Fishing Restricted	Fishing is restricted based on specific conditions or limitations.
5	Trawling Prohibited	Trawling is completely prohibited in the area.
6	Trawling Restricted	Trawling is restricted and subject to certain conditions.
7	Entry Prohibited	Entry into the area is completely prohibited.
8	Entry Restricted	Entry is restricted and subject to specific permissions or conditions.
9	Dredging Prohibited	Dredging activities are prohibited in the area.
10	Dredging Restricted	Dredging is restricted and can only occur under certain conditions.
11	Diving Prohibited	Diving is prohibited in the area.
12	Diving Restricted	Diving is restricted based on certain limitations.
13	No Wake	A “No Wake” zone, prohibiting the creation of significant waves.
14	Area To Be Avoided	Vessels should avoid this area for navigational safety.
15	Construction Prohibited	Construction activities are prohibited in the area.
16	Discharging Prohibited	Discharging waste or other substances is prohibited.
17	Discharging Restricted	Discharging is allowed only under specific conditions.
18	Industrial or Mineral Exploration/Development Prohibited	Industrial or mineral exploration is prohibited in the area.
19	Industrial or Mineral Exploration/Development Restricted	Exploration or development is restricted and subject to conditions.
20	Drilling Prohibited	Drilling is completely prohibited.
21	Drilling Restricted	Drilling is restricted based on certain limitations.
22	Removal of Historical Artefacts Prohibited	The removal of historical artefacts is prohibited.
23	Cargo Transshipment (Lightening) Prohibited	Cargo transshipment or lightning is prohibited.
24	Dragging Prohibited	Dragging is prohibited in the area.
25	Stopping Prohibited	Stopping vessels is prohibited in the area.
26	Landing Prohibited	Landing on shore is prohibited in the area.
27	Speed Restricted	Speed is restricted to a certain limit in the area.
28	Overtaking Prohibited	Overtaking other vessels is prohibited.
29	Overtaking of Convoys by Convoys Prohibited	Overtaking one convoy by another convoy is prohibited.
30	Passing or Overtaking Prohibited	Passing or overtaking is prohibited in the area.
31	Berthing Prohibited	Berthing is prohibited in the area.
32	Berthing Restricted	Berthing is restricted under specific conditions.
33	Making Fast Prohibited	Making fast (securing a vessel to a fixed object) is prohibited.
34	Making Fast Restricted	Making fast is restricted and subject to conditions.
35	Turning Prohibited	Turning vessels is prohibited in the area.
36	Restricted Fairway Depth	The fairway has a restricted depth.
37	Restricted Fairway Width	The fairway has a restricted width.
38	Use of Spuds Prohibited	The use of spuds (anchors used to secure floating platforms) is prohibited.
39	Swimming Prohibited	Swimming is prohibited in the area.
40	SOx Emission Restricted	Sulphur Oxide (SOx) emissions are restricted in the area.
41	NOx Emission Restricted	Nitrogen Oxide (NOx) emissions are restricted in the area.

lists the restriction codes and provides descriptions for each [3,4,5,6].

4. Case Study

To simulate the transmission of navigational warnings, we prepared a NAVTEX message as shown in Figure 3. The message originates from Petersburg and is designated as NAV WARN 332/24. It announces ship exercises in the Eastern Gulf of Finland, scheduled to take place from 302100 UTC SEP to 052100 UTC OCT, marking the area temporarily dangerous to shipping. The specific coordinates of the exercise zone are provided, and the message is set to be canceled on 052200 UTC OCT.

This message was manually converted into the Navigational Warnings class of the IMO Compendium, following the structure outlined in Figure 3 and Table 3. The result of this conversion is shown in

Table 7. Navigational warnings for case study.

Data Element	Value	Remarks
WarningType	4	NAVAREA Navigational Warning.
WarningTitle	Ship exercises	Title of the event.
PublicationDateTime	281332 UTC SEP	Date and time from the NAVTEX message.
MessageSenderIdentifier	Petersburg	Source identifier.
MessageReferenceNumber	332/24	NAV. WARN. NO. 332/24.
ResponsibleAgencyName	Petersburg authorities	Name of the agency for issuing the message.
LocationDescriptionText	Eastern Gulf of Finland	General geographical area.
GeographicalCoordinates	60-00.5N 027-16.5E, 60-05.4N 027-34.0E, 59-53.0N 027-48.0E, 59-48.0N 027-31.0E	Coordinates from the message.
ValidityStartDateTime	302100 UTC SEP	Start time of the exercise.
ValidityEndDateTime	052100 UTC OCT	End time of the exercise.
CancellationDateTime	052200 UTC OCT	Time when the message will be canceled.
WarningCategoryCode	17	Special Operations (Ships Exercises)
RestrictionCode	7	Entry Prohibited (area temporarily dangerous).
InformationDescriptionText	Ships exercises in area temporarily dangerous to shipping	Additional event information

. Table 7 maps the contents of the NAVTEX message from Figure 3 into the appropriate fields of the IMO Compendium’s data model. Key elements, such as the warning type, geographical coordinates, and validity period, have been captured and structured according to the standards of the IMO Compendium.

The ISO 19847 standard for shipboard data servers and the ISO 19848 standard for data exchange are crucial in supporting the MSW and the IMO Compendium. These standards enable the seamless integration of real-time and non-real-time data exchange between shipboard systems and external systems. The shipboard data server provides three types of services: streaming, request-response, and file input/output [19,20].

In this case study, we focus on the streaming service, which is closely linked to the Message Queuing Telemetry Transport (MQTT) protocol. MQTT is a lightweight, widely used messaging protocol designed for real-time data transmission, particularly well-suited for time-series data exchange between shipboard systems and external systems. Figure 4 illustrates the MQTT communication mechanism, which operates on a publisher-broker-subscriber model. In this model, publishers send messages to the broker, and subscribers request the broker to receive messages on specific topics of interest.

In this scenario, as shown in Figure 5, we assume a system where navigational warnings are transmitted as a service. A service provider located onshore sends navigational warning messages via MQTT. The shipboard data server on the vessel acts as the broker, relaying these messages to onboard systems, such as the ECDIS. These systems receive the navigational warnings and use them to optimize route planning, ensuring the ship arrives at the port on time.

The hardware configurations for the experimental setup were as follows: the service provider and shipboard system operated on 12th Gen Intel^® Core™ i5-12500 CPUs with 8 GB of memory, running Microsoft Windows 11. The shipboard data server was equipped with an AMD Ryzen™ 9 5950X CPU, 64 GB of memory, and utilized Microsoft Windows 11. Data transmission between these systems was supported by an L4 Switch hub with a 1 Gbps bandwidth capability.

Since the MQTT protocol organizes data into a hierarchical structure of topics, navigational warnings were structured into topic-based messages following the ISO 19848 data exchange standards. Figure 6 illustrates the topic structure of these messages. The unique ship identifier, based on the IMO number—a unique serial number assigned by the IMO to identify ships—serves as the primary identifier for each ship’s data. Each data element within the navigational warnings, as defined by the IMO Compendium, is mapped to a corresponding topic.

To verify successful transmission of navigational warnings from the service provider to the shipboard system, we used the Eclipse Mosquitto 2.0.20 open-source MQTT message broker [21]. Several open-source MQTT libraries, such as Eclipse Mosquitto, HiveMQ Community Edition, and EMQX, are available for similar applications. Among these, Eclipse Mosquitto was selected for its lightweight design, ease of configuration, and compatibility with various operating systems. The experiment followed these steps:

• The shipboard data server started the MQTT broker to handle the message transmission.
• The shipboard system subscribed to the NavigationalWarnings topic, awaiting incoming navigational warnings.
• The service provider transmitted the NavigationalWarnings topic with the message data.

Table 8. Service provider transmitting the navigational warnings message.

Command	Description
mosquitto_pub-t IMO123456/NavigationalWarnings/WarningType-m “4”-h 172.27.0.100	Publishes the warning type as “4” to the specified topic.
mosquitto_pub-t IMO123456/NavigationalWarnings/WarningTitle-m “Ship exercises”-h 172.27.0.100	Sets the warning title as “Ship exercises”.
mosquitto_pub-t IMO123456/NavigationalWarnings/PublicationDateTime-m “281332 UTC SEP”-h 172.27.0.100	Publishes the warning’s publication date and time.
mosquitto_pub-t IMO123456/NavigationalWarnings/MessageSenderIdentifier-m “Petersburg”-h 172.27.0.100	Specifies the message sender identifier as “Petersburg”.
mosquitto_pub-t IMO123456/NavigationalWarnings/MessageReferenceNumber-m “332/24”-h 172.27.0.100	Publishes the message reference number.
mosquitto_pub-t IMO123456/NavigationalWarnings/ResponsibleAgencyName-m “Petersburg authorities”-h 172.27.0.100	Sets the responsible agency name.
mosquitto_pub-t IMO123456/NavigationalWarnings/LocationDescriptionText-m “Eastern Gulf of Finland”-h 172.27.0.100	Provides a location description.
mosquitto_pub-t IMO123456/NavigationalWarnings/GeographicalCoordinates-m “60-00.5N 027-16.5E, 60-05.4N 027-34.0E, 59-53.0N 027-48.0E, 59-48.0N 027-31.0E”-h 172.27.0.100	Publishes geographical coordinates.
mosquitto_pub-t IMO123456/NavigationalWarnings/ValidityStartDateTime-m “302100 UTC SEP”-h 172.27.0.100	Specifies the warning’s validity start time.
mosquitto_pub-t IMO123456/NavigationalWarnings/ValidityEndDateTime-m “052100 UTC OCT”-h 172.27.0.100	Sets the validity end time for the warning.
mosquitto_pub-t IMO123456/NavigationalWarnings/CancellationDateTime-m “052200 UTC OCT”-h 172.27.0.100	Publishes the cancellation date and time.
mosquitto_pub-t IMO123456/NavigationalWarnings/WarningCategoryCode-m “17”-h 172.27.0.100	Sets the warning category code as “17”.
mosquitto_pub-t IMO123456/NavigationalWarnings/RestrictionCode-m “7”-h 172.27.0.100	Publishes the restriction code as “7”.
mosquitto_pub-t IMO123456/NavigationalWarnings/InformationDescriptionText-m “Ships exercises in area temporarily dangerous to shipping”-h 172.27.0.100	Provides additional descriptive information for the warning.

presents the results of the message transmission from the service provider. In this case, the ship ID was set to a fictional IMO number, IMO123456, following the topic structure outlined in Figure 6 and the values detailed in Table 7. Each topic, representing a key navigational warning data element, was successfully transmitted with the appropriate values, including the warning type, geographical area, and event details.

On the receiving end,

Table 9. Shipboard system receiving the navigational warnings message.

Received Data	Description
4	Warning Type: Indicates the type of navigational warning.
Ship exercises	Warning Title: Describes the nature of the warning.
281332 UTC SEP	Publication DateTime: Specifies when the warning was published.
Petersburg	Message Sender Identifier: Identifies the sender of the message.
332/24	Message Reference Number: Unique reference for the navigational warning.
Petersburg authorities	Responsible Agency Name: Agency responsible for issuing the warning.
Eastern Gulf of Finland	Location Description Text: Describes the area affected by the warning.
60-00.5N 027-16.5E, 60-05.4N 027-34.0E, 59-53.0N 027-48.0E, 59-48.0N 027-31.0E	Geographical Coordinates: Specifies the exact area of concern.
302100 UTC SEP	Validity Start DateTime: Start time of the warning validity.
052100 UTC OCT	Validity End DateTime: End time of the warning validity.
052200 UTC OCT	Cancellation DateTime: Indicates when the warning is canceled.
17	Warning Category Code: Specifies the warning’s category.
7	Restriction Code: Indicates the restrictions associated with the warning.
Ships exercises in area temporarily dangerous to shipping	Information Description Text: Additional details about the warning.

shows the result of the shipboard system received the transmitted navigational warnings message. To capture all the sub-topics under the navigational warnings, the shipboard system subscribed using the ‘#’ wildcard, which allows for subscribing to all sub-topics within a hierarchy. The table shows the received message, confirming that each topic, including coordinates, message type, and validity period, was successfully captured from the service provider.

The successful transmission and reception of the message, as demonstrated in Table 8 and Table 9, confirm that all key data elements—such as geographical coordinates, message types, and validity periods—were correctly sent and received by the respective systems.

5. Limitations and Discussion

This paper proposes a structured approach for integrating NAVTEX messages into the IMO Compendium, contributing to the modernization of maritime communication. However, it also presents certain limitations that need to be addressed in future work.

One key limitation lies in the scope of this study, which focuses solely on NAVTEX messages. As next-generation messaging systems like NAVDAT emerge, research into designing data structures for NAVDAT integration with the IMO Compendium will become necessary. NAVDAT, with its support for multimedia content and higher data transmission rates, will require tailored data structures that align with both the IMO Compendium and advanced communication protocols.

Additionally, while the proposed data structure supports the integration of NAVTEX messages, ensuring its applicability to the JIT concept in maritime transportation requires further validation. Future work should include experimental testing with real-world data and systems to evaluate metrics such as data transfer success rates and latency. These validations will determine whether the integration framework effectively supports JIT operations, such as optimizing port arrival times and reducing unnecessary delays.

Furthermore, the unstructured nature of NAVTEX content presents challenges in identifying and categorizing key attributes. Leveraging artificial intelligence (AI) techniques, such as natural language processing (NLP) and machine learning, is essential to automate and improve this process. We are actively conducting research in this area, and these efforts will be closely linked to the findings of this paper.

Additionally, this study does not extensively address the security aspects of maritime data exchange. While the proposed structure aligns with existing standards, implementing secure communication protocols and encryption methods is crucial to protect sensitive navigational data. Future research should explore robust encryption techniques and secure transmission methods to ensure data privacy and integrity within the MSW environment.

6. Conclusions

The MSP establishes a standardized framework for maritime services to ensure consistent and reliable information exchange, while the MSW provides a unified environment for efficiently processing this information. To support MSW implementation, the IMO Compendium offers standardized data sets and reference models that enable seamless data exchange across maritime systems.

This paper contributes to these efforts by proposing an extension of the IMO Compendium to incorporate MSP’s maritime safety information service into the MSW environment. The integration process involved analyzing NAVTEX messages to identify key attributes. These attributes were structured using the IHO S-124 standard, which provides a harmonized data model for maritime safety information, ensuring alignment with the IMO Compendium’s requirements and international standards. In the case study, a sample NAVTEX message was transformed into the proposed data structure and tested for data transmission and reception using an open-source MQTT library.

The case study validated the feasibility of the proposed data structure, through certain limitations require further investigation. While the integration of NAVTEX messages lays a practical foundation, the framework’s applicability to the JIT concept in maritime transportation requires additional testing. Future research should include experiments with real-world systems and data to evaluate performance metrics, such as transmission reliability, data latency, and system scalability. Moreover, the focus on NAVTEX does not fully address the demands of emerging systems like NAVDAT, which will require new data structures to accommodate advanced functionalities such as multimedia content and real-time updates. The unstructured nature of NAVTEX content also presents challenges for automation, highlighting the need for AI techniques for semantic analysis and message classification. Additionally, security concerns such as encryption and secure data exchange protocols must be addressed to ensure safe and reliable information transfer in the MSW environment.

Despite these challenges, the integration of NAVTEX messages into the IMO Compendium represents a significant step toward modernizing maritime safety information services. By enabling the seamless delivery of navigational safety information from shore to ships, this work supports local route planning and contributes to the goal of enhancing the operational efficiency of maritime transportation.

Finally, this study aligns with ongoing global efforts to update the IMO Compendium’s data sets, which are being actively pursued by various countries to advance MSP services within the MSW framework. The proposed data structure will be presented to relevant standardization bodies as part of these efforts and will undergo further verification through practical applications, contributing to the realization of a fully digitalized and interoperable maritime ecosystem.