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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>Journal of Web Semantics 56 (2019) 1-10. URL:
http://dx.doi.org/10.1016/j.websem.2018.06.003. doi:10.1016/j.websem.2018.06.003.
[15] G. Santipantakis</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="doi">10.5281/zenodo.16704863</article-id>
      <title-group>
        <article-title>Ontology for Extended Vessel Representation and Multimodal Data Integration</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Simon Burbach</string-name>
          <email>burbachs@hsu-hh.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Lennart Mackert</string-name>
          <email>lennart.mackert@hsu-hh.de</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Maria Maleshkova</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Maritime Ontology, Vessel Data Integration, Ontology Engineering, Semantic Interoperability, Multimodal Data</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Professorship of Data Engineering, Helmut Schmidt University</institution>
          ,
          <addr-line>Holstenhofweg 85, 22043 Hamburg</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2025</year>
      </pub-date>
      <volume>2343</volume>
      <fpage>2</fpage>
      <lpage>6</lpage>
      <abstract>
        <p>The maritime sector generates vast amounts of heterogeneous data due to dense global vessel trafic. This data ofers significant potential for improving operational eficiency and ensuring safety at sea. However, its efective use is hindered by a lack of semantic alignment between diverse information sources. To address this challenge, we present AISHIP, an ontology designed to unify and semantically enrich maritime data. AISHIP extends the existing VesselAI ontology by incorporating enhanced vessel characteristics, additional trajectory information, multimodal vessel representations, and a detailed conceptualization of propulsion systems. The primary objective of AISHIP is to serve as a semantic interface that facilitates the integration of heterogeneous maritime datasets, enabling consistent annotation, querying, and reasoning across systems.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        Maritime transportation plays a crucial role in global logistics, with approximately 80% of international
trade being transported by vessels navigating international waters at any given time [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. In addition
to that, the maritime domain is also used for passenger transport, military, and private trafic with
diferent kinds of vessels. This results in a substantial number and wide variety of vessels operating
simultaneously in both national and international waters [
        <xref ref-type="bibr" rid="ref2 ref3">2, 3</xref>
        ]. Nearly all sea trafic generates relevant
data via onboard sensor systems, as well as communication with other ships and land stations via
the automatic identification system (AIS) [
        <xref ref-type="bibr" rid="ref2 ref3 ref4">2, 3, 4</xref>
        ]. This data mostly represents information about the
ship itself (e.g., name, flag, vessel type), but also includes its position, speed, course, and other details
transmitted via very high frequency radio.
      </p>
      <p>
        All collected data constitutes a heterogeneous mass of information, typically existing as an
unstructured and unrelated collection. This lack of semantic alignment significantly hinders critical applications
such as anomaly detection, trajectory prediction, and fleet optimization from unleashing their full
potential, making a common semantic model necessary [
        <xref ref-type="bibr" rid="ref5 ref6">5, 6, 7, 8, 9</xref>
        ]. Such a model provides the shared
conceptual basis required to integrate heterogeneous datasets into a coherent framework. Without
https://www.hsu-hh.de/dataeng/en/team/maria-maleshkova/ (M. Maleshkova)
      </p>
      <p>CEUR
Workshop</p>
      <p>ISSN1613-0073
such a model, these tasks remain fragmented and prone to errors, as they must rely on data originating
from diverse and often incompatible sources to enable well-founded and informed decision-making
processes, which are essential to ensure human safety.</p>
      <p>
        To organize, relate, and integrate such data, ontologies are commonly employed [
        <xref ref-type="bibr" rid="ref5">5, 8</xref>
        ]. In the
maritime domain, ontologies allow information about ships and vessel trafic to be used for consistent
classification, grouping entities that share the same characteristics, even if expressed in diferent forms.
For example, diferent representations of ship characteristics can be standardized to fit into a predefined,
uniform ship description [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Furthermore, these also serve as the basis for semantic interoperability
across information systems, facilitating standardized communication and data exchange.
      </p>
      <p>
        The main contribution of this paper is the introduction of the AISHIP ontology that enables the unified
and detailed representation of vessels. Our work builds directly on the existing VesselAI ontology [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ], as
it is mostly centered around trajectories and basic vessel characteristics. We expand it with additional
concepts and relationships. By integrating information from heterogeneous data sources, this extended
model allows for a richer and more precise description of ship-related entities. AISHIP incorporates
additional features to improve vessel identification and detailed classifications of propulsion systems
(PSs) and engine configurations, as well as extended trajectory data.
      </p>
      <p>Through this contribution, we aim to support the development of interoperable, extensible systems for
maritime analytics and to foster collaboration through the use of a shared semantic foundation. In doing
so, we specifically address the overarching goal of enabling more efective integration and interpretation
of maritime data. The ontology not only enables semantic alignment across heterogeneous sources but
also provides the structural basis for advanced analytics, which particularly includes anomaly detection
and behavior analysis. By establishing consistent representations of ship characteristics, trajectories,
and contextual factors, the model lays the groundwork for identifying deviations from expected patterns
and supporting data-driven maritime decision-making. In addition, the ontology enables the analysis of
historical ship data, allowing researchers and practitioners to uncover long-term operational patterns
and trends.</p>
      <p>Our work specifically makes the following contributions:
• The AISHIP ontology that extends the VesselAI ontology with further vessel characteristics,
trajectory data, options for multi-modal vessel representation, and methods for modeling ship
PSs;
• 48 competency questions (CQs) divided into four categories that reflect questions of the real
world, which were used to direct the ontology development;
• An ontology evaluation that assesses domain coverage.</p>
      <p>The rest of the paper is structured as follows. First, Section 2 presents data models that are related to
our aim, and show potential for reuse and extension. Then, Section 3 discusses motivating use-cases
that can be supported by AISHIP. Afterwards, we describe the ontology development process, as well
as its core modules, together with some axiomatic restrictions (see Section 4). In Section 5, we present
the evaluation process to date and outline future directions for ontology validation. We conclude the
paper with a summary and present tasks for future work in Section 6.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Data Models</title>
      <p>
        Several established ontologies and data models are relevant for addressing the objectives of our work and
provide useful insights for the development process. One example of such an ontology is the VesselAI
ontology [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. The ontology was developed as part of the project ”VesselAI”, funded by the Horizon
2020 Framework Programme of the European Union [10]. The VesselAI ontology provides a structured
semantic model for maritime knowledge associated with vessel trajectories. The authors structured the
content in four main modules: 1) Trajectories of Moving Objects, 2) Vessel Characteristics, 3) Contextual
Information, and 4) Events and Weather Conditions. Trajectories consist of temporally annotated
trajectory parts, each representing the connection of single geographical positions taken from AIS
signals. Each trajectory part is annotated with a time stamp, travel-related data (e.g., speed and course
over ground), as well as events (e.g., anchoring) and weather conditions (e.g., heavy precipitation or
freezing rain). Weather conditions follow the code registry of the World Meteorological Organization1.
These annotations are important, as environmental conditions and events influence the vessel’s behavior
and operational patterns.
      </p>
      <p>Regions of interest, like ports, fishing areas, and environmentally protected areas, are also modeled.
They are essential for linking the activities of vessels to relevant zones at sea. This allows for further
analysis of vessel trafic, and compliance with protected areas is possible. These spatial concepts are
represented by the OGC GeoSPARQL standard2 [11]. GeoSPARQL enables the modeling of spatial
relationships (e.g., inside, intersects, within) and enables more advanced queries through SPARQL
endpoints. This integration facilitates interoperability with existing spatial datasets and ensures
compliance with widely accepted geospatial standards, which is critical for maritime data analytics and
decision-support applications.</p>
      <p>Another relevant data model is the Common Information Sharing Environment (CISE)3 [12]. CISE is
an interoperability framework promoted by the European Union to enable secure and standardized
information exchange among maritime authorities. CISE defines a common semantic structure for
sharing data about vessels, their activities, and related events across diferent systems and domains.
CISE provides a common structure for maritime data, which simplifies the integration of heterogeneous
information sources and improves interoperability. This supports better cross-border situational
awareness and strengthens maritime safety.</p>
      <p>The W3C Semantic Sensor Network (SSN) ontology and its core module Sensor, Observation, Sample,
Actuator (SOSA) provide a widely adopted standard for describing sensors and their observations [13, 14].
SSN/SOSA enables the modeling of sensors, representing their outputs in a semantically consistent
way. This allows the integration of heterogeneous data from diferent systems while considering
metadata. Standardized sensor descriptions are a necessity for tasks like anomaly detection and
predictive maintenance.</p>
      <p>Based on this review of related data models, VesselAI ofers the greatest potential for extension
in our use cases. Its detailed trajectory modeling provides a strong foundation for analyzing vessel
behavior. However, it lacks critical features that are essential for our objectives. While the VesselAI
ontology provides a solid foundation for modeling vessel trajectories, its scope is largely limited to
AIS-derived attributes. It does not capture the full range of ship identification features required for
comprehensive integration. Furthermore, it lacks the representation of aggregated values, which are
crucial for behavioral analysis.</p>
    </sec>
    <sec id="sec-3">
      <title>3. Motivation and Usage Scenarios</title>
      <p>
        In the maritime domain, a wide range of heterogeneous data sources, like AIS tracks4, technical ship
specifications, and registry databases, must be combined and analyzed to support decision-making
processes in logistics, fleet management, monitoring, and research. However, these datasets often lack
a unified semantic structure as they are available in diferent formats that are not compatible, which
limits interoperability, reuse, and automated reasoning [
        <xref ref-type="bibr" rid="ref5">5, 8, 15</xref>
        ].
      </p>
      <p>The AISHIP ontology addresses this challenge by providing a formalized and extensible conceptual
model for representing ships and their properties in a machine-interpretable way. It builds directly on
the VesselAI ontology, which was systematically extended to cover additional ship-related information,
relationships, and data dimensions. It enables the integration of static and dynamic data across diferent
systems and supports consistent annotation, querying, and interpretation of maritime information.
1http://codes.wmo.int/306/4678, accessed: 25.07.2025
2https://www.ogc.org/standards/geosparql/, accessed: 27.07.2025
3https://emsa.europa.eu/cise-documentation/cise-data-model-1.5.3/, accessed: 27.07.2025
4https://www.marinetraffic.com/, accessed: 01.08.2025</p>
      <p>By providing a unified representation of vessel-related information that includes static attributes
(e.g., dimensions, ownership, engine types), dynamic behavior (e.g., trajectory data), and
systemlevel components (e.g., propulsion), the ontology ofers a foundation for numerous use cases in both
commercial and operational maritime contexts.</p>
      <p>Through standardized identifiers (e.g., Maritime Mobile Service Identity – MMSI, hull identification
number – HIN), descriptive properties (e.g., ship type, dimensions, flag), and diverse data modalities
to represent ships (e.g., image, sonar signature, and textual description), ships can be uniquely and
consistently recognized, even when source systems difer. In addition, by formally linking ships with
their historical and planned trajectories, the ontology supports predictive analytics such as trajectory
forecasting, behavior pattern recognition, and route anomaly detection. This capability is particularly
valuable for risk management, monitoring, and real-time operational decision-making.</p>
      <p>The AISHIP ontology ofers a wide range of potential application scenarios across diferent areas
of the maritime domain. By providing a formal and semantically rich representation of vessels, their
components, and behaviors, the ontology supports tasks that rely on structured, interoperable, and
machine-readable maritime knowledge:</p>
      <p>Fleet Management and Operational Planning. In the domain of fleet management, the ontology
provides standardized and machine-readable descriptions of vessel characteristics, such as the ship type,
the associated PSs, the navigational status, and the past trajectories. This standardization supports better
integration of heterogeneous fleet data, enabling consistent comparison and classification of vessels
across diferent systems and operators. By relying on a common vocabulary and formal structure, the
ontology reduces ambiguity, improves data interoperability, and facilitates automated reasoning about
lfeet composition, readiness, and compliance. Furthermore, the integration of inferred and aggregated
behavioral data, like region-specific operational stays, adds a predictive and context-sensitive dimension.
As a result, operators can make more informed decisions when assigning ships to tasks, planning
maintenance schedules, or evaluating environmental and regulatory criteria across the fleet.</p>
      <p>Search and Rescue (SAR) Operations. In emergency situations, such as ship distress or
manoverboard events, time-critical information is essential. The ontology supports SAR missions by enabling
fast semantic querying of further relevant vessel trajectory data: estimated position and predicted
trajectory. It also helps to identify nearby vessels with suitable equipment or capacities for assistance
by analyzing predicted trajectories, improving coordination, and response times.</p>
      <p>Semantic Data Integration, Search and Analysis. The ontology acts as a common semantic layer
across disparate data systems, such as AIS feeds, ship registries, classification society databases, and
onboard monitoring platforms. This harmonization allows for federated querying, automated data
linking, and cross-system analysis using shared concepts and unified, controlled vocabularies.</p>
      <p>Digital Twins and Life Cycle Simulations. The ontology provides a structural backbone for
building digital twins of vessels by modeling the types of propulsion systems and their interconnections.
Formalizing the relationships between components such as engines and propellers establishes the
basic foundation for representing operational states and long-term performance characteristics. By
extending the modules with additional system components and state information in the future, they
support virtual testing, maintenance simulations, and system-level evaluations, thereby enabling more
comprehensive analyses over the vessel’s entire life cycle.</p>
    </sec>
    <sec id="sec-4">
      <title>4. Ontology Development</title>
      <p>For the development of our ontology, the SABIOx methodology [16] was chosen to guide the process.
The SABIOx methodology follows a five-phase life cycle comprising the requirement phase, setup phase,
capture phase, design phase, and implementation phase. In the requirement phase, the ontology’s purpose,
scope, and requirements are defined. The setup phase establishes modeling decisions such as language,
foundational ontology, and reuse strategy. During the capture phase, domain concepts and axioms are
identified and organized into a conceptual model, whereas the design phase focuses on modeling these
concepts into a coherent ontology schema. Finally, the implementation phase involves formalizing the
ontology in OWL. Throughout the entire process, interdisciplinary collaboration with experts from the
maritime domain was essential to ensure conceptual accuracy. CQs were defined at the beginning and
updated frequently to set the boundaries and contents of the ontology, guiding the development process.
Additionally, diverse knowledge and data sources were identified that needed to be represented in order
to make the ontology compatible with multimodal data.</p>
      <p>Based on the defined requirements, Ontology Design Patterns (ODPs) were identified and analyzed
to enable the reuse and extension of existing ontologies and their content. AISHIP incorporates
widely adopted ontologies and vocabularies such as QUDT, Schema.org, NEXIF, NFO, and NIE to
ensure semantic richness and interoperability. Following further principles of openness and reusability
promoted within the Semantic Web community, the AISHIP ontology is published under an open license,
accessible through a persistent URI, and archived on Zenodo with a DOI (10.5281/zenodo.16704863) to
guarantee long-term availability and proper citation.</p>
      <sec id="sec-4-1">
        <title>4.1. Core Modules</title>
        <p>ODPs serve as established best practices that address recurring issues in ontology development by
providing reusable modeling solutions. Their application improves the overall coherence and
interpretability of ontologies, promotes knowledge reuse, and simplifies the processes of integrating and
aligning heterogeneous models [17, 18].</p>
        <p>The main ontology that AISHIP (prefix ais) builds upon is the VesselAI ontology (prefix vai). While
VesselAI primarily focuses on ship trajectories, it provides a solid foundation for further extension. In
our work, this served as the starting point to integrate additional ship-related information relevant to
our specific use cases. AISHIP improves VesselAI’s standardized descriptions of vessels with five key
modules: Enhanced Vessel Characteristics, Enhanced Trajectory Data, Enhanced Contextual Information,
Motorization and Propulsion, and Multimodal Data Representation. They collectively add 73 classes, 38
object properties, and three data properties.</p>
        <p>1) Enhanced Vessel Characteristics. The first module (see Figure 1) extends the ontology with
ship-related information derived from AIS datasets. Based on these datasets, we identified attributes
that were not yet represented in VesselAI. These include the dimension specifications for the GPS
antenna placement, the ship owner, and the HIN.</p>
        <p>To improve behavioral analysis of vessels, modeling a ship’s typical location is essential. The property
ais:TypicalLocation is represented as an OGC Geometry (e.g., polygon) calculated over a given time
period. This way, AISHIP represents the expected location of a vessel. In addition, aggregated values
such as ais:hasAverageSpeedOverGround are relevant, as they correlate with the ship type.</p>
        <p>Another important enhancement introduced by AISHIP concerns datatype restrictions for both
dynamic and static AIS data. VesselAI initially allowed only the string datatype for measurements like
speed and course, as well as vessel dimensions, which is semantically inaccurate. To address this, we
integrated the QUDT (prefix qudt) ontology. Consequently, AISHIP models data properties such as
ais:hasSpeedOverGround, ais:hasHeading, and ais:hasGrossTn as object properties, pointing to
qudt:QuantityValue.</p>
        <p>2) Enhanced Trajectory Data. VesselAI primarily focuses on modeling vessel trajectories. To extend
this capability, we introduced additional dynamic and aggregated properties, like ais:hasDraught and
ais:hasAverageTrajectorySpeedOverGround. These attributes provide further insights into vessel
behavior, for example, by indicating activities like loading traded goods. In the context of behavioral
analysis, we also added a new subclass, ais:PredictedTrajectory, which specializes in representing
predicted vessel movements. This class is defined as a subclass of vai:SyntheticTrajectory. Figure
2 shows the relationships:</p>
        <p>3) Enhanced Contextual Information. The extension of contextual information adds another
subclass ais:RestrictedArea to vai:Place, since VesselAI does not provide the ability to model
restricted areas specifically. Restricted areas, according to our definition, can be regions where
access or navigation is limited due to security, safety, or legal regulations. It is distinguished from
vai:ProtectedArea, which represents areas of environmental constraints.</p>
        <p>4) Motorization and Propulsion. A major contribution of our work is the introduction of a module
that models ship PSs, which can be complex and composed of multiple main components (see Figure 3).
In this model, a ship is associated with a PS, where each PS can be classified according to its energy
source. Vessels most commonly feature a motorized PS (MPS). Others may rely solely on muscle power
(Muscle-powered propulsion system, MPPS), exclusively use wind for thrust (Pure wind propulsion
system, PWPS), or employ wind as assisted propulsion (Wind-assisted propulsion system, WAPS) to
support motorized propulsion. The latter is increasingly used in large cargo and tanker ships to reduce
fuel consumption and minimize environmental impact by carbonization [19].</p>
        <p>However, ais:PropulsionSystem only describes the concept of a PS, not the specific way
in which propulsion is generated. To capture this, we define an inverse property-pair that
links a PS to the class ais:PropulsionTechnology. Propulsion Technologies (PTs) actively
or passively generate thrust for the vessel. They are classified as well into the four main
types: ais:MusclePoweredPropulsionTechnology, ais:WindAssistedPropulsionTechnology,
ais:PureWindPropulsionTechnology, and ais:MotorizedPropulsionTechnology. The
categorization of PTs utilizing wind follows the International Maritime Organization (IMO) classification [ 19].
Our ontology therefore distinguishes between systems that are exclusively used in WAPS (e.g., Suction
Wings, Rotor Sails, Wind Assisting Soft Sails) and those designed for pure wind propulsion (e.g., Pure
Wind Soft Sail). In contrast, muscle-powered PTs (MPPTs) may include technologies such as paddles.</p>
        <p>Motorized PTs (MPTs) represent the more technically complex PTs and are further divided into two
subclasses: ais:JetPropulsor and ais:BladedPropulsor. Jet propulsors generate thrust through
high-pressure water or gas jets, a principle widely used in high-speed vessels [20, 21].</p>
        <p>MPTs are frequently exposed to cavitation. Cavitation is a phenomenon where vapor bubbles form
and collapse on propeller surfaces. They can cause erosion, which reduces eficiency. To mitigate
this, MPTs incorporate anti-cavitation mechanisms, which are currently modeled in a generic manner
without specialized subtypes.</p>
        <p>Among all PTs, bladed propulsors represent the most widely used systems in modern shipping. For
these systems, characteristics such as the number of blades and propeller diameter play a crucial role,
depending on the vessel type. Both of which are captured in our ontology.</p>
        <p>Bladed propulsors also vary in design and are adapted to specific ship types. Our model diferentiates
between older designs like the paddle wheel, specialized configurations such as the Voith Schneider
Propeller, and conventional screw propellers. The class ais:ScrewPropeller includes the most common
variants (e.g., fixed pitch propeller, controllable pitch propeller, and counter-rotating propeller) [ 20, 21].</p>
        <p>To represent how MPTs are powered, we modeled vai:Vessel as a subclass of schema:Vehicle, to
enable motorization details through schema:EngineSpecification. We introduced several subclasses
of engines. They are distinguished whether they have pistons or not, or if they represent a combination
of diferent engine types [ 22]. Examples include standard engines such as ais:DieselEngine and
ais:SteamTurbineEngine, as well as combined engine systems like CODOG (combination of
dieselengine or gas-turbine) and CONAS (combination of nuclear power and steam-turbine) [22].</p>
        <p>Finally, engines themselves are connected to an ais:PowerGenerationUnit, which provides the
necessary energy for propulsion (e.g., nuclear reactor, diesel combustion unit, solar array).</p>
        <p>5) Multimodal Data Representation. Ships can be described not only through AIS-related data but
also by leveraging additional sources of information. Common examples include visual representations
such as images, as well as textual descriptions that provide further context. Furthermore, ships exhibit
distinctive sonar signatures, which can be used to infer the vessel type (see Figure 4).</p>
        <p>To ensure accuracy, these multimodal representations must include metadata such as the capture date
and modification date, since ships may undergo structural or visual changes over time. For instance, a
hull repaint can make visual recognition unreliable. Similarly, sonar characteristics can change due to
modifications in the PS, hull shape, cargo load, or the application of insulation materials. To model
this metadata in a standardized way, we integrated concepts from the NEXIF, NFO, and NIE ontologies,
which provide established vocabularies for describing media properties, file information, and related
entities.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Restricting Data Types</title>
        <p>As already mentioned in the context of the module Enhanced Vessel Characteristics, we extended the
scope of how certain numerical values can be expressed. To achieve this, we specified the datatypes
of several data properties by creating new object properties following the same naming convention,
linking them to qudt:QuantityValue. This design allows QUDT’s mechanisms for unit annotation to be
applied, which significantly improves semantic interpretability. The newly introduced object properties
include ais:hasSpeedOverGround, ais:hasCourseOverGround, ais:hasHeading, ais:hasGrossTn,
ais:hasDeadweight, ais:hasLength, ais:hasWidth, ais:hasHeight, and ais:hasActualHeight.
The same modeling approach applies to all other properties we added that reference static or dynamic
numerical values that have units.</p>
        <p>This modeling strategy ofers several advantages. First, it ensures semantic correctness, as numerical
values are represented in a logically precise and standardized way. Furthermore, by using QUDT’s unit
vocabulary, ambiguity regarding measurement units is avoided, which facilitates consistent
interpretation of data across diferent sources. In addition, this approach enables reasoning over numerical
values, such as comparisons, and allows validation of value ranges through SHACL, for instance, when
checking if the course over ground lies within the range from 0° to 360°. Without this approach, only
string-based comparisons would have been possible, which are semantically weak and prone to errors.</p>
        <p>However, this decision also introduces a significant drawback, as the existing published datasets
of VesselAI need to be adapted accordingly to comply with the new object property definitions and
QUDT-based structure.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.3. T-Box Restrictions</title>
        <p>To ensure semantic consistency and avoid modeling redundancies, we introduce a set of T-Box
restrictions that govern class disjointness, property constraints, and domain-specific logical dependencies
between propulsion-related classes. These axioms provide a foundation for reasoning and validation in
our ontology.</p>
        <p>Class Disjointness. All subclasses of PS and all subclasses of PT are declared as pairwise disjoint.
This ensures that no individual can simultaneously belong to multiple sibling classes. This restriction
maintains a clear and unambiguous classification.</p>
        <p>Property Range Restrictions. Several properties are restricted to appropriate datatypes and
units. Since the properties refer to qudt:QuantityValue, the associated datatype and unit constraints
are applied through QUDT’s structure. For example: ais:hasDraught (type: decimal, unit: meters),
ais:hasSpeedOverGround (type: decimal, unit: knots), and ais:hasDiameter (type: decimal, unit:
centimeters). For navigational attributes such as ais:hasHeading and ais:hasCourseOverGround, we
enforce realistic value ranges from 0° to 360°, as values outside this range are not physically meaningful.</p>
        <p>Access Control Between Propulsion Systems and Propulsion Technologies. To prevent
inconsistencies and redundant object property definitions, we constrain the relationships between PSs
and PTs:
• Muscle-powered propulsion systems can only utilize muscle-powered propulsion technology.
• Motorized propulsion systems can only utilize motorized propulsion technology.
• Pure wind propulsion systems can only utilize pure wind propulsion technology.
• Wind-assisted propulsion systems can only utilize wind-assisted propulsion technology.
These constraints eliminate the need to redundantly model a separate direct object property for each
pair of subclasses, reducing complexity while preserving semantic precision.</p>
        <p>Exclusivity of Pure Wind Propulsion. Any vessel that employs a PWPS is restricted from having
any additional PS. This reflects the domain rule that vessels relying solely on wind propulsion cannot
combine it with other system types. The restriction represented as a logical expression:
∀ (( ∶ Vessel ∧ ∃ (propelledBy(,  ) ∧  ∶</p>
        <p>PWPS)) → ¬∃ (propelledBy(, ) ∧  ∶ P̸WPS))</p>
        <p>Incompatibility Between PWPS and Motorized or Wind-Assisted Systems. A stricter
consistency rule specifies that vessels equipped with an MPS or a WAPS must not include any PWPS.
This enforces the interpretation that wind assistance only supplements motorized propulsion, never
replacing it entirely. The restriction represented as a logical expression:
∀ ((∃ ( propelledBy(,  ) ∧ ( ∶</p>
        <p>MPS ∨  ∶ WAPS))) → ¬(∃ ( propelledBy(, ) ∧  ∶</p>
        <sec id="sec-4-3-1">
          <title>PWPS)))</title>
          <p>Wind-Assisted Propulsion Requires Motorization. A final consistency constraint ensures that
vessels equipped with WAPS must also include an MPS. This requirement reflects the semantic meaning
of “wind-assisted”: wind propulsion serves as a supplementary mechanism and not as the sole means
of propulsion. Without an MPS, a vessel would rely entirely on wind power, which contradicts the
intended definition of wind assistance. The restriction represented as a logical expression:
∀ ( ∶ VesselWithWAPS ↔ ( ∶ Vessel ∧ ∃ (propelledBy(,  ) ∧  ∶</p>
        </sec>
        <sec id="sec-4-3-2">
          <title>WAPS)))</title>
          <p>∀ ( ∶ VesselWithWAPS → ∃ (propelledBy(,  ) ∧  ∶
MPS))</p>
        </sec>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Evaluation</title>
      <p>The evaluation of the presented ontology was carried out in alignment with the SABIOx methodology,
applying a twofold strategy that combines verification and validation [ 16]. Verification aims to check
the internal consistency and correctness of the ontology, ensuring that its structure, classes, and
relationships have been implemented according to the specified design criteria and formal requirements.
In contrast, validation is concerned with assessing the usefulness of the ontology and its adequacy
in addressing real-world scenarios. It examines whether the ontology provides suficient power and
semantic clarity to support the intended application tasks efectively.</p>
      <sec id="sec-5-1">
        <title>5.1. Ontology Verification</title>
        <p>The requirements for the ontology are specified through a structured collection of CQs, which serve as a
foundational instrument for guiding and evaluating ontology development. These questions define the
types of information the ontology should be able to address and thereby help determine the essential
domain knowledge that must be explicitly represented within the model. The formulation of the CQs
was informed by three primary sources: the analysis of stakeholder requirements, the examination of
specific use cases relevant to maritime operations, and the structure and content of a representative
dataset on maritime vessels (e.g., AIS). This approach, out of multiple perspectives, ensures that both
theoretical coverage and practical applicability are adequately reflected in the ontology design. To
facilitate analysis and validation, the CQs were assigned to two categories. The first category comprises
general CQs, which aim to delineate the overall conceptual scope and boundaries of the ontology. These
questions help ensure that the model provides a coherent and comprehensive semantic framework for
representing vessel-related knowledge at a high level of abstraction. The second category includes use
case-specific CQs, which address concrete analytical challenges, such as predicting ship trajectories,
determining ownership distribution, identifying propulsion characteristics, or integrating multimodal
data sources for vessel representation.</p>
        <p>To systematically evaluate the final ontology with the defined CQs, we aligned each CQ to the
associated classes and properties it is modeled by. This way, it can be ensured that each CQ is represented
in the ontology. Furthermore, it provides a structured approach to support design decisions and allows
the integration of future extensions. Organized into general and use case-specific questions, Table 1
presents an excerpt of eight CQs, further divided according to the module to which they belong.</p>
        <p>After carefully mapping all CQs to the model, we can confidently confirm that the model achieves a
domain coverage of 100%. It demonstrates that the model is conceptually complete with respect to its
intended scope and capable of supporting all identified use cases.</p>
      </sec>
      <sec id="sec-5-2">
        <title>5.2. Ontology Validation</title>
        <p>To fully assess the ontology’s applicability and adequacy in real-world scenarios, it is essential to test
its behavior with representative data. The validation process of SABIOx involves creating a dataset of
individuals that covers the ontology and represents realistic entities. CQs are translated into SPARQL
queries and executed against this dataset. If the query results align with the expected answers, the
ontology can be considered to fulfill its intended purpose.</p>
        <p>Currently, such a dataset has not yet been created, but we outline the approach for its development.
We plan to adapt and extend the dataset published by the VesselAI authors [23]. This adaptation will
require datatype adjustments (as we restricted them) and a strict alignment with the modeling approach
based on QUDT.</p>
        <p>In addition, SHACL shapes will be defined based on the ontology’s axioms to validate whether the
dataset complies with the defined restrictions. For example, a shape will ensure that a vessel using rotor
sails for wind-assisted propulsion must also include an engine as the primary MPS. To complement
synthetic data, we plan to consult the maritime experts to incorporate real-world domain data into the
dataset. By following this strategy, we aim to ensure the ontology’s robustness and achieve a recall of
1.0 during query-based validation.</p>
      </sec>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusion and Future Work</title>
      <p>In this paper, we introduced AISHIP, an extension of the VesselAI ontology designed to enable a
more comprehensive and semantically consistent representation of vessels. Our work addresses key
limitations of VesselAI by incorporating additional vessel characteristics, enhanced trajectory modeling,
multimodal vessel descriptions, and a detailed conceptualization of PSs. These extensions close the
gap in semantic alignment between heterogeneous maritime data sources and resolve inaccuracies
related to the representation of numerical measurements and their units. By integrating recognized
standards such as QUDT, GeoSPARQL, and OWL-Time, AISHIP adheres to FAIR principles, ensuring
interoperability, reusability, and semantic precision across maritime information systems.</p>
      <p>Future work will focus on creating an extended dataset to validate the ontology through
SPARQLbased CQ testing and SHACL shape evaluation. Furthermore, we plan to assess the ontology in practical
scenarios, including trajectory prediction and SAR operations, to demonstrate its applicability in
realworld contexts. Another major direction involves linking AISHIP with SSN/SOSA to incorporate
sensor data, enabling advanced use cases such as estimating fuel consumption along specific routes.
These additions will broaden the applicability for maritime analytics, decision support, and operational
optimization use-cases.</p>
    </sec>
    <sec id="sec-7">
      <title>Declaration on Generative AI</title>
      <p>During the preparation of this work, the author used ChatGPT and Grammarly in order to: Grammar
and spelling check, translate, paraphrase, and reword. After using these tools, the author reviewed and
edited the content as needed and takes full responsibility for the publication’s content.</p>
    </sec>
    <sec id="sec-8">
      <title>Resource Availability Statement</title>
      <p>The AISHIP ontology5, the competency questions6 are available on GitHub [24] and Zenodo
(DOI: 10.5281/zenodo.16704863). All resources are licensed under Creative Commons
AttributionNonCommercial-ShareAlike 4.0 International.
5https://burbachs.github.io/AISHIPOntology/AISHIP.owl
6https://github.com/BurbachS/AISHIPOntology/blob/main/CQs/CompetencyQuestions.txt</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <source>[1] United Nations Conference on Trade and Development (UNCTAD)</source>
          ,
          <source>Review of Maritime Transport</source>
          <year>2024</year>
          : Navigating Maritime Chokepoints,
          <year>2024</year>
          . URL: https://unctad.org/publication/ review-maritime-transport-2024, accessed:
          <volume>01</volume>
          .
          <fpage>08</fpage>
          .
          <year>2025</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          [2]
          <string-name>
            <given-names>Z.</given-names>
            <surname>Wang</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Claramunt</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.</given-names>
            <surname>Wang</surname>
          </string-name>
          ,
          <article-title>Extracting Global Shipping Networks from Massive Historical Automatic Identification System Sensor Data: A Bottom-Up Approach</article-title>
          , Sensors
          <volume>19</volume>
          (
          <year>2019</year>
          )
          <article-title>3363</article-title>
          . URL: http://dx.doi.org/10.3390/s19153363. doi:
          <volume>10</volume>
          .3390/s19153363.
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          [3]
          <string-name>
            <given-names>Y.</given-names>
            <surname>Yang</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.</given-names>
            <surname>Liu</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            <surname>Li</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Z.</given-names>
            <surname>Zhang</surname>
          </string-name>
          , Y. Liu,
          <article-title>Harnessing the power of Machine learning for AIS DataDriven maritime Research: A comprehensive review</article-title>
          ,
          <source>Transportation Research Part E: Logistics and Transportation Review</source>
          <volume>183</volume>
          (
          <year>2024</year>
          )
          <article-title>103426</article-title>
          . URL: http://dx.doi.org/10.1016/j.tre.
          <year>2024</year>
          .
          <volume>103426</volume>
          . doi:
          <volume>10</volume>
          .1016/j.tre.
          <year>2024</year>
          .
          <volume>103426</volume>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          [4]
          <string-name>
            <given-names>International</given-names>
            <surname>Maritime</surname>
          </string-name>
          <article-title>Organization (IMO), AIS Transponders</article-title>
          , n.d. URL: https://www.imo.org/en/ OurWork/Safety/Pages/AIS.aspx, accessed:
          <volume>01</volume>
          .
          <fpage>08</fpage>
          .
          <year>2025</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          [5]
          <string-name>
            <given-names>G. M.</given-names>
            <surname>Santipantakis</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Doulkeridis</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G. A.</given-names>
            <surname>Vouros</surname>
          </string-name>
          ,
          <article-title>An Ontology for Representing and Querying Semantic Trajectories in the Maritime Domain</article-title>
          , Springer Nature Switzerland,
          <year>2023</year>
          , p.
          <fpage>224</fpage>
          -
          <lpage>237</lpage>
          . URL: http://dx.doi.org/10.1007/978-3-
          <fpage>031</fpage>
          -42914-9_
          <fpage>16</fpage>
          . doi:
          <volume>10</volume>
          .1007/978- 3-
          <fpage>031</fpage>
          - 42914- 9_
          <fpage>16</fpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          [6]
          <string-name>
            <given-names>C.</given-names>
            <surname>Claramunt</surname>
          </string-name>
          ,
          <string-name>
            <given-names>C.</given-names>
            <surname>Ray</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E.</given-names>
            <surname>Camossi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.-L.</given-names>
            <surname>Jousselme</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Hadzagic</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Gennady</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Andrienko</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Y.</given-names>
            <surname>Theodoridis</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            <surname>Vouros</surname>
          </string-name>
          , L. Salmon,
          <article-title>Maritime data integration and analysis: recent progress</article-title>
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>