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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A Modular Ontology Stack for Integrating OpenBIM and Bayesian Structural Health Monitoring and Prediction</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Cedric Driesen</string-name>
          <email>cedric.driesen@buildwise.be</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>LDAC 2025: 13th Linked Data in Architecture and Construction Workshop</institution>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2025</year>
      </pub-date>
      <fpage>25</fpage>
      <lpage>38</lpage>
      <abstract>
        <p>The Architecture, Engineering, and Construction (AEC) industry faces persistent challenges in integrating heterogeneous data for structural health monitoring (SHM) and facility management, specifically in capturing time-dependent degradation, probabilistic models reflecting uncertainty, and damage semantics. This paper proposes a Linked Data framework that extends Industry Foundation Classes (IFC) with semantic web technologies to address these gaps. By converting IFC data into a Resource Description Framework (RDF) graph via modular ontologies-including BOT, SOSA/SSN, OPM, DOT, and a custom LifeMACS Ontology (LFM)-the framework enables rich semantic queries, provides inputs for probabilistic analyses, and cross-domain interoperability. A Python-based conversion pipeline automates the translation of IFC geometry, sensor data, and inspection records into an RDF knowledge graph, while SPARQL queries demonstrate advanced capabilities, such as probabilistic crack-length or sensor value assessments and realtime data integration. A case study on a deteriorating reinforced concrete bridge validates the approach, showcasing its potential for improved statistical parsing directly using the RDF graph. Results highlight the framework's potential to connect static infrastructure data with dynamic lifecycle parameters. The work highlights the potential of semantic web technologies in advancing digital twin capabilities for the AEC industry.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Linked Data</kwd>
        <kwd>Structural Health</kwd>
        <kwd>Bayesian Modelling</kwd>
        <kwd>Probabilistic Modelling</kwd>
        <kwd>OpenBIM</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>The Architecture, Engineering, and Construction (AEC) industry increasingly relies on digital
technologies like Building Information Modelling (BIM) to address the complexities of designing,
building, and maintaining infrastructure [1, 2]. OpenBIM—particularly through the Industry
Foundation Classes (IFC)—has emerged as a prominent standard for exchanging building and
infrastructure information, helping to alleviate the persistent issue of data silos [3]. While direct
export from BIM authoring tools to Resource Description Framework (RDF) is possible, leveraging the
IFC standard allows the framework to integrate with diverse existing workflows and tools without
requiring specific adapters, despite potential information losses inherent in the format conversion
from native to IFC. However, despite IFC’s widespread adoption, significant challenges remain in
capturing rich semantics, facilitating advanced queries, and enabling flexible data linking across
heterogeneous sources, especially over a structure’s entire life cycle [4].</p>
      <p>A range of research efforts has explored ways to augment IFC with semantic web technologies.
While direct IFC-to-LBD conversions using schemas like ifcOWL exist [5], integrating domain-specific
semantics for SHM often requires mapping to broader Linked Building Data (LBD) ontologies [6–9].
Nonetheless, many existing solutions still struggle with more specialized requirements, such as
damage representation [10], time-dependent degradation [8], and probabilistic models [11], which are
increasingly relevant for structural health monitoring (SHM) applications [12].</p>
      <p>This situation becomes especially pressing in the context of facility management, where efficient
data integration and reliable interoperability play critical roles. Monitoring concrete structures, for
instance, requires aggregating inspection results, sensor measurements, and predictive simulation
data—often from multiple specialized tools—while also managing time- and context-sensitive
information, such as evolving damage or degradation along with associated uncertainties [12].
Conventional IFC-centric workflows provide robust geometry and basic semantic capabilities but can
fall short in representing richer relationships, intricate damage modelling [13, 14], and real-time
sensor data stream support [15].</p>
      <p>Against this backdrop, Semantic Web Technologies (SWT) and Linked Data (LD) approaches offer
an appealing solution to extend traditional BIM data with graph-based models and ontologies. By
converting IFC data to RDF and integrating domain-specific ontologies, stakeholders can use more
expressive queries, advanced reasoning, and seamless linking to external knowledge bases. Prior
research in this space has demonstrated the potential for IFC-to-LBD conversion to address
interoperability gaps [4, 6, 16, 17], but few solutions provide a comprehensive methodology spanning
standard ontologies that also includes custom damage and domain concepts.</p>
      <p>The LifeMACS (life-cycle methodology for the assessment of existing concrete structures) project
aims, among other things, to address these challenges by developing a comprehensive framework to
aid decision-making in facility management and structural health monitoring [12, 18]. By integrating
data from inspections and sensor measurements, the project enables a deep understanding of a
structure's performance using Bayesian material degradation and damage evolution models [18], as
well as Finite Element (FE) models for structural performance and temporal degradation prediction
[19]. These models lead to performance-based optimization of preventive as well as predictive
maintenance strategies [20]. The project involves a multidisciplinary team of researchers and industry
partners, ensuring the development of a robust, complete, and practical solution.</p>
      <p>In this paper, a Linked Data framework is presented that complements existing IFC workflows by
incorporating explicit semantic modeling of structural damage, sensor measurements, and other
lifecycle parameters—aligned with the needs of LifeMACS. Our approach extends and integrates standard
ontologies (BOT [7], SSN/SOSA [21], OPM [8], OMG/FOG [22, 23] or GeoSPARQL [24], OWL-Time,
DOT [10]) as well as introduce new concepts in the custom LifeMACS Ontology (LFM). By illustrating
the method through a reinforced concrete bridge case study, we show how IFC-to-LBD translation
simplifies complex data exchange while enabling deeper statistical analyses for predictive
maintenance and asset management. IFC-to-LBD approaches already exist [5, 25], but are out of the
box not aligned to the custom ontologies in the project, thus a custom solution was created. Ultimately,
this paper contributes a novel, ontology-driven methodology for harnessing Bayesian modeling based
on digital building models, reinforcing the broader role of Linked Data and other SWT in the LCM
phase of construction.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Methodology</title>
      <sec id="sec-2-1">
        <title>2.1. Overall Architecture</title>
        <p>The proposed data integration framework adopts a layered architecture designed to transform IFC
files into an RDF representation, while accommodating domain-specific extensions required for
structural health monitoring and facility management. Figure 1 illustrates the conversion workflow
which includes: (1) the IFC data ingestion and processing module, (2) the semantic mapping and
ontology alignment steps, and (3) the linked data and query interface. This structure ensures that
geometric and semantic information from IFC is retained, processed into specialized ontological
constructs, and made available for analysis or integration with external data sources.</p>
        <p>In the first step, IFC files are collected from existing BIM-based workflows. Then the parser
identifies relevant IFC entities (e.g., IfcWall, IfcBeam, IfcSlab, IfcSensor…), extracts the required
attributes, and prepares them for conversion. If necessary, partial geometry processing could be
performed to determine high-level spatial information, such as element boundaries or positioning, by
using for example the GeoSPARQL [24] or OMG/FOG ontologies [22, 23, 26].</p>
        <p>The second step addresses the semantic alignment challenge by mapping extracted IFC data to
suitable vocabularies and ontologies. This process employs domain ontologies including BOT [7, 27],
SOSA/SSN [21], and DOT [10]. Where no suitable classes or properties are available in existing
ontologies, custom extensions are defined using the LifeMACS Ontology (LFM) to represent aspects
such as Bayesian uncertainties and concrete properties. The mapping engine implements rule-based
transformations that convert IFC identifiers and relationships into corresponding triples, ensuring
consistent naming conventions and stable Uniform Resource Identifiers (URIs) across the dataset as
well as keeping the one-to-one connection to the original IFC object via its global ID (GUID).</p>
        <p>The third step stores and serves the resulting RDF graphs through a triple store or linked data
platform. This component provides interfaces for data querying and manipulation (e.g., via SPARQL),
supporting integrations with other semantic resources. For example, if structural monitoring data—
such as strain and temperature measurements—reside in separate repositories, alignment with SOSA
properties enables cross-dataset inference and retrieval.</p>
        <p>By combining separate data ingestion, ontology alignment, and linked data interaction, this
architecture accommodates evolving domain requirements and facilitates future extensions. In
particular, time-varying data or probabilistic model outputs were incorporated without extensive
modifications to the existing IFC data or underlying ontological models. This approach thus creates a
scalable and interoperable foundation for integrating BIM-based geometry and semantic data with
specialized workflows in asset management and structural health monitoring.</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Ontology Stack and Custom Extensions</title>
        <p>The LifeMACS (LFM) ontology adopts a modular design by importing and extending a series of widely
used ontologies to capture both general and specialized aspects of structural health monitoring,
building topology, and facility management. As shown in the ontology definition, the following key
ontological components are included:</p>
        <p>Building Topology Ontology (BOT) provides a concise hierarchy for built-environment
concepts, modeling relationships such as adjacency and containment. In the LifeMACS ontology,
elements representing physical infrastructure are aligned with bot:Element.</p>
        <p>Ontology for Properties and Materials (OPM) is employed to capture material characteristics
and property states. In the LifeMACS ontology, the object property lfm:hasPropertyState references
opm:PropertyState, enabling time-dependent descriptions of evolving material or structural
properties.</p>
        <p>Semantic Sensor Network and Sensor, Observation, Sample, and Actuator (SSN/SOSA) are
used to describe sensor networks, their observations, and more generally measurements or inspections
done. The LifeMACS ontology extends this framework through properties including
lfm:hasUncertainty.</p>
        <p>Damage Topology Ontology (DOT) is imported to represent damage phenomena, such as
cracking or spalling. Instances of dot:Damage can be linked to specific structural components using
lfm:hasDamageAssessment.</p>
        <p>OWL-Time supplies constructs for representing temporal concepts, such as intervals using
time:Interval and specific time points via time:Instant. The LifeMACS ontology references for example
time:Interval through properties like lfm:hasValidityPeriod or lfm:hasTimeInterval.</p>
        <p>Domain-Specific Extensions (LifeMACS Ontology LFM). Classes such as lfm:BayesianModel
and lfm:DegradationModel capture the computational models used for predicting structural
performance, while lfm:Parameter and lfm:ProbabilityDistribution enable descriptions of uncertainty
in material or model parameters. Furthermore, properties such as lfm:hasIfcRepresentation support
linking each LFM individual to its corresponding IFC entity. Additional relationships like
lfm:hasFiniteElementModel and lfm:hasCorrosionLevel, ensure that specialized engineering
workflows and advanced simulation models are integrated into the overall knowledge graph. The full
ontology is available on GitHub1, as well as an overview of the classes and properties2.</p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. IFC-to-TTL Conversion Pipeline</title>
        <p>The conversion pipeline from IFC to RDF leverages a Python-based workflow, based on Figure 1, that
combines the IfcOpenShell library3 for parsing IFC data with the RDFLib framework for creating and
managing RDF triples. The pipeline is composed of the following sequential stages:</p>
      </sec>
      <sec id="sec-2-4">
        <title>2.3.1. Initialization of Namespaces and Graph Context</title>
        <p>The pipeline initializes an empty RDF graph and binds the prefixes mentioned earlier in the ontology
stack.</p>
      </sec>
      <sec id="sec-2-5">
        <title>2.3.2. Spatial Structure Extraction</title>
        <p>The first task is to extract the hierarchy of spatial entities (e.g., sites, buildings, storeys, and spaces)
from the IFC file. In the provided implementation, IfcSite, IfcBuilding, IfcBuildingStorey, and IfcSpace
1 https://github.com/CedricDriesen92/LifeMACS_LD/blob/main/LFM.ttl
2 https://github.com/CedricDriesen92/LifeMACS_LD/blob/main/LFM.txt
3 https://ifcopenshell.org/
elements are iterated to create corresponding instances of BOT concepts (e.g., bot:Site, bot:Building,
bot:Storey, and bot:Zone). Relationships such as bot:hasBuilding, bot:hasStorey, and bot:hasZone are
then assigned based on the IFC decomposition structure. This process forms a backbone that captures
the building’s topology and enables downstream steps to attach new entities (e.g., building elements
or sensors) to the appropriate location.</p>
      </sec>
      <sec id="sec-2-6">
        <title>2.3.3. Building-Element Conversion</title>
        <p>Following the creation of the spatial hierarchy, the pipeline identifies the relevant concrete structural
components in the model, such as beams, columns, slabs, and walls. Each element is classified under
bot:Element and further specialized to lfm:ConcreteElement to indicate domain relevance for
reinforced concrete structures. Where available, the pipeline retrieves references to associated
materials (e.g., IfcMaterial) and stores them as property states within the OPM framework
(opm:PropertyState). These associations allow explicit representation of each element’s material
composition and extend potential analyses with domain-specific attributes (e.g., corrosion resistance).
Values that have Bayesian properties, such as an uncertainty distribution, are tackled by the LFM
ontology via lfm:hasProbabilityDistribution, lfm:mean, lfm:standardDeviation… Finally, each
converted entity (including sensor and damage entities) references the original IFC GUID via
lfm:hasIfcGlobalId, enabling round-trip interoperability with authoring tools.</p>
      </sec>
      <sec id="sec-2-7">
        <title>2.3.4. Sensor Integration</title>
        <p>Sensor data stored as IfcSensor objects are converted to corresponding SOSA classes, labeling each
sensor instance with sosa:Sensor. The pipeline also checks IFC property sets for additional metadata
(e.g., SensorID, current readings), which is used to create sosa:Observation triples. Temporally
relevant data are further annotated using constructs from the Time Ontology (time:Instant), enabling
queries about when a measurement was taken. Finally, Bayesian concepts are handled similar to the
building elements. This linkage of sensor readings with Bayesian properties to specific building
elements or zones supports real-time structural health monitoring use cases.</p>
      </sec>
      <sec id="sec-2-8">
        <title>2.3.5. Damage Modeling</title>
        <p>The final conversion step addresses damage information that may be embedded in
IfcBuildingElementProxy objects. Properties such as crack length, crack width, and crack depth are
detected from relevant IFC property sets. A new dot:Damage instance is generated for each identified
defect, and the pipeline associates that instance with its host element through a property such as
lfm:hasDamageAssessment. Uncertainties and other Bayesian properties are handled similar to the
building elements and sensors. By adopting DOT concepts and linking them to BOT elements, the
pipeline preserves both the location and nature of each damage instance.</p>
      </sec>
      <sec id="sec-2-9">
        <title>2.3.6. Output Generation</title>
        <p>Once the hierarchical, elemental, sensor, and damage information has been converted, the pipeline
serializes the complete RDF graph to Turtle format. This final output may be stored locally for offline
analysis or ingested into a triple store for SPARQL-based queries. The serialization step ensures that
geometry, topology, and domain-specific attributes are accessible within a single, standards-compliant
graph.</p>
      </sec>
      <sec id="sec-2-10">
        <title>2.3.7. Conclusion</title>
        <p>Through these discrete stages, the pipeline maintains a separation of concerns between data parsing,
semantic enrichment, and RDF output. Specialized Python classes manage the consistency of URIs,
while modular functions handle conversions for spatial structure, building elements, sensors, and
damages in a reproducible manner. In this manner, the resulting RDF representation reflects both
standard building information (in line with IFC and BOT) and specialized life-cycle aspects (e.g., crack
measurements, time-stamped sensor observations, probability distributions), allowing for flexible
queries and analytics in structural health monitoring and facility management contexts. The full code
is available on GitHub4.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Experimental Setup and Evaluation</title>
      <p>This section outlines the experimental procedure adopted for converting IFC data to a Linked Data
representation within a real-world context. The evaluation focuses on a reinforced concrete bridge
case study, selected for its representative structural configuration, active monitoring regime, and the
presence of measurable deterioration processes. After describing the test environment and data
preparation steps, key outcomes of the IFC-to-LBD conversion are presented.</p>
      <sec id="sec-3-1">
        <title>3.1. Case Study: Reinforced Concrete Bridge</title>
        <p>The experimental validation centered on a Belgian mid-20th-century reinforced concrete bridge
known to exhibit multiple forms of damage (cracks, spalling, rebar corrosion…). This structure was
constructed in the late 1950s and has been subjected to incremental retrofitting and repairs, making it
an ideal candidate for testing the capacity of the Linked Data approach to capture both historical
and newly acquired data. Examples of the damage can be seen in Figure 2.</p>
        <p>A digital model of the bridge was compiled from historical plans and laser scanning. The resulting IFC
file served as the starting point for the IFC-to-LBD conversion pipeline. In parallel, a set of sensor
measurements—collected via strain gauges and temperature probes distributed over critical structural
regions—provided time-series observations indicative of the bridge’s real-time performance.
4 https://github.com/CedricDriesen92/LifeMACS_LD/blob/main/IFCtoLD.py
Additional inspection data, including detail on crack dimensions and material properties, were
collected during visual assessments and stored in specialized property sets within the IFC model. The
resulting IFC model can be seen in Figure 3, with the cubes representing the sensors and their
coloration showing the current sensor strains.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Data Preparation and Pipeline Configuration</title>
        <p>Prior to executing the conversion, the IFC model was refined to ensure internal consistency and
uniform naming conventions. Elements corresponding to beams, columns, walls, and slabs were
verified to include valid standardized property sets specifying both geometry and condition. Sensors
in the IFC model were recorded as IfcSensor elements, while defects were cataloged in
IfcBuildingElementProxy objects with custom property sets to store crack lengths or spalling area
including probability distributions and related concepts, as well as damage types. For simplicity, in
this work time dependent data is stored directly in the graph, while for real use cases to avoid making
the graph too large a system integration based approach using for example IoT and database
workflows should be considered.</p>
        <p>The Python-based conversion pipeline (Section 2.3) was configured to:
1. Extract Spatial Hierarchy – Identify the site, building (if applicable), and storey
relationships and map them to BOT classes (bot:Site, bot:Building, bot:Storey).
2. Enrich Concrete Elements – Classify beams, columns, slabs… as lfm:ConcreteElement for
subsequent domain-specific queries (e.g., corrosion-level checks, Bayesian model
parameters).
3. Capture Sensor Observations – Convert IfcSensor instances to sosa:Sensor and generate
related sosa:Observation individuals, each annotated with the relevant timestamp and
Bayesian properties.
4. Link Damage Instances – Detect damage property sets (e.g., crack length, crack depth…)
with and convert them to DOT-based damage classes (dot:Damage) with inclusion of Bayesian
parameters. The property lfm:hasDamageAssessment was used to associate structural
components with specific defect instances.
5. Maintain Link to IFC – A property lfm:hasIfcGlobalId is added to all concrete, sensor, and
damage elements, with the property value linked to the IFC GUID.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Conversion Results and Observations</title>
        <p>Following the pipeline execution a graph is returned reflecting both the high-level spatial structure
(site, storeys, spaces) and detailed elements (concrete sections, sensor data, damage descriptors,
uncertainty distributions). Initial inspection of the generated graph indicated that the semantic classes
and properties accurately mirrored the specified ontology design.</p>
        <p>Spatial concepts were properly instantiated as bot:Site, bot:Building, bot:Storey, and bot:Zone, with
containment relationships (e.g., bot:hasStorey) ensuring navigability across levels.
Beams, columns, and slabs retained standard bot:Element membership while also inheriting
domainspecific traits via lfm:ConcreteElement.</p>
        <p>Each recorded damage instance was expressed as a dot:Damage, carrying quantitative attributes
(length, width…) organized under opm:PropertyState as either standard values or uncertainty
distributions as well as receiving the required DOT properties such as damage type. This arrangement
allowed queries linking defective areas to material states and inspection time frames.</p>
        <p>A total of 274 IfcSensor elements produced sosa:Sensor objects, enabling creation of corresponding
sosa:Observation instances with distinct time stamps. Observations included (temperature corrected)
strain or temperature values tied to specific concrete elements or zones, permitting time-based
analyses of structural response, as either values or uncertainty distributions.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Results and Discussion</title>
      <p>This section interprets the outcomes described in Section 3, analyzing how the proposed pipeline and
ontology stack enhance data usage beyond conventional IFC-centric workflows. The discussion
situates these observations within the broader context of Linked Data adoption in the AEC industry,
both the advantages as well as the limitations.</p>
      <sec id="sec-4-1">
        <title>4.1. Example RDF output and SPARQL query</title>
        <p>Following the pipeline execution, a graph of over 4600 RDF triples was generated from the IFC file of
the case study bridge, available for viewing on GitHub5 and exported from Revit 2024 in the IFC 4.3
format. Below in Listing 1 is a short excerpt from this graph illustrating how a damage element might
be modeled in Turtle. Suppose an IfcBeam with GUID “0VwJW5Qw3E2uMg8ZhXPz5A” has a damage
with GUID “1FsUCh_1n6AAe2OZ$QBHTi”, with crack length stored as a normal distribution with a
mean of 17.2 mm and standard deviation of 1.2 mm.
1 # Concrete element hosting a damage
2 lfm:element_b9a2457e-24dd-4abc-b91d-50767b1560bc
3 a bot:Element, lfm:ConcreteElement ;
4 lfm:hasIfcRepresentation “IfcBeam” ;
5 lfm:hasIfcGlobalId "0VwJW5Qw3E2uMg8ZhXPz5A" ;
6 # Indicate that this element has a damage instance (crack)
7 lfm:hasDamageAssessment lfm:damage_3f1dac7a-6a5b-471b-b72e-a847716a2301 .
8
9 # Damage instance
10 lfm:damage_3f1dac7a-6a5b-471b-b72e-a847716a2301
11 a dot:Damage ;
12 rdfs:label " crack_1" ;
13 lfm:hasIfcGlobalId "1FsUCh_1n6AAe2OZ$QBHTi" ;
14 # Instead of a single numeric crack length, we store a property state referencing a probability distribution
15 lfm:hasPropertyState lfm:property_state_9e5d8ba6-87cc-49f2-a719-5e35c315f711 .
16
17 # Property state holding the distribution info
18 lfm:property_state_9e5d8ba6-87cc-49f2-a719-5e35c315f711
19 a opm:PropertyState ;
20 opm:propertyName "Crack Length" ;
21 prov:generatedAtTime “2024-07-23T12:00:00Z”^^xsd:dateTime
22 # We link to a NormalDistribution instance
23 lfm:hasProbabilityDistribution lfm:normalDist_32c68ab0-2f14-4c94-9d3f-0aef47b10f06 .
24
25 # The NormalDistribution instance
26 lfm:normalDist_32c68ab0-2f14-4c94-9d3f-0aef47b10f06
27 a lfm:NormalDistribution ;
28 lfm:mean "17.2"^^xsd:float ;
29 lfm:standardDeviation "1.2"^^xsd:float .</p>
        <p>Listing 1: An example of a damage element in Turtle following the LifeMACS ontology stack
Querying this graph is done by SPARQL query. For example, the query in Listing 2 retrieves all
damages longer than 15 mm at p &lt; 0.05 for normal distributions, as well as their hosts and other useful
properties:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24 }</p>
        <p>SELECT ?element ?elementGuid ?damage ?damageGuid ?meanValue ?stdValue ?lower95
WHERE {
?element a lfm:ConcreteElement ;
lfm:hasIfcGlobalId ?elementGuid ;
lfm:hasDamageAssessment ?damage .
?damage a dot:Damage ;
lfm:hasIfcGlobalId ?damageGuid ;
lfm:hasPropertyState ?ps .
?ps a opm:PropertyState ;
opm:propertyName "Crack Length" ;
lfm:hasProbabilityDistribution ?dist .
?dist a lfm:NormalDistribution ;
lfm:mean ?meanValue ;
lfm:standardDeviation ?stdValue .
# Calculate 95% lower bound for damage length = mean - 1.645 * std
BIND(xsd:float(?meanValue) - 1.645 * xsd:float(?stdValue) AS ?lower95)
# Filter to return only those cracks whose lower 95% bound is &gt; 15 mm</p>
        <p>FILTER(?lower95 &gt; 15)
Listing 2: A SPARQL query to retrieve damage elements passing a certain uncertainty threshold
Another example is the SPARQL query in Listing 3, designed to retrieve all latest sensor measurements
along with their structural element hosts. Results of a similar query including e.g. spatial coordinates,
material properties, uncertainty values… could be fed to a structural FEM-tool.</p>
        <p>SELECT ?structuralElement ?elementType ?sensorId ?measurementType ?value ?unit ?timestamp
WHERE {
# Get structural elements with sensors
?structuralElement a lfm:ConcreteElement ;
rdf:type ?elementType ;
lfm:hasSensor ?sensor .
Beyond these simple examples one can imagine that, for example, automatic queries of the sensor
strain values could lead to automated warnings sent out if certain simulated uncertainty thresholds
are crossed.</p>
      </sec>
      <sec id="sec-4-2">
        <title>4.2. Advantages over Traditional Workflows</title>
        <p>The experimental findings, such as the examples preceding this section, demonstrate that migrating
from a standard IFC file to a Linked Data representation yields several tangible benefits. First, elements
such as IfcBeam or IfcColumn become more than static geometric objects once mapped to
lfm:ConcreteElement and annotated with domain-specific properties (e.g., damage state, corrosion
level, sensor readings). This enriched semantic model permits more direct and flexible queries—such
as retrieving all structural members with high corrosion levels, having sensor readings above a defined
strain threshold, or crack lengths exceeding a specified limit at a certain level of confidence—that
would otherwise require substantial custom coding or a more complicated workflow.</p>
      </sec>
      <sec id="sec-4-3">
        <title>4.2.1. Improved Interoperability and Integration</title>
        <p>By aligning IFC concepts with recognized ontologies the resulting graph supports cross-platform data
sharing and integration with other Linked Data resources (e.g. the LifeMACS buildingSMART Data
Dictionary6 or other external knowledge bases could easily be implemented).
6 https://search.bsdd.buildingsmart.org/uri/bw/LM</p>
        <p>In the LifeMACS project, among multiple simulation tools (e.g., Bayesian calculation software,
finite element packages…), ease-of-use is also increased. Instead of relying on ad hoc code or
intermediate export/import routines, these external tools only need to reference well-defined SPARQL
endpoints for the single source of truth graph, retrieving exactly the data required.</p>
      </sec>
      <sec id="sec-4-4">
        <title>4.2.2. Addressing Time-Dependent and Probabilistic Aspects</title>
        <p>Time-based analysis and probabilistic modeling pose particular challenges when using traditional IFC
data structures, which are typically static snapshots of an asset. The proposed ontology and pipeline
mitigate these challenges by employing properties from OWL-Time to record observation timestamps,
and by introducing custom classes (e.g., lfm:ProbabilityDistribution, lfm:BayesianModel,
lfm:NormalDistribution…) to handle stochastic parameters. This opens a pathway for explicitly
linking real-time sensor updates or evolving crack measurements to uncertainty models, supporting
more robust lifecycle assessments.</p>
      </sec>
      <sec id="sec-4-5">
        <title>4.2.3. Opportunities</title>
        <p>While the present case study focused primarily on strain and temperature sensors, the semantic layer
is readily extensible to incorporate other data feeds, such as acoustic emission sensors or advanced
image-based inspection. Each can be natively represented in SOSA/SSN to ensure standardized
observations, procedures, and results.</p>
        <p>When integrated into a triple store, the previously mentioned capabilities enable structural
engineers and facility managers to carry out more complex investigations (e.g., analyzing damage
growth over time in tandem with stress variations) without leaving a single data environment. This is
a key advantage over file-based IFC workflows, which often compel stakeholders to use
domainspecific applications that can only exchange partial datasets.</p>
      </sec>
      <sec id="sec-4-6">
        <title>4.3. Practical Performance and Usability Considerations</title>
        <p>The prototype implementation successfully handled the 10.0 MB bridge IFC data7 within a runtime of
less than 0.1 s on a system with an Intel® i7-13700, with the result being returned in TTL format8.
However, performance could degrade for significantly larger and more complex models, prompting
the need for potential optimizations (parallel parsing, incremental conversion).</p>
      </sec>
      <sec id="sec-4-7">
        <title>4.4. Limitations and Future Opportunities</title>
        <p>Despite the clear advantages this methodology presents, a number of limitations remain:
1. Geometry Representation</p>
        <p>Although basic spatial constructs (building, storey, zone) have been aligned with BOT,
detailed 3D geometry is still stored in the source IFC file. More sophisticated handling, either
via other ontologies such as GeoSPARQL [24] or OMG/FOG [22, 23] or more thorough IFC
connection, may be necessary for domain applications requiring advanced spatial queries.
2. Ontology Completeness</p>
        <p>The LifeMACS ontology currently emphasizes structural and damage-related concepts
specific to concrete structures. Adapting or expanding this framework to other domains (e.g.,
mechanical/electrical systems, occupant comfort) would require further ontology refinement
and potentially additional alignments with industry standards.</p>
        <p>3. Data Quality and Governance
7 https://github.com/CedricDriesen92/LifeMACS_LD/blob/main/W20.ifc
8 https://github.com/CedricDriesen92/LifeMACS_LD/blob/main/W20.ttl
As with any semantic integration, the pipeline’s efficacy depends on the accuracy and
consistency of input data. Missing or mislabeled attributes in IFC can lead to incomplete RDF
graphs. Implementing systematic validation checks or “pre-flight” data cleanup routines is
recommended to ensure semantic accuracy.
4. Scalability for Large Infrastructure Networks</p>
        <p>While the present approach showed feasibility at the level of a single bridge, major
infrastructure owners may oversee hundreds of structures. Future work should investigate
the performance and user workflow implications of simultaneously processing queries on
multiple transformed IFC models.</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>5. Conclusions and Outlook</title>
      <p>The results reaffirm that Linked Data techniques, when properly integrated with IFC workflows, can
substantially enhance the management of complex infrastructure data. Bridging geometry and
semantically rich domain ontologies allows asset managers to track and query real-time condition
indicators, plan maintenance interventions more effectively, and align with state-of-the-art Bayesian
modeling and simulation approaches. Although practical hurdles remain (e.g., geometry complexities,
adoption by industry professionals), the positive feedback from experts in the LifeMACS project
reinforces the potential of IFC-to-LBD integration for real-world SHM and facility management
scenarios.</p>
      <p>Building on these findings, future research and development could focus on improving geometry
serialization into RDF, refining domain-specific ontologies for complementary use cases (e.g., steel or
masonry structures), and scaling the solution for large-scale infrastructure portfolios. Continued
collaboration with industry stakeholders will be crucial to ensuring that these semantic advancements
can be seamlessly integrated into day-to-day engineering and management workflows, ultimately
creating a more efficient, interoperable, and intelligent future for AEC data management.</p>
    </sec>
    <sec id="sec-6">
      <title>Acknowledgements</title>
      <p>The research was done within the FWO SBO project LifeMACS: Multi-layer Bayesian life-cycle
Methodology for the Assessment of existing Concrete Structures, supported by FWO-Flanders
(FWOSBO project S001021N).</p>
    </sec>
    <sec id="sec-7">
      <title>Declaration on Generative AI</title>
      <p>During the preparation of this work, the author used Google Gemini in order to help with
grammar/spelling checks, and rewording. After using this tool/service, the author(s) reviewed and
edited the content as needed and take(s) full responsibility for the publication’s content.
21. Janowicz, K., Haller, A., Cox, S.J.D., Le Phuoc, D., Lefrançois, M.: SOSA: A lightweight ontology
for sensors, observations, samples, and actuators. J. Web Semant. 56, 1–10 (2019).
https://doi.org/10.1016/j.websem.2018.06.003
22. Bonduel, M., Wagner, A., Pauwels, P., Vergauwen, M., Klein, R.: Including widespread
geometry formats in semantic graphs using RDF literals. Presented at the 2019 European
Conference on Computing in Construction July 10 (2019)
23. Wagner, A., Bonduel, M., Pauwels, P., Uwe, R.: Relating geometry descriptions to its
derivatives on the web. Presented at the 2019 European Conference on Computing in
Construction July 10 (2019)
24. Battle, R., Kolas, D.: GeoSPARQL: Enabling a Geospatial Semantic Web.
25. Bonduel, M., Oraskari, J., Pauwels, P., Vergauwen, M., Klein, R.: The IFC to Linked Building</p>
      <p>Data Converter - Current Status.
26. Wagner, A., Bonduel, M., Werbrouck, J., McGlinn, K.: Geometry and geospatial data on the
web. In: Buildings and Semantics. CRC Press (2022)
27. Schneider, G.F.: Towards Aligning Domain Ontologies with the Building Topology Ontology.
(2017). https://doi.org/10.13140/RG.2.2.21802.52169</p>
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