ATMO: Autonomous Train Map Ontology
Nadia Chouchani
a
and Sana Debbech
b
IRT Railenium, Technopole Transalley 180, rue Joseph-Louis Lagrange, 59308 Valenciennes Cedex, France
Keywords:
Ontology Engineering, Modularization, Model-Based Engineering, Conceptual Modelling, Autonomous Train
Abstract:
Infrastructure is the backbone of the railway industry which is an extensive and particularly complex system.
However, the usage of different national and international standards for its design has led to a large number of
incompatible systems. In this paper, we present ATMO, Autonomous Train Map Ontology, a modular ontology
for modelling an on-board digital map for autonomous trains representing the railway infrastructure, line-side
signalling and associated buildings. Semantic web technologies, knowledge and ontology engineering are
adopted to integrate information from heterogenous sources and diverse standards such as RailSystemModel,
EULYNX and IFC Rail ; to ensure semantic consistency of digital map objects. The development process is
based on METHONTOLOGY and produced : (i) UML model as lightweight ontology; and (ii) OWL formal
machine-readable specification as heavyweight ontology. The latter was evaluated using a railway use case.
1 INTRODUCTION
Physical infrastructures such as railway networks are
key elements for passenger and freight transport.
Modelling rail infrastructure is a critical process be-
cause of the heterogeneity of the information to be
modelled such as tracks, signalling and control sys-
tems ; as well as safety regulations, engineering con-
ventions and design rules to be respected. As part of
the autonomous train project, we are working on the
modelling of the railway digital map ; based on dif-
ferent standards. It includes all information on phys-
ical tracks, signalling assets and even buildings such
as tunnels and bridges, eventually in 3D representa-
tion. Data integration and interoperability are com-
plex challenges for this task consisting on modelling
a complete and extensive digital map ; due to the het-
erogeneous nature of data and underlying standards.
To overcome this problem, we propose to apply se-
mantic data modelling techniques to allow integration
of heterogeneous information and make consistency
of mapping elements. In this paper, we adopt recent
researches in semantic web, ontology engineering
and information architecture to develop Autonomous
a
https://orcid.org/0000-0002-2660-1352
b
https://orcid.org/0000-0002-4003-6505
This research work is funded by the French program
“Investissements d’Avenir” and is part of the French collab-
orative project TASV (Train Autonome Service Voyageurs),
with Railenium, SNCF, Alstom Crespin, Thales, Bosch, and
Spirops.
Train Map Ontology, ATMO, a modular ontology for
autonomous train on-board map. As developing on-
tologies is not an easy task, it is compulsory to re-
strict the studied domain knowledge (Gruber, 1993).
Our proposed solution represents a railway map on-
tology, which will describe the concepts and relations
related to infrastructure, signalling and BIM (Building
Information Modelling) (BSI, 2022). Its usefulness
consists in ensuring interoperability, defining com-
mon domain knowledge and its sharing. ATMO feder-
ates knowledge from different source models or rail-
way standards such as RailSystemModel, RSM (UIC,
2022) and IFCRail (BSI, 2022) that are initially devel-
oped separately and use different terminology of rail-
way system components. In this sense, ATMO will be
exploited by multidisciplinary stakeholders and dif-
ferent subsystems of autonomous trains such as envi-
ronment monitoring during the description of the oc-
currence of train stations, tunnels, etc. ; and the ATO-
OB, Automatic Train Operation On-Board, to identify
the topological description of the railway network.
Competency questions of ATMO are raised to de-
fine which precise kind of information this seman-
tic model will provide. Here the adopted methodol-
ogy is METHONTOLOGY (Fernandez-Lopez et al.,
1997) whose choice will be justified in the follow-
ing section. It has resulted in, first, lightweight ontol-
ogy represented using a UML
1
conceptual model, and
second, heavyweight ontology as machine-readable
specification obtained by applying a Model Based En-
1
https://www.omg.org/spec/UML/2.0
Chouchani, N. and Debbech, S.
ATMO: Autonomous Train Map Ontology.
DOI: 10.5220/0011893200003402
In Proceedings of the 11th International Conference on Model-Based Software and Systems Engineering (MODELSWARD 2023), pages 283-290
ISBN: 978-989-758-633-0; ISSN: 2184-4348
Copyright
c
2023 by SCITEPRESS Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
283
gineering transformation from UML to OWL
2
. ATMO
is developed to fulfill the following Research Goal
(RG):
RG. How to provide a structured and shared view of
autonomous train map concepts and their relations in
order to deal with the semantic heterogeneity of rail-
way standards?
The remainder of this paper is organised as fol-
lows. In section 2, we present a background on the
existing data models, standards and related work. In
section 3, we detail the methodological framework of
the ontology development. In section 4, we discuss
the obtained results. Finally, we conclude and de-
scribe future works.
2 RELATED WORK AND
MOTIVATIONS
An ontology is defined as an explicit formal specifica-
tion of a conceptualisation model which is an abstrac-
tion of a domain of interest (Gruber, 1993). It was ex-
ploited in many domains specially for Safety Critical
Systems (SCS) (Uschold and King, 1995). Ontolo-
gies have powerful capabilities to represent knowl-
edge from different domains and ensure their fed-
eration and semantic clarification. Reasoning using
the machine-readable version allows an efficient com-
munication between stakeholders involved in the de-
velopment process of SCS. Furthermore, the imple-
mented ontology facilitates the decision-making pro-
cess by data retrieval and ensures traceability of safety
decisions and design choices. However, the ontology
development process is costly and time consuming.
In order to reduce its complexity, the concept of mod-
ular ontologies has been introduced (D’Aquin et al.,
2009). Being an incremental process, modularization
offers a scalable and efficient development. This pro-
cess is the composition of an ontology into smaller
modules. The latter can then be partially reused,
which improves the management of the complexity
of the ontology and the associated reasoning (Pathak
et al., 2009). An ontological module is therefore de-
fined as a reusable component of a larger and more
complex ontology. To be reused, this component must
be autonomous, i.e logically coherent and indepen-
dent of the other modules (Pathak et al., 2009). Nev-
ertheless, it must be connected to it without being iso-
lated or dis-joined to form a single coherent ontology.
Moreover, its deletion does not affect the ontology as
a whole. As a description of the railway infrastructure
can contain several aspects and views of the system
2
https://www.w3.org/TR/owl2-syntax/
such as signalling, track construction or the catenary
network, modularity seems to be a suitable solution
for the development of ATMO. Indeed, each module
would be devoted to a view of the infrastructure dig-
ital map. This ensures semantic cohenrencies when
ansewring the multidisciplinary users and needs of the
digital map.
Several methodologies for ontologies develop-
ment, which vary according to the context of use
of the ontology and the target users, have been pro-
posed. A methodology is defined in IEEE std.730.1
as “a comprehensive, integrated series of techniques
or methods creating a general systems theory of how
a class of thought-intensive work ought to be per-
formed” (IEEE, 1996).
These methodologies have been classified into
four groups according to their characteristics and pur-
pose (Debbech, 2019). Early methods such as EN-
TERPRISE (Uschold and King, 1995) assumes a sin-
gle, non-iterative design process. The second cate-
gory includes iterative methods that emphasise initial
formal specification and advocate the reuse of exist-
ing models and ontologies, such as METHONTOL-
OGY (Fernandez-Lopez et al., 1997). A third class
includes post-semantic web methods such as SABiO
(de Almeida Falbo et al., 1998) a systematic approach
that emphasises collaboration and flexibility. And fi-
nally ontological learning methods which are based
on the use of automated or semi-automated tools to
reconfigure knowledge.
In our case, we are based on existing standards
for modelling the railway infrastructure. This moti-
vates our choice of METHONTOLGY which allows
this reuse and adaptation. Moreover, it is the only one
which specifies in its steps how the ontology will be
populated.
Recently, semantic data models have been pro-
posed allowing data context storing in a machine-
readable format (Berners-Lee et al., 2001). In this
context, some ontologies for the railway domain are
proposed. InteGRail, a project led by the European
Union’s (EU) 7th Framework Program (FP7) de-
signed a standard approach for architecture and com-
munication (InteGRail, 2022). One developed ontol-
ogy (RDO) was intended to create an opportunity for
improved performance. Another research work pro-
posed a domain ontology for railways which aims
to integrate information from heterogeneous sources
(Tutcher et al., 2017). Based on semantic web, it
presents a proof-of-concept real time passenger infor-
mation system.
Regarding railway infrastructure, there are some
modelling standards. RailSystemModel (RSM) is a
conceptual model which is partly devoted to mod-
MODELSWARD 2023 - 11th International Conference on Model-Based Software and Systems Engineering
284
elling this part of the rail system (UIC, 2022). Based
on ISO 19148 for Linear Referencing
3
, RSM provides
a description of the railway infrastructure based on
the topology of the track. The latter is represented by
objects in the Topology package which are the carri-
ers of other information. This description is based, on
the one hand, on an operational breakdown of the net-
work infrastructure in the Network package and on
the positioning of these objects on the earth’s geode
through association with concepts from the Position-
ingSystem” package. The information attached to the
topology can be geometric in the context of the Lo-
cation package and/or functional in the context of
the NetEntity package. IFC Rail norm attempts to
represent the geometry of construction tracks based
on the Building Information Modelling (BIM) (BSI,
2022). Finally, the EULYNX model includes a large
set of objects relating to signalling objects (signals,
locks, etc.) and related concepts (routes, needle pro-
tection, etc.) (EULYNX, 2022). Its main purpose is
to allow interoperability through the exchange of sig-
nalling information between infrastructure managers
and signalling system providers.
The work presented in this paper is situated at the
intersection of several domains. Our motivation is to
model a digital map for autonomous train by devel-
oping a modular ontology. The modularization al-
lows semantic knowledge to be presented in a struc-
tured, formal and expressive model. We noticed that
METHONTOLOGY, whose steps are shown in the
Figure 1, is the most suitable methodology for our use
case.
In the literature, one common problem in design-
ing semantic models for railway is the lack of use
of international standards. Therefore, our choice of
knowledge sources is based on RSM, EULYNX and
IFC Rail. To the best of our knowledge, our work
is the first to propose such a mapping between stan-
dards for semantic modelling of on-board railway dig-
ital map.
3 METHODOLOGICAL
FRAMEWORK
In this work, we have adopted the ontological mod-
ularity for modelling the on-board railway map. The
idea is to define individual modules, as shown in fig-
ure 2 which are then assembled in the same modu-
lar ontology ATMO. The latter allows reasoning on
knowledge of the field of railway digital map. Its
3
https://www.roadotl.eu/static/eurotl-
ontologies/iso19148 doc/index-en.html
Figure 1: The methodology METHONTOLOGY: activities
and steps.
Figure 2: Overall approach of ATMO development: (1)
knowledge extraction; (2) ontology modules construction;
and (3) final ontology composition.
development requires to acquire knowledge from ex-
perts in various fields and reuse existing resources and
finally to compose the first developed modules. Each
module has been developed respecting the methodol-
ogy METHONTOLOGY.
In the following, we present the general frame-
work of the developed modules, from the specifica-
tion to the evaluation.
3.1 Specification
In this step, we defined high level requirements. The
scope being the railway map, this ontology will an-
swer the questions of interoperability of national and
international systems and standards as well as the
reuse of domain knowledge. This semantic model
can be used for the implementation of on-board au-
tonomous train map, and also for the project carried
out by the International Union of Railways (UIC)
aiming to creating a global dictionary for the rail-
way domain. Different modules have been defined
ATMO: Autonomous Train Map Ontology
285
according to the reuse, the domain and its level of de-
tail; which are: “Railway”, “Track”, “TrackSide” and
“Operational”.
The specification of the data model is defined by
a set of functional and non-functional requirements
derived from the established needs of the implemen-
tation of the autonomous train.
3.2 Knowledge Acquisition
Several areas of knowledge are at the heart of this
work. This step was carried out by defining Ontol-
ogy Design Patterns (ODPs). It involves defining all
the concepts to be used in the ontology, the relation-
ships between them and also a documentation corre-
sponding to the different concepts. In order to extract
knowledge from the domain of the ontology, we used
three sources for explicit and implicit acquisitions.
First bibliographic research of articles and books was
necessary to form a background on the whole field
and questions on more specific use cases. Then we
collaborated with experts, especially in the signalling
field. We had discussions around EULYNX UML
model to which we had a read access. Finally, the
reuse and reengineering of non-ontological resources
were applied to the construction of the different mod-
els. The analysis of the various cited resources al-
lowed to define a knowledge model that meets the
needs covered by the ATMO ontology.
The two approaches “top-down” and “re-use”
were used to extract knowledge for the ontology.
Each module of the latter was created by repeatedly
iterating over these two approaches. The first relies
on the knowledge of experts to build a model. It com-
prises the following stages:
1. Determine the concepts within the scope of the
ontology after discussing with experts;
2. Decompose the concepts into subcategories
around which to create competency questions;
3. Examine the scope of new concepts in order to de-
cide whether they will be implemented or reused
according to the re-use approach;
4. Re-engineer the concepts where appropriate.
During this process, the method “top-down”
aimed to develop a high quality model for the knowl-
edge of on-board map in order to model it exhaus-
tively and fill the lack of links between the models
when reusing existing ones. As for the second ap-
proach of “re-use’, knowledge is extracted from exist-
ing models. It revolves around the following stages:
1. Identify the concepts to be reused after iterations
of the two approaches ;
2. Examine the documentation in order to analyse
the semantics of the concepts;
3. Re-engineer the concepts in the model by reusing
or extending it from existing models, respecting
the following methodology:
Refer to RSM where useful ;
Acknowledge the dual nature of concepts by in-
stantiating several classes;
Avoid mutual and strong dependencies;
4. Consider new questions of competency on the
new concepts within the scope of the ontology.
3.3 Conceptualisation
During the previous step, the basic concepts and
classes specific to the domain are identified. In our
work, three main categories of knowledge must be
represented in the model, which are the following :
Infrastructure: includes the topological descrip-
tion of the railway network as well as all the ge-
ographic data making it possible to geo-locate the
train in a 3D representation;
Signalling: involves the recognition of the vari-
ous signals encountered by the train, more specif-
ically their structures;
Building Environment: describes the occurrence
of buildings on the network such as stations,
bridges and tunnels, this then enables the environ-
mental monitoring subsystem to be supplied.
Based on these types of knowledge and the spec-
fication, a set of informal competency questions ex-
presses the problem solving goals. In the initial
ATMO prototype, some of the competency questions
are listed below :
How can an autonomous train be geo-located in a
3D representation ?
Which are the signals encountered by a train along
the route ?
What is the global environment in the network in-
cluding tunnels, bridges and stations ?
Answering these questions was carried out by build-
ing and extracting knowledge from domain models
and experts. The vocabulary and the ATMO model
modules are mainly based on the elements of RSM,
IFC Rail and EULYNX, relying on both their UML
models and natural language documentation. In fact,
the used modelling language of the lightweight ontol-
ogy is UML. This language provides a standard and
tool-supported notation. In addition, the sources mod-
els are designed in the same language.
MODELSWARD 2023 - 11th International Conference on Model-Based Software and Systems Engineering
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Figure 3: An excerpt of the “Track” UML package.
The designed model contains four packages, each
one references one module of the ATMO ontology.
Excerpts from the UML packages of “Track” and
“TrackSide” are shown, respectively, in figure 3 and
figure 4. We have chosen a modular design from the
beginning of the development cycle. The methodol-
ogy of this design follows a composition approach.
The different modules, each corresponding to a di-
mension of the railway map, are constructed and sub-
sequently composed to constitute the global ontology.
3.4 Integration
The reuse of ontological resources could not be im-
plemented because if there are ontologies in the rail-
way domain, standards like RSM and IFC are not
used. Nevertheless, the research of such resources
was carried out by exploiting the ontology search en-
gines as well as bibliographic searches. However, we
have reused existing vocabularies and concepts from
the standards mentioned above. Table 1 provides a
documentation of some of the reused concepts.
3.5 Implementation: From Lightweight
to Heavyweight Ontology
For mapping the UML model to the ATMO modular
ontology, we have used the Model-Based Engineer-
ing (MDE) approach. Based on the OMG classical
Model-Based Architecture, MDE ensures automatic
generation of the ontological modules from the UML
packages. Using these packages, the modules have
been generated in OWL/XML automatically. OWL is
the ontology encoding language used to implement
ATMO. Based on description logic, it is a standard
language to represent knowledge in semantic web
assuring interoperability. The transformation from
UML to OWL/XML is shown in the figure 5.
The transformation process is divided into two
steps : first the ATMO model is generated and con-
forms to the OWL Metamodel. Second, the ontology
is created in OWL/XML format. The ATL rule exe-
cuting this transformation is detailed in the figure 6.
ATMO: Autonomous Train Map Ontology
287
Figure 4: An excerpt of the “TrackSide” UML package.
Figure 5: ATL transformation from UML to OWL/XML.
3.6 Evaluation
A first evaluation of the developed lightweight ontol-
ogy was carried out by one of the project partners in
relation to the requirements specified in the specifi-
cations. ATMO heavyweight ontology evaluation was
defined in the context of two concepts : verification
and validation. From this perspective, we created sev-
eral instances. During ontology instantiating, we ver-
ified that all the needed information required to sup-
port the on-board map were represented.
A typical scenario of use for ATMO is supporting
the net entities positioning. In this scenario, a posi-
Figure 6: ATL rule transformation of UML package to on-
tological module.
tioning system supported by the ATMO on-board map
can geo-locate a signal in the railway network pre-
sented in figure 7.
Figure 7: Description of a railway network.
Geographical elements are collected and used to
create instances in the ontology. Let us suppose that
the system needs to know the position and location of
the signal “Signal 45”: individuals instanciating from
ATMO is shown in Figure 8.
MODELSWARD 2023 - 11th International Conference on Model-Based Software and Systems Engineering
288
Table 1: Documentation of some of the reused concepts.
Package Class Provenance Description
Track EntityLocation RSM The located net entities, such as a signal, have one
or more location relations. A location relation has
one “EntityLocation”. “SpotLocation”, “Linear-
Location” and AreaLocation” are kind of entity
location. They refer to network elements on the
topology.
LocatedNetEntity RSM It is a kind of “NetEntity” which represents a func-
tional object and is associated to a location.
TrackPanel IFC Rail The track is the logical element of a train line. In
terms of RSM,it is represented as a located net en-
tity. It refers to a linear location of the topology.
TrackSide Signal EULYNX The signal is an element of the track that sends a
message to the train. It can be physical i.e. a fixed
display element or non physical i.e. virtual or fic-
tive one.
KvbBalise EULYNX It is an object for train protection. Its position refers
to a “SpotLocation” such as a buffer-stop or point.
Figure 8: An example of a signal positioning in the railway
network using ATMO.
A NetEntity “Signal 45” object which represents
the functional object, it is associated to a the
railway network “FR Nord” (of type “Network”).
This signal includes:
A Location Object : SpotLocationCoordinate
named “Signal 45 Location” to represent its ge-
ometric footprint on the railway infrastructure,
which references two objects:
A PositioningSystem : LinearCoordinate Object
named “Signal 45 PK” to represent the precise
position in a linear frame of reference attached to
the LinearPositioningSystem topology
A Topology : LinearElement object named
“Track 1” to represent the portion of track to
which the signal is attached and which is part of
a topological element of the same nature but at a
higher level “Line 42”.
4 DISCUSSION
In this work, we have chosen a modular conceptu-
alisation of the railway on-board map. The differ-
ent modules developed corresponding to the domains
of the ontologies are then composed to constitute
the global ontology. This composition is achieved
through the existing links between the different mod-
ules which are : “Railway”, “Track”, “TrackSide” and
“Operational” (see figure 9).
Figure 9: Modules structuring.
The reasoning, inference and updating needs of
this model will be more simple thanks to the mod-
ularity. A reflection is currently underway to define
axioms and assess the global ontology. Indeed, qual-
ATMO: Autonomous Train Map Ontology
289
ity and correctness are the two important aspects con-
cerning heavyweight ontology evaluation. With these
perspectives in mind, we identified different metrics
to measure the ontology quality (computational effi-
ciency, adaptability and clarity) and the ontology cor-
rectness (accuracy, completeness, clarity, and consis-
tency) (Hlomani and Stacey, 2014).
Modularity also allows the re-usability of the on-
tology or of its modules. Indeed, we proposed a
framework to guarantee the safety of the autonomous
system from the upstream design phases thanks to the
use of ATMO and its alignment with the safety rules
(Chouchani et al., 2022).
5 CONCLUSIONS AND FUTURE
WORKS
In this work, we presented the methodological frame-
work adopted to develop ATMO the modular ontology
of on-board map of autonomous train. The main con-
tributions of this work are : (i) the use of standards
to provide a semantic map model ; (ii) the detailed
description of the ontology development methodol-
ogy METHONTOLOGY ; and (iii) the modularization
paradigm used to manage the complexity of the on-
tology.
knowledge acquisitions were explicit and implicit
by referring to bibliographic research, expert opinions
as well as national and international standards and
models. After a validation of the resulted lightweight
ontology, presented in the form of the UML model,
the ontology is sufficient enough to experiment with
reasoning and evaluate the heavyweight ontology.
The problem of building a modular ontology ap-
proached in this work, can serve as a basis for a reflec-
tion on the approach of developing an ontology of the
railway domain in general. Indeed, this proposal will
be discussed in future work within the framework of
the OntoRail project aiming to create a global dictio-
nary and to unify the vocabulary used by the various
international actors and standards like RSM, IFC and
EULYNX (OntoRail, 2022).
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