Efficient data integration in the railway domain through an ontology-based methodology

The fragmented and ever more specialized nature of today’s railway systems makes it more and more complex to operate. An increasing number of actors are involved in the operation of a railway service. Infrastructure management is being separated from the operational aspect. Apart from the traditional state-owned train operators, open access and private operators start using the same infrastructure as well. Additionally, an increasing number of information systems, such as for real-time passenger information and entertainment need to exchange information. Therefore, Information & Communication Technologies have an increasingly vital role to play in the operation of the railways. However, as the use of stand-alone information systems improves the efficient operation of a single railway stakeholder, due to the complex fragmented nature, there is a clear need to integrate and correlate the available information. A high level of structured interoperability between information systems is required to correctly combine and manage this complex information. Several mechanisms exist to integrate information systems. The approach presented in this paper discusses the integration on data level. The main benefit of this approach is that it supports independent application development. It is after all undesirable and nearly impossible to centralise application development in world-wide fragmented and large systems, such as the railways. We will discuss a number of approaches towards data integration. Two main technologies are considered, namely Unified Modelling Language (UML) and ontologies. An ontology-based solution is compared with an UML-based approach. The advantages and disadvantages of both UML and ontology-based approaches are presented. The results are evaluated by means of a demonstrator developed as part of the InteGRail project (Intelligent Integration of Railway Systems), an FP6 EU research project. We believe that this demonstrator, the Network Statement Checker, is an ideal candidate to demonstrate the advantages of an ontology-based integrated information system. This tool allows the infrastructure operators to combine the network statements of different countries in different formats and to analyse them in a transparent way. The ontology-based approach shows clear advantages compared to the UML approach, by means of the formally defined model, but on the other hand the performance of the currently available tools is still to be improved. However, we believe that the augmented value of an ontology-based approach is also to be found in lower development costs because of its potential reuse in multiple applications, since their philosophy is to serve as a domain model instead of as a data model for a specific application.

Research highlights► The adoption of an ontology-based methodology abstracts information heterogeneity. ► Ontology-based information integration allows maintaining legacy systems. ► Validation through Network Statement Checker application shows promising results. ► The InteGRail approach has been validated and extended with description logics. ► A hybrid approach with common core vocabulary is preferred for the railway industry.