Modelling interlocking systems with UML

The aim of this project is to model a sample railway´s interlocking functionality according to a given set of written functional requirements. Once this has been done, the model will be gradually adapted to incorporate the requirements of other railways. Prior to starting the actual modelling work, a comprehensive database of railway functional requirements was compiled, in which every constituent condition associated with each requirement was indexed. Once this database reached a stable condition, the modelling was begun and its hierarchy has been closed based on that of the written requirements as closely as possible, in order to minimise inconsistencies. As the modelling progresses the written requirements themselves can also be improved by virtue of the clarifications arising from the process of modelling. A further advantage, especially given the linguistic mix of member of the Euro-Interlocking Project, is that the whole model can also be simulated in real time. This enables it to be checked against the actual functionality of the target system without constant reference to the natural language requirements or the inevitably somewhat complicated UML state diagrams. The long-term result of the project will be to establish a common core of pan-European requirements, to which national-specific functionality can then be added. It is hoped that this will greatly simplify the procurement process for the railways in the project.