• Lorenz Däubler, Michael Meyer zu Hörste, Gert Bikker, Eckehard Schnieder

Initial situation:

Because of the growing traffic density the European railway companies are anxious to adjust their control systems to one another, in order to accelerate the train movement over the national borders and to thus simplify the railway traffic. For this purpose an ETCS (European Train Control System) in being developed as a Europe-wide standard train control system. A formal specification of ETCS serves its conflict free and complete description and enables the use of formal concept methods (e.g. safety analysis, validation and others).

Aim:

Since only informal specifications for ETCS exist it was the aim to create formal specification based on the existing documents. For this the method of product data technology, according to ISO 10303 which is called STEP (Standard for the Exchange of Product Model Data) was used. STEP enables the platform independent exchange of product data and defines a generic product model that serves the description of products over the entire span of their lifes duration, independent of their implementation domain.

Solution:

In order to formalise the ETCS specifications, exemplary parts thereof were depicted on the product model of STEP. For this, the ARM (Application Reference Model) of the application log AP 212 (ISO 10303-212 electro technical design and installation), that serves the description of electro technical systems, instances and thus created product data, that corresponds with the ETCS specification.

Conclusion and outlook:

As a result corresponding product data was created that serves the formal description of functional and technical aspects of the equipment of ETCS. The description of signal and location related aspects and of function-product relationships (what device does what?) was impossible due to shortcomings in the ETCS documentation. Furthermore an implementation method of STEP was applied (ISO 10303-12, clear text encoding of the exchange structure) with enables the storing and the exchange of corresponding product data in the ASCII format (see picture). Further examinations concentrate on the possibilities for the specification of dynamic and behaviour logical aspects of ETCS, based on STEP.

Handout: Formal specifications of train control systems with STEP