Page 103 - 360.revista de Alta Velocidad - Nº 5

Test and Certification of Railway automation and digitalization approaches (Rail 4.0)

Figure 6:
Schema of a system with additional virtual internal interface as the specification view on the specific interface to be tested

Fig. 5 shows a schematic view of a system where the interface in focus is on the left, and is
shown with some detail. The specification addresses the functional level of the Rail Technical
Protocol (RTP) and abstract from the concrete implementation of communication through the
Rail Safe Transport Application (RaSTA) which utilizes an Ethernet connection. Fig. 6 gives the
specification view, where the additional virtual internal interface is added. Telegrams on the
focus interface are related to messages and observations on this virtual internal one. Technically,
these messages and observations are just actions of UML state machines which make up the
specification. They reflect actions happening on the other (masked) interfaces, but are not
formally related to them.
This works for the specification, but for testing it can of course not be done in terms of the
internal specification interface but needs the real behaviour on the masked interfaces. I.e., test
cases and operation have to take the view of Fig. 5, while their derivation must refer to Fig. 6.
The problem is acerbated by the unavailability of a precise relation between internal and masked
interfaces. In current practice, such a relation does not even exist: There are considerable
differences between the masked interfaces (whose standardisation is yet to be initiated) in the
different manufacturers' implementations of the devices as already mentioned above.

4.2 Solution Approach

Differences between the solutions of different manufacturers call for integrating them into
the test process in some way. Our solution relies on the assumed ability of the manufacturers
of bridging the gap between (virtual) internal messages and commands and externals. The
envisaged test architecture is depicted in Fig. 7.

Figure 7: Components of the test architecture.

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 101