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10
openETCS Model
The openETCS model or rather, according to Figure 7.1, the openETCS formal specification is
the CIM of the case study. As already discussed in Section 7.1, the modelling of the complete
ETCS specification would exceed the limits of this work and this case study by far. Therefore,
only a sub-subset of the ETCS SRS is modelled here. Nevertheless, the limitation to certain
ETCS Modes and Application Levels emerged to be not sufficient to gain an openETCS model
that is small enough to be manageable in this dissertation. Hence, not all functionality specified
in the SRS for the used ETCS Modes is modelled. The main goal of the openETCS model is
to give an example that is executable in a simple but adequate simulation environment. This
simulation is described in Chapter 11. The reduction of used functionality is mainly related to
the modelling of data flows.
It should be noted that parts of the SRS that are not modelled for the case study are not
always emphasised in this document since ETCS is primarily used as an example of a train
control system. Another certain remark is that not all parts of the model are presented in
this chapter because those are mostly graphs, which all together would require extensive space.
The complete model can be found in Appendix C.
This chapter presents exemplary diagrams of the openETCS model in the order of the
top-down structure of the meta model graph types in Figure 7.2. The description starts with
the so-called root graph for the ETCS Modes and transitions, which is followed by data and
control flows for each combination of ETCS Mode and Application Level. Afterwards, the
extraction of data from incoming balise telegrams is described and the models of the used
ETCS language elements are presented. Finally, possible concepts of extending models in
respect to safety properties are discussed.
10.1. ETCS Mode and Transition Matrix
Although the GOPRR or GOPPRR meta meta model does not define or require a certain root
graph, the gEVCStateMachine graph type can be interpreted as such because it must exist
exactly once in an openETCS meta model (see Subsection 7.5.1) and all other graph instances
are connected with it via decompositions and explosions (see Section 7.2). The modelled
transition matrix of the used ETCS Modes (compare Section 7.1) is shown in Figure 10.1.
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