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7.3. Concrete Syntax for Graph Bindings
7.3.3. gEmbeddedStateMachine Graph Type
The gEmbeddedStateMachine graph type syntax is similar to the gEVCStateMachine, but
is also used, as the gMainFunctionBlock and gSubFunctionBlock graph types, to define the
functionality or rather the behaviour in a certain EVC Mode. In contrast to those graph types
that are used to model data flows, this graph type is used to specify control flows. Experience
with system modelling shows that the specification of data flows alone is insufficient in most
cases because a separate means for modelling control is needed [8]. For example, to model
communication protocols. The syntax definition of the gEmbeddedStateMachine graph type is
shown in Figure 7.8, which only differs from Figure 7.3 in the object type used for states. Of
gEmbeddedStateMachine
InitialTransition
StateTransition
CurrentState
1...1
NextState
1...1
CurrentState
1...1
NextState
1...1
oEmbeddedInitialState
1...1
oEmbeddedState
1...1
oEmbeddedState
1...*
oEmbeddedFinalState
1...*
Figure 7.8.: gEmbeddedStateMachine binding syntax
course, it is also meaningful to present instances of gEmbeddedStateMachine as matrix as for
gEVCStateMachine, but for a smaller amount of states the “normal” graphical representation
might provide the same or even better abstraction. Therefore, the representation kind for this
graph type can be chosen accordingly to the concrete state machine to be modelled.
7.3.4. gCommunicationSender Graph Type
The purpose of gCommunicationSender graphs is to compose telegrams with data from gFunctionBlock
graphs and to transmit them via a communication device. Currently, for this case
study, only Eurobalises [84] are used. The object types they operate on are oTelegram, oPacket,
oVariableInstace, oVariableStorage, and the different devices types for transmission. To model
or specify operations on an oTelegram, an oVariableStorage object can be connected by a
DataFlow relationship with an oVariableInstance object. Composition of gPacket objects by
oVariableInstance objects is modelled by graphical containment. The same is done for the
composition of oTelegram objects. Composed oTelegram objects can also be connected by a
DataFlow relationship with a certain sending device to specify the transmission of a telegram.
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