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7.3. Concrete Syntax for Graph Bindings
NP SB · · ·
NP c4-p2 · · ·
SB c29-p2 · · ·
. . .
. ..
Figure 7.5.: Simple example for a gEVCStateMachine matrix
7.3.2. gMainFunctionBlock and gSubFunctionBlock Graph Types
Main function blocks are used to model transformations of the data flow performed by the EVC
in a specific Mode and ETCS Application Level (Figure 7.6). Since these transformations may
be quite extensive, gMainFunctionBlock graphs may contain oSubFunction objects allowing
top-down decomposition into gSubFunctionBlock graphs. The behavioural interpretation is the
same as if all details occurring in the lower-level function block had been presented already in
the original function block without referencing an oSubFunction object.
Objects in the gMainFunctionBlock and gSubFunctionBlock graph type can be related
by the binary DataFlow relationships connecting objects by means of a DataOutput role
(sending object) and a DataInput role (receiving object). The possibility to connect general
objects by means of data flows and ports enables the specification of feed-forward or feed-back
structures [30], which are typically used in loop controllers. The GOPPRR port concept is used
to avoid modelling errors and facilitates the checking of static model semantics with respect to
interface consistency.
Compared to other graph types, both function block types use the majority of object types
in the meta model because they mainly describe the complete functionality in a certain ETCS
Application Level. Those object types can be divided in four categories:
sources
sinks
transformations
storages
specials
Object types that only provide outputs. Those are mostly related to sensor
devices, like odometers. All types in this category use oFunctionBlockOut
as super type.
Object types that only have inputs. Those are mostly related to actuator
devices, like service brakes. All types in this category use oFunctionBlockIn
as super type.
Object types with inputs and outputs. Those apply a certain transformation
on the inputs and give the results on the output. For example, the
computation of a braking-curve or the simple calculation of a sum. All types
in this category use oFunctionBlockIn as super type.
Object types for storing and restoring data values. No super type is used
for storages.
Object types that do not have any inputs and outputs and are not a direct
part of a data flow. No super type is used for special object types.
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