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10.2. Data and Control Flows in ETCS Modes
10.2.2. Stand By Mode
Stand By cannot be entered directly by the driver but only by a transition from No Power. The
provided functionality is the enforcement of the stand-still of the train and the data collection
for the train mission [90, pp. 8-17].
Application Level 0
The data collected from the driver for the train mission is used to determine the next ETCS
Mode and, if necessary, an Application Level switch. Figure 10.4 represents the model of the
data flow in Application Level 0. According to the transition matrix in Figure 10.1, all guard
objects are used besides “c13-p3”, which is executed in the case of an error, because the error
oModeGuard object is a property of the graph itself.
The primary functionality is modelled in three oSubFunction objects: “Start of Mission in
Stand By”, “Stand Still Supervision”, and “DMI Stand By”.
The “Start of Mission in Stand By” function collects, according to [90, pp. 8-17], data from
the driver. In the model, the sub-function only holds an oEmbeddedStateMachine object with
a Boolean true input to start it. Due to its simplicity, it is omitted in the documentation,
and only the related gEmbeddedStateMachine graph is shown in Figure 10.5. States that are
prefixed with a “D” or “S” and are followed by a number are directly transferred from the
so-called state diagram in [90, p. 18]. Since the state diagram syntax in the SRS is a mixture
of states, activities, executions, and decisions, not all of them can be mapped directly to the
openETCS model.
It should be remarked that the used state diagram formalism in the SRS was not integrated
in the openETCS meta model because first it is a mixture of already existing diagram types, like
state machines / diagrams [80] and (UML) activity diagrams [64]. Second, the used formalism
for control structure must be combinable with data flows, which was discussed and explained
in Section 7.2. This is not the case for the state diagram syntax used in the SRS.
State ”S1: Request Driver ID“ is the initial state, which is executed until the driver has
entered his or her ID in the DMI.
”D1: Check ETCS Level“ verifies if the current ETCS Application Level is valid or not.
State ”S2: Request ETCS Level“ waits for the input of the current Application Level via the
DMI if the Application Level is invalid.
In ”Check Train Position“, the driver can revalidate the current train position or enter a new
one.
”S10: Waiting for Driver Selection” offers the driver via the DMI the selection of overriding
an existing EoA 1 or the proceeding one with an active mission or the entering of train
data.
“Override EoA” is a final state, in which the transition to the Staff Responsible Mode is
activated via the “c37” condition with the usage of the “Staff Responsible via Override”
oVariableStorage object. Since the Staff Responsible Mode is only available in ETCS
1 End of Authority
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