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Process → Substeps |
The behaviour of a process is given by a set of substeps which
are executed endlessly in a loop.
Each substep is specified by an java statement. Any valid java statement
can be declared as a substep. In addition to the simple statements you can also declare
complex statements like for-, while- and if-statements. Figure 12 shows for example
the substeps of a process.
Figure 12
There are two different kinds of substeps. For an initialisation phase you can specify a series of
initial substeps. These initial substeps are executed once at the beginning of the execution.
Besides the initial substeps, the
loop substeps exist. The loop substeps are executed after the execution of the initial substeps.
They are executed in a loop repeatedly.
During the visualisation the simulation of time is realised by
time steps. For this a number of time steps is assigned to each substep of a process.
This number of time steps represent the time in which the substep has been executed.
Within this training module a time step is the elementary time unit and can not
be split into smaller units. It is an abstract among of time and you can interpret it as
seconds or minutes depending on the context of your process network example.
The stepwise visualisation which is described late in this introduction is also based on
these time steps. For more details see chapter
Visualisation.
For the sending and receiving of data two additional commands send and wait
exist. These commands are not included in the standard java language specification.
With the command send a process can send an integer value to another process.
The statement send i to X for example
sends the value of the local variable
i via the FIFO buffer
X to another process.
Instead of the variable i you can also specify an integer constant
like send 2 to X.
With the command wait integer values can
be received from another process. The statement
i = wait Y for example reads a value from the FIFO buffer
Y and assigns the value to the local variable i. If the FIFO buffer Y
is empty, the process has to wait in this substep until the buffer contains new data.
The variables which you use in the substeps are local to the
process. They are declared by assigning a value to them
in a substep. Figure 12 shows for example that the boolean variable b has
been initialised with the value true in an initial substep. Later it can be
used in a loop substep (see Figure 12 if-statement).
In the following subsection you will see how you can add, move and remove a process in the network editor.
Introduction > Process
> Substeps
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