Graphics Programs Reference
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Figure 10.2: Translation rules for sequential constructs
3. Starting from the initial process, all process activation statements of
the type PAR A
1
,A
2
,...,A
n
are expanded with a copy of the GSPN
systems of the process schemas of A
1
,A
2
,...,A
n
. Since each A
i
can
activate other processes in the same manner, the substitution con-
tinues in depth-first mode until all the transitions that represent the
activation of a process have been replaced.
4. Pairs of communication transitions that belong to different processes
and that represent their (mutual) communication are fused to con-
cretely represent the synchronization deriving from the rendez-vous
protocol.
Let us now describe each single step in more detail.
Step 1 consists of generating the process schema. This task requires an ab-
straction phase that eliminates all the parts that are irrelevant with respect
to control. This can be a by-product of the compilation of the program,
or a specific compiler can be produced for this task, whose complexity is
substantially reduced, considering that many of the activities of a regular
compiler are of no interest in this setting.
Step 2 consists of producing a GSPN structure for each process schema.
The basic translation rules are shown in Fig.
10.2
(the sequential constructs),
process names, and τ indicates the translation function. Each process can
be characterized by a GSPN with one input place and one output place; the
same is true for any construct of our CSP-like applications.
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