30 lines
No EOL
1.3 KiB
Markdown
30 lines
No EOL
1.3 KiB
Markdown
- Up to now, we have considered non-deterministic processes
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- Two main features are missing for modeling a concurrent system:
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- Simultaneous execution of processes
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- Inter-process interaction
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- Solutions adopted:
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- Parallel composition, with interleaving semantics
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- Producer/consumer paradigm
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Given a set of names N (that denote events)
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- a (∈ N) denotes consumption of event a
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- $\bar{a}$ (for a ∈ N) denotes production of event a
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- a and $\bar{a}$ are complementary actions: they let two parallel processes synchronize on the event a
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When two processes synchronize, an external observer has no way of understanding what is happening in the system
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- synchronization is not observable from the outside; it produces a special ‘silent’ action, that we denote with τ
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The set of actions we shall consider is: 
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It is also useful to force some processes of the system to synchronize between them (without the possibility of showing to the outside some actions)
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The restriction operator P\a restricts the scope of name a to process P (a is visible only from within P)
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This is similar to local variables in a procedure of an imperative program
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fino alla 7 compresa... |