Editing Process calculus (section)

=== Hiding ===
Processes do not limit the number of connections that can be made at a given interaction point. But interaction points allow interference (i.e. interaction). For the
synthesis of compact, minimal and compositional systems, the ability to restrict interference is crucial. ''Hiding'' operations allow control of the connections made between interaction points when composing
agents in parallel. Hiding can be denoted in a variety of ways. For example, in the [[π-calculus]] the hiding of a name <math>\mathit{x}</math> in <math>\mathit{P}</math> can be expressed as <math>(\nu\; x)P</math>, while in [[Communicating sequential processes|CSP]] it might be written as <math>P \setminus \{x\}</math>.
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(Commented out because "Figure" is missing - can the Figure be added?)
Figure shows the effect of going from ''P'' to (''ν'' ''x'')''P''.  The process ''P'' on the left can interact with the outside world on ''x'', ''y'' and ''z''. In contrast, (''ν'' ''x'')''P'' on the right can only use ''y'' and ''z'' for this purpose. The restriction does not prevent usage of ''x'' inside ''P''. But what happens if ''x'' gets sent to a process outside of (''ν'' ''x'')''P'', as may happen in (''ν'' ''x'')(''y''<''x''> | ''Q''), provided ''x'' \neq ''y''?  Whether or not it is possible to communicate a name hidden this way is another important point of divergence between different calculi.
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