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Pipe-calculus: Difference between revisions
→Process calculus
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Implementations may include several of both categories and they are often open for extensions. | Implementations may include several of both categories and they are often open for extensions. | ||
In the literature it is a recurrent pattern that processes can be examined in two ways: one can combine component processes and examine the evolution of the resulting process. In this setting component processes may communicate with each other and the compound process may come to a rest without displaying external behavior. A single process can also be examined by placing it into a (usually not strictly specified) environment which is able to interact with the process. | |||
Pipe-calculus fits into this framework if we make the following observations. | Pipe-calculus fits into this framework if we make the following observations. | ||
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However there are notable differences. | However there are notable differences. | ||
Communication primitives in mainstream process calculi often unify two conceptual steps: the selection of a communication target (e.g. a channel or another process) and the act of message sending. The two steps are unseparable. Although one can introduce as a convention '''synchronization''' where the communicated message is ignored, and '''broadcast''' where a group of processes are waiting for messages on the same channel. | Communication primitives in mainstream process calculi often unify two conceptual steps: the selection of a communication target (e.g. a channel or another process) and the act of message sending. The two steps are unseparable. | ||
In pipe-calculus these steps are separated by design | For example [[wikipedia:pi-calculus|Π-calculus]] defines ''input prefixing'' <math>c\left(x\right).P</math> and ''output prefixing'' <math>\overline{c} \langle y \rangle.P</math> to denote receiving a name via channel <math>c</math> and sending a name via channel <math>c</math> respectively (communication primitives may occur in prefix form only). | ||
Although one can introduce as a convention '''synchronization''' where the communicated message is ignored, and '''broadcast''' where a group of processes are waiting for messages on the same channel. | |||
In pipe-calculus these steps are separated by design. | |||
In pipe-calculus there is no counterpart of '''hiding''' that prevents interference between two groups of processes that are using the same channel name for communication. Since there is no general, bidirectional parallel composition, we don't need a hiding primitive. The pipe operation naturally restricts communication to a pipeline. | In pipe-calculus there is no counterpart of '''hiding''' that prevents interference between two groups of processes that are using the same channel name for communication. Since there is no general, bidirectional parallel composition, we don't need a hiding primitive. The pipe operation naturally restricts communication to a pipeline. | ||
In pipe-calculus, if a process fails to synchronize, it is aborted. This is different from the usual implementation where a process that fails to synchronize | In pipe-calculus, if a process fails to synchronize, it is aborted. This is different from the usual implementation where a process that fails to synchronize does not evolve, it keeps "waiting" for a message. This semantics opens up the possibility for asynchronous communication. As a consequence, communication in pipe-calculus is inherently synchronous. | ||
== Notes == | == Notes == | ||