In 6th NWPT, pages 428-443
Putting value passing into a calculus with sequential composition turns out to be more complicated than with a prefixing calculus. A semantics for such a calculus can be defined using environments, as in imperative languages.
Parallel processes have parallel environments, which can lead to ambiguity which of the environments shall be passed on to the sequentially following process. ACBS& solves this problem by distinguishing a foreground and a background process. The resulting operator can be interpreted as a fork operator, which ``forks off'' a background process.
The calculus is presented both in a ``pure'' and a value passing version, together with a complete axiomatisation for the pure calculus.
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