Abstract
For sequential programming, the theory of functions provides a uniform metalanguage to describe behaviours by abstracting from the actual implementation of programs. For concurrent and distributed systems, instead, there is no well accepted metalanguage to describe the possible observations of the behaviour of programs. The proper treatment of observations is thus an important and complex issue of concurrency theory. In this paper we show that observations can be described in a uniform way by introducing certain algebras called observation algebras. They lift to an algebraic level the standard treatment of actions in the operational semantics of process algebras. Observations are described as terms of an algebra. As a consequence, we separate the control level (the operational semantics) from the data level (the observations). The chosen notion of observability can be obtained by suitably axiomatizing the operations of the observation algebra. We show how observation algebras can be naturally derived from process algebras. As a case study we consider Milner's CCS. We introduce an observation algebra for CCS and we show that the standard interleaving semantics can be obtained by axiomatizing the operations to yield actions. Furthermore, we give a complete axiomatization of an observation algebra whose elements are certain labelled partial orderings of events (pomsets) called Spatial Pomsets.
Work partially supported by ESPRIT Basic Research Action 3011, CEDISYS, and by Progetto Finalizzato Informatica e Calcolo Parallelo, obiettivo LAMBRUSCO.
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Ferrari, G.L., Montanari, U. (1991). The observation algebra of spatial pomsets. In: Baeten, J.C.M., Groote, J.F. (eds) CONCUR '91. CONCUR 1991. Lecture Notes in Computer Science, vol 527. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-54430-5_89
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DOI: https://doi.org/10.1007/3-540-54430-5_89
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