Abstract
We study the equational theory of Timed CCS as proposed by Wang Yi in CONCUR’90. Common to Wang Yi’s paper, we particularly focus on a class of linearly-ordered time domains exemplified by the positive real or rational numbers. We show that, even when the set of basic actions is a singleton, there are parallel Timed CCS processes that do not have any sequential equivalent and thus improve on the Gap Theorem for Timed CCS presented by Godskesen and Larsen in FSTTCS’92. Furthermore, we show that timed bisimilarity is not finitely based both for single-sorted and two-sorted presentations of Timed CCS. We further strengthen this result by showing that, unlike in some other process algebras, adding the untimed or the timed left-merge operator to the syntax and semantics of Timed CCS does not solve the axiomatizability problem.
The work of the authors has been partially supported by the project “The Equational Logic of Parallel Processes” (nr. 060013021) of The Icelandic Research Fund.
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Aceto, L., Ingólfsdóttir, A., Mousavi, M. (2007). Impossibility Results for the Equational Theory of Timed CCS. In: Mossakowski, T., Montanari, U., Haveraaen, M. (eds) Algebra and Coalgebra in Computer Science. CALCO 2007. Lecture Notes in Computer Science, vol 4624. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-73859-6_6
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