Luca Aceto, Anna Ingolfsdottir, MohammadReza Mousavi Proceedings of the 2nd Conference on Algebra and Coalgebra in Computer Science (CALCO'07), Bergen, Norway, volume 4624 of Lecture Notes in Computer Science, pages 80--95, Springer-Verlag, August 2007.
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 domain 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.
(Paper in .ps format in .pdf format) (A Presentation in .pdf format)@InProceedings{MousaviCALCO07,
author = "Aceto, Luca and Ingolfsdottir, Anna and Mousavi, MohammadReza",
title = "Impossibility Results for the Equational Theory of Timed CCS",
booktitle = "Proceedings of the Proceedings of the 2nd Conference on Algebra and Coalgebra in Computer Science",
volume = "4624",
pages = "80--95",
series = "Lecture Notes in Computer Science",
address = "Bergen, Norway",
publisher = "Springer-Verlag, Berlin, Germany",
year = "2007"
}