Baeten, Bergstra, and Klop (and later Caucal) have proved the remarkable result that bisimulation equivalence is decidable for irre-dundant context-free grammars. In this paper we provide a much simpler and much more direct proof of this result using a tableau decision method involving goal-directed rules. The decision procedure also provides the essential… (More)
The trace equivalence of BPP was shown to be undecidable by Hirshfeld. We show that all the preorders and equivalences except bisimulation in Glabbeek's linear time-branching time spectrum are undecidable for BPP. The results are obtained by extending Hirshfeld's encoding of Minsky machines into BPP. We also show that those preorders and equivalences are… (More)
A recent theorem 3, 7, 19] shows that strong bisimilarity is decidable for the class of normed BPA processes, which correspond to a class of context-free grammars generating the-free context-free languages. In 21] Huynh and Tian have shown that readiness and failure equivalence are undecidable for BPA processes. In this paper we examine all other… (More)
Within the past few years there has been renewed interest in the study of value-passing process calculi as a consequence of the emergence of the π-calculus. Here, [MPW89] have determined two variants of the notion of bisimulation, late and early bisimilarity. Most recently [San93] has proposed the new notion of open bisimulation equivalence. In this paper… (More)
The spi-calculus, proposed by Abadi and Gordon, is a process calculus based on the π-calculus and is intended for reasoning about the behaviour of cryptographic protocols. We consider the finite-control fragment of the spi-calculus, showing it to be Turing-powerful (a result which is joint work with Josva Kleist, Uwe Nestmann, and Björn Victor.) Next, we… (More)
We use some recent techniques from process algebra to draw several conclusions about the well studied class of ping-pong protocols introduced by Dolev and Yao. In particular we show that all nontriv-ial properties, including reachability and equivalence checking wrt. the whole van Glabbeek's spectrum, become undecidable for a very simple recursive extension… (More)
Over the past decade much attention has been devoted to the study of process calculi such as CCS Mil80, Mil89], ACP BK84, BK88] and CSP Hoa88] as the foundations of a mathematical model for nondeterminism and concurrency. Of particular interest has been the study of the behavioural semantics of these calculi as given by transition graphs arising from… (More)
The object calculus of Abadi and Cardelli AC96, AC94b, AC94a] is intended as model of central aspects of object-oriented programming languages. In this paper we encode the object calculus in the asyn-chronous-calculus without matching and investigate the properties of our encoding.