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- Hans Hüttel
- TACS
- 1994

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)

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 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)

- Hans Hüttel
- CAV
- 1991

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)

In Obliq, a lexically scoped, distributed, object-oriented programming language, object migration was suggested as the creation a copy of an object's state at the target site, followed by turning the object itself into an alias, also called surrogate, for the remote copy. We consider the creation of object surrogates as an abstraction of the above-mentioned… (More)

We present three modal logics for the spi-calculus and show that they capture strong versions of the environment sensitive bisimulation introduced by Boreale et al. Our logics differ from conventional modal logics for process calculi in that they allow us to describe the knowledge of an attacker directly.