Showing papers in "Lecture Notes in Computer Science in 1987"

Petri nets in software engineering

Abstract: The central issue of this contribution is a methodology for the use of nets in practical systems design. We show how nets of channels and agencies allow for a continuous and systematic transition from informal and unprecise to precise and formal specifications. This development methodology leads to the representation of dynamic systems behaviour (using Pr/T-Nets) which is apt to rapid prototyping and formal correctness proofs.

Decidability of bisimulation equivalence for processes generating context-free languages

Abstract: A context-free grammar (CFG) in Greibach Normal Form coincides, in another notation, with a system of guarded recursion equations in Basic Process Algebra. Hence to each CFG a process can be assigned as solution, which has as its set of finite traces the context-free language (CFL) determined by that CFG. While the equality problem for CFL's is unsolvable, the equality problem for the processes determined by CFG's turns out to be solvable. Here equality on processes is given by a model of process graphs modulo bisimulation equivalence. The proof is given by displaying a periodic structure of the process graphs determined by CFG's. As a corollary of the periodicity a short proof of the solvability of the equivalence problem for simple context-free languages is given.

Automata and quantifier hierarchies

Abstract: The paper discusses results on ω-languages in a recursion theoretic framework which is adapted to the treatment of formal languages. We consider variants of the arithmetical hierarchy which are not based on the recursive sets but on sets defined in terms of finite automata. In particular, it is shown how the theorems of Buchi and McNaughton on regular ω-languages can be viewed as results on collapsing such quantifier hierarchies. Further automata theoretic hierarchies are outlined.

Security considerations in the design and implementation of a new DES chip

Abstract: This paper describes the impact of cryptographic requirements on the design of a new highly performant DES chip implementation. Actual cryptogaphical applications demand for both high security and high speed. It is the aim of this contribution to show how both can be combined.