Description is our business -- Concurrent processes as objects -- The Larch approach to specification -- Formal specification in metamorphic programming -- Formalizing design spaces: Implicit invocation mechanisms -- On type checking in VDM and related consistency issues -- Combining transformation and posit-and-prove in a VDM development -- A case for structured analysis/formal design -- A model-oriented method for algebraic specifications using COLD-1 as notation -- A mechanical formalization of several fairness notions -- Specification and stepwise development of communicating systems -- Writing operational semantics in Z: A structural approach -- EZ: A system for automatic prototyping of Z specifications -- Z and high level Petri nets -- An approach to the static semantics of VDM-SL -- Behavioural extension for CSP -- Cpo's do not form a cpo, and yet recursion works -- LPF and MPL? — A logical comparison of VDM SL and COLD-K -- Tactical tools for distributing VDM specifications -- An attempt to reason about shared-state concurrency in the style of VDM -- Reasoning about VDM specifications -- On formal specification of a proof tool -- Reasoning about VDM developments using the VDM support tool in mural -- EVES: An overview -- Deriving transitivity of VDM-reification in DEVA -- Upgrading the pre- and postcondition technique -- The formal development of a secure transaction mechanism -- Formal development of a Serial Copy Management System -- Specification and refinement in an integrated database application environment -- Techniques for partial specification and specification of switching systems -- Specification of the MAA standard in VDM -- Unintrusive ways to integrate formal specifications in practice -- An overview of HP-SL -- CICS project report experiences and results from the use of Z in IBM -- A debugger for a Meta-IV-like meta-language -- An executable subset of Meta-IV with loose specification -- Using VDM within an object-oriented framework -- The integrated software development and verification system ATES -- Using RAISE — first impressions from the LaCoS applications -- A specification of a complex programming language statement -- The prospectra system -- The visual presentation of VDM specifications -- Mural and specbox -- The VDM domain compiler a VDM class library generator -- The Delft VDM-SL front-end -- Prototyping with temporal VDM a status report -- The Exspect tool -- CADiZ - Computer aided design in Z -- The HP-ST toolset -- The RAISE toolset -- The IBM Z tool -- The VDM-SL editor and consistency checker -- B-tool -- A VDM subset compiler.

The proceedings of the fourth Vienna Development Method Symposium, VDM'91, are published here in two volumes. Previous VDM symposia were held in 1987 (LNCS 252), 1988 (LNCS 328), and 1990 (LNCS 428). The VDM symposia have been organized by VDM Europe, formed in 1985 as an advisory board sponsored by the Commission of the European Communities. The VDM Europe working group consisted of researchers, software engineers, and programmers, allinterested in promoting the industrial usage of formal methods for software development. The fourth VDM symposium presented not only VDM but also a large number of other methods for formal software development. Volume 1 contains conference contributions. It has four parts: contributions of invited speakers, papers, project reports, and tools demonstration abstracts. The emphasis is on methods and calculi for development, verification and verification tools support, experiences from doing developments, and the associated theoretical problems. Volume 2 contains four introductory tutorials (on LARCH, Refinement Calculus, VDM, and RAISE) and four advanced tutorials (on ABEL, PROSPECTRA, The B Method, and The Stack). They present a comprehensive account of the state of theart.