Semantics of Specification Languages (SoSL): Proceedings of the International Workshop on Semantics of Specification Languages, Utrecht, The Netherlands, 25 – 27 October 1993

366 Pages·1994·13.936 MB·

by  Stephen Brien (auth.), D. J. Andrews, J. F. Groote, C. A. Middelburg (eds.)

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continued on back page ...
D.J. Andrews, J.F. Groote and C.A. Middelburg (Eds.)
Semantics of Specification
Languages (SoSL)
Proceedings of the International
Workshop on Semantics of Specification
Languages, Utrecht, The Netherlands,
25-27 October 1993
•
Published in collaboration with the
British Computer Society
Springer-Verlag
London Berlin Heidelberg New York
Paris Tokyo Hong Kong
Universiteit
Barcelona Budapest
Utrecht
OJ. Andrews
Department of Mathematics and Computer Science
University of Leicester, University Road
Leicester, LEI 7RH, UK
J.F. Groote, drjr
C.A. Middelburg, prof.drjr
Department of Philosophy
Utrecht University
Heidelberglaan 8, 3584 CS Utrecht
The Netherlands
ISBN-13:978-3-540-19854-3 e-ISBN-13:978-I-4471-3229-5
DOl: 10.1007/978-1-4471-3229-5
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Preface
SoSL was the first International Workshop on Semantics of Specification
Languages, held from 25-27 October 1993 in Utrecht, the Netherlands.
The workshop was organized by the Department of Philosophy of Utrecht
University with financial support from the Nationale Faciliteit Informatica
of the Nederlandse Organisatie voor Wetenschappelijk Onderzoek
(NWO), and under the auspices of the British Computer Society'S
specialist group in Formal Aspects of Computing Science (BCS FACS).
The concern of the workshop was the semantics of specification
languages, and the issues closely related to this area, such as type
checking and the justification of proof rules and proof obligations. Its
aim was the exchange of problems and ideas in this field of formal
methods, and the identification of common programs of work for further
investigation.
The program of SoSL consisted of 3 invited lectures presenting the
developments of the semantics of 3 major specification languages.
Furthermore, there were 16 presentations of submitted papers. This
volume provides a direct account of the workshop. It contains 3 papers
that match the invited lectures and the 16 selected papers.
The editors want to thank all those who have contributed to the
workshop; the Program Committee and the referees for selecting the
contributed papers, the invited speakers for their interesting talks, the
Organizing Committee for all their efforts, and of course the participants.
We have the feeling that the workshop was worthwhile and should be
repeated.
Utrecht, November 1993 The Editors
Invited Speakers:
Stephen Brien, Oxford University (Z)
Loe Feijs, Philips Research Laboratories Eindhoven (COLD)
Robert Milne, BNR Europe (RSL)
Program Committee:
Derek Andrews, University of Leicester (chair)
Jan Bergstra, University of Amsterdam, Utrecht University
vi Preface
George Leih, PTT Research
Brian Monahan, University of Manchester
Hans Toetenel, Delft University of Technology
Jean Goubault, Bull Corporate Research Centre
Jim Woodcock, Oxford University
Organizing Committee
Annemarie Besselink, Utrecht University
Jan Friso Groote, Utrecht University
Kees Middelburg, PTT Research, Utrecht University (chair)
Rick Thomas, University of Leicester
Contents
The Development of Z
S. Brien ................................................................................................... 1
An Overview of the Development of COLD
L.M.G. Feijs ......................................................................................... 15
The Formal Basis for the RAISE Specification Language
R. Milne ................................................................................................ 23
The Static Part of the Design Language COLD-K
G.R. Renardel de Lavalette ................................................................. 51
Generation of Proof Obligations for Type Consistency
(Extended Abstract)
F.M. Damm and B.S. Hansell.............................................................. 83
Experiences in Developing a Proof Theory for VDM
Specifications
l.S. Fitzgerald and R. Moore ............................................................ 101
Towards Proof Rules for Looseness in Explicit Definitions from
VDM-SL
P.G. Larsen ........................................................................................ 118
Loose Real-Time Communicating Agents
H. Toetenel......................................................................................... 135
A Timed Specification Language for Concurrent Reactive
Systems
M. Schenke ......................................................................................... 152
Multiparadigm Specification Languages: A First Attempt at
Foundations
E. Astesiano and M. Cerioli ........ .................. .................................... 168
The Semantics of Extended ML: A Gentle Introduction
S. Kahrs, D. Sannella and A. Tarlecki ............................................. 186
Type-Checking Revisited: Modular Error-Handling
T.B. Dinesh......................................................................................... 216
Proof Theory for ,uCRL: A Language for Processes with Data
l.F. Groote and A. Ponse .................................................................. 232
viii Contents
Case Study: Stepwise Development of a Communication
Processor Using Trace Logic
S. Kleuker .................................................... ....................................... 252
Rendez-vous with Bundle Event Structures
B. Botma ............................................................................................. 270
Syntactic Action Refinement in Presence of Multiway
Synchronization
D.-E. Saiaouni and J.-P. Courtiat .................................................... 289
From Implicit via Inductive to Explicit Definitions
G.R. Renardel de Lavalette ............................................................... 304
Verifying Process Algebra Proofs in Type Theory
M.P.A. Sellink .................................................................................... 315
Reasoning About Dynamic Features in Specification Languages
A Modal View on Creation and Modification
R. Groenboom and G.R. Renardel de Lavalette .............................. 340
Author Index .................................................................................... 357
The Development of Z
Stephen Brien
Programming Research Group, Oxford University
Abstract
Z is a model-oriented specification language, which originated in the
early 1980s. The first description by Abrial included a structuring mecha
nism called a class, which was very similar to a schema (i.e. a combination
of a declaration and a constraining predicate). The Z style has developed
as a result of tackling practical examples and adapting the notation to
their needs; this has resulted in a style and notation that is widely appli
cable to the description of certain kinds of computer system, particularly
the client-server model.
With the publication of Sufrin's Z Handbook the development and
understanding of Z had progressed. A type inference system and rules
for reasoning were provided and the notions of schemas and generic types
had evolved into their now familiar form. The first formal semantics was
given by Spivey using a variety-based denotational semantics where the
metalanguage used was Z itself, and included a brief sketch of a possible
proof theory.
The standardisation process for Z provided a powerful motivation to
attempt this exercise again. The standard semantics uses a relational
approach, and attempts a loose definition of the meaning of undefined
elements so as to accommodate some of the different possible treatments
while ensuring that the logic is two-valued. This paper traces the evo
lution of the semantics of Z from the early efforts to the definition in
the Z standard, comparing the various approaches to defining the model,
presenting the semantics and dealing with undefinedness.
1 The Early Days
The origins of the development of Z can be traced back to the Software Engi
neering Project at the Programming Research Group in Oxford. This project
started in 1978 with both Tony Hoare and Bernard Sufrin associated with it
from the beginning. It was the first of many projects which supported re
searchers engaged in work on specification. At around the same time Jean
Raymond Abrial was giving lectures on specification at Queen's University
Belfast. The language was based on three principles: a strict formalism, recog
nition of set theory as a sound basis, and the necessity of a strong structur
ing mechanism. These course notes were published with Steve Schumann and
Bertrand Meyer in a paper simply called "Specification Language" [4].
2
In late 1979 Abrial moved to Oxford. He presented a seminar course to re
search staff and students on his specification language. This language included
schema-like objects called classes which were a combination of declarations and
a constraining predicates:
class (1)
a :Xj
b: Y
where
p
end
Notably, there were no semantics for this language. Rod Burstall observed at
the time that the language had a strong flavour of "Bourbaki" . .
In 1980 Abrial produced two papers on Z [1, 2] a Basic Library and a Syntax
and "Semantics". The basic library was a series of chapters of Z specifications
of sets, functions, relations and other mathematical structures. This was an
early forerunner of the mathematical toolkit which was published in Spivey's
Reference Manual [42]. The syntax and semantics paper included an outline
proof system for the mathematical sublanguage, which lay somewhat neglected
for many years.
Soon afterwards Abrial, Sorensen and Clement started a project suggested
by Bernie Cohen, then of STL, to formally specify and implement CAVIAR
(Computer Aided Visitor Information and Reception) System [14].
During this project the notation underwent a redesign and the notion of
a class conjunction was introduced. The notation that resulted from this re
working was essentially the same as the current mathematical language of Z,
however the concrete notation used keywords. For example, the definition of
set union was as follows:
op(U) = In Sl, S2 -+ S3 then (2)
=
S3 set X whereX E SI or X E S2 end endj
The style reverted to a more familiar notation "under the impact" of Dana
Scott's verdict that it was too verbose. Although there was some form of generic
definition, there was no formal type system and only an informal semantics.
Impetus for the further development of schemas came from the realisation
that the standard mathematical forms of extending states and promoting op
erations on them were too unwieldy for use in the specification of large scale
systems. Experience in VDM[26, 25], influenced by the presence of in the PRG
of Cliff Jones, suggested that what was needed was a formalism in which ex
tension and promotion were simply expressible, and for which proof rules could
be given directly.
These efforts produced the nucleus of what later became known as the
schema calculus. Generated mostly from problems encountered in defining