Abstract not found

The main ideas underlying work on the model-theoretic foundations of algebraic specification and formal program development are presented in an informal way. An attempt is made to offer an overall view, rather than new results, and to focus on the basic motivation behind the technicalities presented elsewhere.

A formal methodology is presented for the systematic evolution of modular Standard ML programs from specifications by means of verified refinement steps, in the framework of the Extended ML specification language. Program development proceeds via a sequence of design (modular decomposition), coding and refinement steps. For each of these three kinds of steps, conditions are given which ensure the correctness of the result. These conditions seem to be as weak as possible under the constraint of being expressible as "local" interface matching requirements. Interfaces are only required to match up to behavioural equivalence, which is seen as vital to the use of data abstraction in program development. Copyright c fl 1989 by D. Sannella and A. Tarlecki. All rights reserved. An extended abstract of this paper will appear in Proc. Colloq. on Current Issues in Programming Languages, Joint Conf. on Theory and Practice of Software Development (TAPSOFT), Barcelona, Springer LNCS (1989)....

In this paper, we motivate and present a data model for conceptual design of structural and behavioural aspects of databases. We follow an object centered design paradigm in the spirit of semantic data models. The specification of structural aspects is divided into modelling of object structures and modelling of data types used for describing object properties. The specification of object structures is based on an Extended Entity--Relationship (EER) model. The specification of behavioural aspects is divided into the modelling of admissible database state evolutions by means of temporal integrity constraints and the formulation of database (trans)actions. The central link for integrating these design components is a descriptive logic-- based query language for the EER model. The logic part of this language is the basis for static constraints and descriptive action specifications by means of pre- and postconditions. A temporal extension of this logic is the specification language for tem...

T ROLL is a language to specify information systems with dynamic behavior. Here, we elaborate on the specification of object aggregation in T ROLL . We distinguish between two kinds of aggregation, static and dynamic aggregation. Static aggregation means that the composition of objects is described using predicates over constant properties. Dynamic aggregation means that we may alter the composition of objects by invoking special operations (events) that are implicitly defined for each dynamic complex object. Additionally, we describe the specification of disjoint complex as a means for structuring a specification. We introduce language features to describe object aggregation and give some hints towards their semantics. 1 Introduction The first steps in an object-oriented approach to information system development concentrate on the abstract description of the relevant static and dynamic aspects of real-world objects (the Universe of Discourse, UoD) [Gri82, RBP + 90, Boo90] (concept...

One of the most novel features of Casl, the Common Algebraic Specification Language, is the provision of so-called architectural specifications for describing the modular structure of software systems. A brief discussion of refinement of Casl specifications provides the setting for a presentation of the rationale behind architectural specifications. This is followed by some details of the features provided in Casl for architectural specifications, hints concerning their semantics, and simple results justifying their usefulness in the development process.

This document reports the general theory of specification systems from the point of view of GDM. GDM is the acronym for "Gda'nsk Development Method". It is the name of a project run in the Institute of Computer Science of the Polish Academy of Sciences and in the University of Gda'nsk, with the support of the Polish Committee for Scientific Research and of the EEC programme CRIT. The aim of the project is to set up a framework for a uniform treatment of specification styles encountered in various branches of modern computer science. In the literature to date, a number of formalisms have been proposed with the common aim to describe a planned behaviour of a program, of a data base, or of a piece of hardware. Prominent examples are:

The way that refinement of individual "local" components of a specification relates to development of a "global" system from a specification of requirements is explored. Observational interpretation of specifications and refinements add expressive power and flexibility while bringing in some subtle problems. The results are instantiated in the context of Casl architectural specifications.

A specification formalism with parameterisation of an arbitrary order is presented. It is given a denotational-style semantics, accompanied by an inference system for proving that an object satisfies a specification. The inference system incorporates, but is not limited to, a clearly identified type-checking component. Special effort is made to carefully distinguish between parameterised specifications, which denote functions yielding classes of objects, and specifications of parameterised objects, which denote classes of functions yielding objects. To deal with both of these in a uniform framework, it was convenient to view specifications, which specify objects, as objects themselves, and to introduce a notion of a specification of specifications. The formalism includes the basic specification-building operations of the ASL specification language. This choice, however, is orthogonal to the new ideas presented. The formalism is also institution-independent, although this iss...

. Various formalizations of the concept of "refinement step" as used in the formal development of programs from algebraic specifications are presented and compared. 1 Introduction Algebraic specification aims to provide a formal basis to support the systematic development of correct programs from specifications by means of verified refinement steps. Obviously, a central piece of the puzzle is how best to formalize concepts like "specification", "program" and "refinement step". Answers are required that are simple, elegant and general and which enjoy useful properties, while at the same time taking proper account of the needs of practice. Here I will concentrate on the last of these concepts, but first I need to deal with the other two. For "program", I take the usual approach of algebraic specification whereby programs are modelled as many-sorted algebras consisting of a collection of sets of data values together with functions over those sets. This level of abstraction is commens...