Ian C. Morrey

Towards quality requirements via animated formal specifications

Assuring a high quality requirements specification document involves both an early validation process and an increased level of participation. An approach and its supporting environment which combines the benefits of a formal system specification and its subsequent execution via a rapid prototype is reported. The environment assists in the construction, clarification, validation and visualisation of a formal specification. An illustrative case study demonstrates the consequences of assertions about system properties at this early stage of software development. Our approach involves the pragmatic combination of technical benefits of formal systems engineering based techniques with the context‐sensitive notions of increased participation of both developer and user stakeholders to move us closer towards a quality requirements specification document.

A toolset to support the construction and animation of formal specifications

Abstract Model-based specification languages, in particular Z, have been widely used to provide a precise and unambiguous statement of the proposed system as perceived by the developer. However, for many complex specifications, developers cannot themselves be sure about the “intended behaviour” of the specification constructed. This paper reports on an approach and toolset that enables a developer to construct a Z specification using the wiZe editor, demonstrate its properties by transforming it into an executable form using the ZAL animation system, and explore its adequacy by animating a variety of scenarios. The application of the approach and toolset is demonstrated on a specification of a telephone network to illustrate that specification validation could be carried out incrementally during development through investigative scenarios to assess the adequacy of the specification. It is claimed that this interaction, when used in peer review or by the individual developer, can provide enhanced accessibility, a better understood and possibly an improved specification.

Towards a system for the construction, clarification, discovery and formalisation of requirements

Requirements engineering is fraught with possibilities for misunderstanding and mistakes and it is well known that the earlier such errors occur in the lifecycle the more costly the consequences. Formal specifications provide from a developers perspective a clear, concise and unambiguous statement of the system requirements. Prototyping enables effective user participation in the validation of requirements The authors report on work towards a system that judiciously combines the strengths of formal specification and prototyping to assist in the construction, negotiation, clarification, discovery and formalisation of requirements that could make the crucial activity of requirements engineering less problematic.<<ETX>>

Use of a specification construction and animation tool to teach formal methods

ZAL (Z Animation in LISP) is a package which allows a Z specification to be incrementally designed and validated in an interactive environment built on Common LISP. A Z specification is transformed into an equivalent ZAL program which can be executed in order to demonstrate the functionality of the intended implementation. ZED is a full screen editor and syntax analyser for Z. Using these two tools as an integrated package encourages and facilitates an exploratory approach to formal specification which reflects the way in which many users of Z (particularly beginners) prefer to approach the specification task. The package has also been used to support the teaching of students following courses in discrete mathematics, formal specification and software development.<<ETX>>

Visualisation of Executable Formal Specifications for User Validation

This paper reports on research work to facilitate the user validation process in an application-orientated fashion based on executable formal specifications. It is part of an ongoing effort to move towards quality requirements via graphical visualisations of formal specifications. It builds upon previous work that supports the animation of Z specifications in a LISP-based environment called ZAL (Z Animation in LISP). In addition, it embodies a visualisation system called ViZ (Visualisation in Z) which enables the comprehension, clarification and validation of executable formal specification notations. Technology provided by ViZ allows software developers to choose an appropriate representation of objects used in an executable formal specification and create dynamic and/or static animations of these objects in an interactive and iterative fashion. ViZ provides a generic visualisation model to capture the process of visualising static and dynamic behaviour of a ZAL specification. This paper outlines our approach, details ViZ and illustrates its application in a real-world setting.

Towards CASE tools for prototyping Z specifications

A project that aims to develop an animation environment for a formal specification is described. Two CASE tools, one for constructing (i.e., inputing, editing and syntax checking) a formal specification, and the other for executing a formal specification, are described. A case study is used to illustrate the transformation process required to construct a prototype which can be executed to validate requirements and explore their consequences. The feasibility of translating and executing formal specifications is discussed and directions for future work are presented.

Requirements validation based on the visualisation of executable formal specifications

This paper reports on ongoing research work to facilitate the user validation process based on executable formal specifications. It embodies a visualisation system which allows software developers to choose an appropriate representation of objects used in a formal specification and create a dynamic and/or static animation of these objects in an interactive and iterative fashion. This paper outlines our approach and illustrates its application in a real-world setting.

Grammatical Inference Techniques and Their Application in Ground Investigation

Ground investigations often use trial pits and borehole cores on construction sites to determine the strata likely to be encountered at various depths. The data obtained from trial pits can be coded into a form that can be used as sample observations for input to a grammatical inference machine. A grammatical inference machine is a black box, which when presented with a sample of observations of some unknown source language, produces a grammar which is compatible with the sample. This article presents a heuristic model for a grammatical inference machine, which takes as data sentences and non-sentences identified as such, and is capable of inferring grammars in the class of context-free grammars expressed in Chomsky Normal Form. An algorithm and its corresponding software implementation have been developed based on this model. The software takes, as input, coded representations of ground investigation data, and produces as output a grammar which describes and classifies the geotechnical data observed in the area, and also promises the possibility of being able to predict the likely configuration of strata across the site.

Understanding and exploring formal specifications

Formal methods is seen as a means of applying scientific knowledge to software construction, thereby legitimating the use of mathematics within software engineering. However, the software engineering community faces numerous challenges before an effective transfer of this formal methods technology can take place because of the level of skill, expertise and effort required in their application. It is argued that at present the use of formal notations for system specification is a mature technology offering the greatest leverage. The relative benefits of a declarative approach with a “getting it right the first time” maxim versus an imperative approach coupled with an exploratory trial and error flavour are explored. Detailed characteristics of a teaching and learning environment developed to support the latter approach are provided. Its varied uses in the context of teaching and learning within undergraduate and postgraduate courses in software engineering are discussed. Exemplars from these uses show how users of the environment explore formal specifications to improve their understanding of specification and thereby illustrate the effectiveness of the environment. Implications of our approach on technology transfer and training are briefly explored.

Toolset to support a systematic strategy for AI development

AI developments have been based on an exploratory approach whereas software engineering approaches can be characterised as specification-based. We present an integrated toolset that accommodates and encourages a mixed-mode development, thereby maximising the strengths and minimising the weaknesses of both approaches. Moreover, the interactive nature of the toolset provides an effective means to validate the adequacy of the developing system.