The success of large software engineering projects depends critically on the specification, which must represent the requirements of a large number of people with widely differing perspectives. Conventional approaches to software engineering do not address the process of identifying and integrating these perspectives, but instead concentrate on the maintenance of a single consistent description. This results in a specification which represents only one point of view, often the analyst's, excluding suggestions which do not fit with this view. The processes which led to the adoption of this point of view will go unrecorded, making any rationale attached to such a specification incomplete. Other participants will not be able to validate it properly, as it does not relate to their requirements. This thesis integrates ideas drawn from the study of knowledge acquisition, computer-supported co-operative work and negotiation into a model of the specification activity which allows the capture ...

Distributed systems may be specified in Structured Modal Action Logic by decomposing them into agents which interact by sharing attributes (memory) as well as actions. In the formalism we describe, specification texts denote theories, and theories denote the set of semantic structures which satisfy them. The semantic structures are Kripke models, as is usual for modal logic. The "possible worlds" in a Kripke model are the states of the agent, and there is a separate relation on the set of states for each action term. Agents potentially share actions as well as attributes in a way controlled by locality annotations in the specification texts. These become locality axioms in the logical theories the texts denote. These locality axioms provide a refined way of circumscribing the effects of actions. Safety and liveness conditions are expressed (implicitly) by deontic axioms, which impose obligations and deny permissions on actions. We show that "deontic defaults" exist so that the specifi...

. The problem of analysing the effects of changing requirements imposes strict demands on system representations, particularly in safetycritical domains. We argue that solving this problem will require structured representations that highlight the interaction between requirements, and record the rationale for decisions made during the development process. As a means of providing and analysing this information, we propose the use of a goal-oriented model for structuring requirements and the use of formal reasoning techniques to aid in the analysis of changes and their consequences. 1 Introduction The need to analyse the effects of changing requirements adds to the demands on system representations. In addition to verifying the integrity of the initial system, we would like to have the capability to trace the implications of changes through the system, and also to reason back from desired outcomes to determine what changes could bring them about. These capabilities rely upon a represen...

A Prolog implementation of a new theorem-prover for first-order classical logic is described. The prover is based on the calculus KE and the rules used for analysing quantifiers in free variable semantic tableaux. A formal specification of the rules used in the implementation is described, for which soundness and completeness is straightforwardly verified. The prover has been tested on the first 47 problems of the Pelletier set, and its performance compared with a state of the art semantic tableaux theorem-prover. It has also been applied to model building in a prototype system for logical animation, a technique for symbolic execution which can be used for validation. The interest of these experiments is that they demonstrate the value of certain `characteristics' of the KE calculus, such as the significant space-saving in theorem-proving, the mutual inconsistency of open branches in KE trees, and the relation of the KE rules to `traditional' forms of reasoning. 1 Introduction 1.1 Ov...

We extend the traditional notion of specification based on theories and interpretations between theories to model situations, typical of open, reactive systems, in which properties exhibited locally by an object no longer hold when that object is interconnected as a component of a larger system. The proposed notion of specification is based on the observation, due to Winskel, that while some assertions are preserved across morphisms of labelled transition systems, other are reflected. The distinction between these two classes of assertions leads us to the definition of two categories of specifications, one that supports horizontal structuring and another that supports vertical structuring, for which compositionality is proved. 1 Introduction The notion of a specification as a collection of sentences in some logic (theory presentation) expressing the properties that the program is required to satisfy, and of specification morphism as a property preserving mapping (interpretat...

The CEC Project GOAL (Esprit 6283) aims to develop generic software tools to support a new project management paradigm, in which projects are collaborative, decentralised and inter-organizational. Each partner in such a project will operate a GOAL tool, which includes a knowledge base describing that partner's role in the project. Overall project information is therefore distributed amongst the partners: to provide convenient access to this information we have implemented a system which provides `added value' message reception services to a GOAL tool. This system uses a `local' knowledge base to respond with co-operative answers to natural language queries which are submitted by electronic mail. At this stage of development the system is a prototype, but it is also, we believe, a successful proof of concept and a demonstration of how Artificial Intelligence technologies -- like natural language processing, automated reasoning and deductive databases -- can support the management of int...

Natural language software tools may have an important role in making requirements specifications more accessible. Possible tools include text processors to support requirements elicitation, and text generators to support requirements validation. The current paper reports on our progress in developing a natural language generation system, integrating this tool with a graphical interface and an automated reasoning system, and applying it in the domain of requirements validation. The resulting synthesis of logic, language and graphics is an important first step in developing an intelligent assistant to support a designer in both requirements elicitation and validation. 1 Introduction The requirements specification for any system, written in some combination of diagrams and natural language, may be difficult for a designer or manager to reason about, just because of its complexity. An equivalent specification, written in a formal language, can also cause problems. It may be difficult to c...

This report gives an overview of work done in the `Investigate KBS Support' area of the GMARC project. Major achievements in this area are described, a number of important issues are identified and the relevance of these issues to the development of a knowledge-based tool to support use of the GMARC are discussed. 2 1 Introduction 1.1 Objectives This report is the final deliverable of the GMARC project work package WP44. It is the last in a series of four documents intended to result from the `Investigate KBS support' work area. The first of these documents, R41 [BJT + 91], presented a review of a number of approaches to providing knowledge-based support for requirements elicitation. The second, R42 [BJT + 92a], proposed an approach to the provision of knowledge-based support for requirements elicitation and specification. In this approach, networks of domain knowledge may be used and reused to create formal requirements models for a variety of systems in the domain of inte...

This report presents a brief review of work on the development of knowledge based tools for requirements capture. A number of different approaches are considered, and an attempt is made to draw these together into a common framework. On the basis of this review, a number of suggestions are made regarding the possibility of providing knowledge based support for a generic approach to requirements capture such as GMARC. 4 1 Introduction Requirements engineering is a knowledge intensive activity: according to Curtis [Cur87], `knowledge application is the key to effective software development'. The incorporation of facilities to provide intelligent or knowledge-based support into the current generation of computer-based tools for requirements capture is therefore likely to lead to enormous benefits in terms of productivity gains. A number of different kinds of knowledge and a number of different AI techniques are likely to be of use. This report presents a brief review of techniques ...

ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.2.4 Structuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.2.5 Comprehensibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.3 Choice of a formal notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 5 Requirements of the approach 24 5.1 Domain models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.1.1 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.1.2 User interface for creating and maintaining domain models . . . . . . 24 5.1.3 Domain model creation and maintenance operations . . . . . . . . . . 25 5.2 Requirements models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.2.1 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 5.2.2 User interface for creating and maintaining requirements models . . . 25 5.2.3 Requirements model creation and ...