Formalizing graphical notations

The thesis describes research into graphical notations for software engineering, with a principal interest in ways of formalizing them. The research seeks to provide a theoretical basis that will help in designing both notations and the software tools that process them. The work starts from a survey of literature on notation, followed by a review of techniques for formal description and for computational handling of notations. The survey concentrates on collecting views of the benefits and the problems attending notation use in software development; the review covers picture description languages, grammars and tools such as generic editors and visual programming environments. The main problem of notation is found to be a lack of any coherent, rigorous description methods. The current approaches to this problem are analysed as lacking in consensus on syntax specification and also lacking a clear focus on a defined concept of notated expression. To address these deficiencies, the thesis embarks upon an exploration of serniotic, linguistic and logical theory; this culminates in a proposed formalization of serniosis in notations, using categorial model theory as a mathematical foundation. An argument about the structure of sign systems leads to an analysis of notation into a layered system of tractable theories, spanning the gap between expressive pictorial medium and subject domain. This notion of 'tectonic' theory aims to treat both diagrams and formulae together. The research gives details of how syntactic structure can be sketched in a mathematical sense, with examples applying to software development diagrams, offering a new solution to the problem of notation specification. Based on these methods, the thesis discusses directions for resolving the harder problems of supporting notation design, processing and computer-aided generic editing. A number of future research areas are thereby opened up. For practical trial of the ideas, the work proceeds to the development and partial implementation of a system to aid the design of notations and editors. Finally the thesis is evaluated as a contribution to theory in an area which has not attracted a standard approach

Modelling and analysis of parallel information systems.

This thesis presents an investigation of modelling and analysis of parallel information systems. The research was motivated by the recent developments in networks and powerful, low-cost, desk top multiprocessors. An integrated approach for the construction of parallel information systems was developed which focussed on modelling, verification and simulation of such systems. The thesis demonstrates how Petri nets can be used for the modelling and analysis of entity life histories and parallel information systems, place transition nets for the modelling and analysis of entity life histories and coloured Petri nets for the modelling and analysis of complex parallel information systems. These tools were integrated into a comprehensive framework which allowed for the modelling and analysis of complex parallel information systems and the framework was tested using a comprehensive case study. The thesis concludes that Petri nets are an ideal tool for the modelling and analysis of complex parallel systems. Verification is possible with deadlocks and similar properties being easily identified. Further the transformation rules proved to be beneficial to the process of moving from one model to another. Finally simulation of parallel behaviour was possible because the underlying models captured the notion of parallelism