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Manual software design methods suffer from many handicaps. As a result, the design documentation of software systems usually either does not exist, or is full of errors and out of date. Many software development, reliability, and maintainability problems reported in the literature can be traced to this state of affairs. The solution of these problems does not appear to lie in improved manual software design methods, but in the potentially much more "effective" computer-aided software design tools. This project set out to investigate how to aid the manual software design methods with a computer. A novel entity-relationship model for the software design specification was formulated and built into an interactive pilot software design tool. In spite of its simplicity, the model is capable of representing software structures from high-level architectural design to low-level detailed design. The tool stores the model entered by the user in a database. The model can then be inspected either on-line, or from printed documentation. The evaluation of the pilot tool, based on the feedback from the users, was favourable to the underlying model. However, many human-computer interface problems were identified. The effectiveness of software design tools was defined in terms of the designer productivity and the quality of the design documentation. An approach which consisted of repeated propositioning, implementation, and evaluation of modifications was then used to improve the effectiveness of the tool. A questionnaire was used to assess the opinion of the tool users more objectively, and an experiment was carried out to compare the effectiveness of the tool with a manual method. The results of this research have shown that the latest version of the tool is significantly more effective than the manual method.

Evidence from literature indicates prevailing issues in relation to the documentation of software systems. Documentation requires significant effort to create and maintain and this can often reduce the inclination to produce it in a timely manner and to ensure that it remains up to date with the program which code it corresponds to. As a result, documentation is not entirely trusted as a source of consultation during software maintenance tasks. Existing tool support neglects important aspects of detailed design documentation for software systems. This work proposes a design for a novel research tool which provides improved support for the detailed design and documentation of software systems and which addresses the prevailing issues identified. At the core of this tool is a ‘dynamic synchronization’ feature which automates the process of detecting and synchronizing changes between program code and documentation at the level of detailed algorithms in code; preventing them from getting out of date. An evaluation experiment was designed and conducted wherein the research tool was used to complete a series of programming and documentation tasks representing typical software development and code maintenance scenarios. The results show that software developers using the dynamic synchronization feature had a significant 66 percent reduction in the time required to keep their documentation up to date during a code maintenance task (p < 0.01), and a significant 31 percent reduction in the time to complete the maintenance task (p < 0.01). In a questionnaire, they expressed a significant 20 percent higher confidence level that their documentation was an accurate reflection of their code than software developers using non-synchronized forms of documentation (subjective measure, p = 0.03). Further areas of research and development are proposed.

Current fashion in "user-friendly'' software design tends to place an overreliance on direct manipulation interfaces. To be truly expressive (and thus truly user-friendly), applications need both learnable interfaces and domain-enriched languages that are accessible to the user. This paper discusses some of the design issues that arise in the creation of such programmable applications. As an example, we present "SchemePaint", a graphics application that combines a MacPaint-like interface with an interpreter for (a "graphics-enriched'') Scheme.

The commercial need to capture, process and represent the shape and form of an outline has lead to the development of a number of spline routines. These use a mathematical curve format that approximates the contours of a given shape. The modelled outline lends itself to be used on, and for, a variety of purposes. These include graphic screens, laser printers and numerically controlled machines. The latter can be employed for cutting foil, metal. plastic and stone. One of the most widely used software design packages has been the lKARUS system. This, developed by URW of Hamburg (Gennany), employs a number of mathematical descriptions that facilitate the process of both modelling and representation of font characters. It uses a variety of curve formats, including Bezier cubics, general conics and parabolics. The work reported in this dissertation focuses on developing improved techniques, primarily. for the lKARUS system. This includes two algorithms which allow a Bezier cubic description, two for a general conic representation and, yet another, two for the parabolic case. In addition, a number of algorithms are presented which promote conversions between these mathematical forms; for example, Bezier cubics to a general conic form. Furthennore, algorithms are developed to assist the process of rasterising both cubic and quadratic arcs.