One testbed for examining formal methods is a software project course. The author describes how the software process model used for such a course is now at the point where students are required to adopt an entirely formal approach to the development of their software projects. This software process model also strictly separates the responsibility for building a software system from the responsibility for specifying it; a separation that is facilitated by the use of formal notation to achieve precise communication. The author describes this software development process and assesses it both from an engineering and from an educational perspective. He also identifies areas where the effectiveness of formal methods must be further increased.>

Problems in geometry often possess symmetry properties that may be exploited in order to develop solutions. Algorithms based on these symmetry properties will frequently use geometric transformations to transform one case into another (symmetric) case. One advantage of this approach is that the algorithm avoids enumeration of cases and thus is shorter and generally easier to read. One disadvantage is that some additional execution time is required to perform these transformations. We describe how simple program equivalences may be used as program transformations to eliminate this additional execution time from programs that use geometric transformations. This approach has been used to develop an efficient implementation of a new algorithm for the two-dimensional line-clipping problem.

Formal specification methods are being used to improve the quality of written specifications and to eliminate errors at an early stage of software development. The detection of errors in a specification generally requires that the specification be compared against some loosely defined real-world concepts. A criterion for evaluating the quality of a model-oriented specifications is introduced and the problems associated with specifications which do not meet this criterion are explained. These problems are particularly troublesome when reusable software components are being specified or when a bottom-up implementation strategy is being used.>

The author describes a software tool that supports transformation and verification activities, as well as some more widely used dynamic analysis activities. How the design of this tool supports not only the different activities but also their interaction is explained and the advantages of integrating these activities are briefly discussed. The author reports on the current status of the implementation and on enhancements that are being implemented.>

An integrated life-cycle model is presented for use in a software maintenance environment. The model represents information about the development and maintenance of software systems, emphasizing relationships between different phases of the software life cycle. It provides the basis for automated tools to assist maintenance personnel in making changes to existing software systems. The model is independent of particular specification, design, and programming languages because it represents only certain 'basic' semantic properties of software systems: control flow, data flow, and data structure. The software development processes by which one phase of the software life cycle is derived from another are represented by graph rewriting rules, which indicate how various components of a software system have been implemented. This approach permits analysis of the basic properties of a software system throughout the software life cycle. Examples are given to illustrate the integrated software life-cycle model during evolution.>

This paper describes a new alorithm for clipping a line in two dimensions against a rectangular window. This algorithm avoids computation of intersection points which are not endpoints of the output line segment. The performance of this algorithm is shown to be consistently better than existing algorithms, including the Cohen-Sutherland and Liang-Barsky algorithms. This performance comparison is machine-independent, based on an analysis of the number of arithmetic operations and comparisons required by the different algorithms. We first present the algorithm using procedures which perform geometric transformations to exploit symmetry properties and then show how program transformation techniques may be used to eliminate the extra statements involved in performing geometric transformations.