Reusability in software engineering

This paper surveys recent work concerning reusability in software engineering. The current directions in software reusability are discussed, and the two major approaches of reusable building blocks and reusable patterns studied. An extensive bibliography, parts of which are annotated, is included

From spreadsheets to relational databases and back

This paper presents techniques and tools to transform spreadsheets into relational databases and back. A set of data refinement rules is introduced to map a tabular datatype into a relational database schema. Having expressed the transformation of the two data models as data refinements, we obtain for free the functions that migrate the data. We use well-known relational database techniques to optimize and query the data. Because data refinements define bidirectional transformations we can map such database back to an optimized spreadsheet. We have implemented the data refinement rules and we have constructed tools to manipulate, optimize and refactor Excel-like spreadsheets.(undefined

SAGA: A project to automate the management of software production systems

The Software Automation, Generation and Administration (SAGA) project is investigating the design and construction of practical software engineering environments for developing and maintaining aerospace systems and applications software. The research includes the practical organization of the software lifecycle, configuration management, software requirements specifications, executable specifications, design methodologies, programming, verification, validation and testing, version control, maintenance, the reuse of software, software libraries, documentation, and automated management

The effect of multiple knowledge sources on learning and teaching

Current paradigms for machine-based learning and teaching tend to perform their task in isolation from a rich context of existing knowledge. In contrast, the research project presented here takes the view that bringing multiple sources of knowledge to bear is of central importance to learning in complex domains. As a consequence teaching must both take advantage of and beware of interactions between new and existing knowledge. The central process which connects learning to its context is reasoning by analogy, a primary concern of this research. In teaching, the connection is provided by the explicit use of a learning model to reason about the choice of teaching actions. In this learning paradigm, new concepts are incrementally refined and integrated into a body of expertise, rather than being evaluated against a static notion of correctness. The domain chosen for this experimentation is that of learning to solve "algebra story problems." A model of acquiring problem solving skills in this domain is described, including: representational structures for background knowledge, a problem solving architecture, learning mechanisms, and the role of analogies in applying existing problem solving abilities to novel problems. Examples of learning are given for representative instances of algebra story problems. After relating our views to the psychological literature, we outline the design of a teaching system. Finally, we insist on the interdependence of learning and teaching and on the synergistic effects of conducting both research efforts in parallel

A method for maintaining new software

This thesis describes a novel method for perfective maintenance of software which has been developed from specifications using formal transformations. The list of applied transformations provides a suitable derivation history to use when changes are made to the software. The method uses transformations which have been implemented in a tool called the Maintainer's Assistant for the purposes of restructuring code. The method uses these transformations for refinement. Comparisons are made between sequential transformations, refinement calculi and standard proof based refinement techniques for providing a suitable derivation history to use when changes are made in the requirements of a system. Two case studies are presented upon which these comparisons are based and on which the method is tested. Criteria such as saleability, speed, ease, design improvements and software quality is used to argue that transformations are a more favourable basis of refinement. Metrics are used to evaluate the complexity of the code developed using the method. Conclusions of how to develop different types of specifications into code and on how best to apply various changes are presented. An approach which is recommended is to use transformations for splitting the specification so that original refinement paths can still be used. Using transformations for refining a specification and recording this path produces software of a better structure and of higher maintainability. Having such a path improves the speed and ease of future alterations to the system. This is more cost effective than redeveloping the software from a new specification

Proving refinement transformations for deriving high-assurance software

The construction of a high-assurance system requires some evidence, ideally a proof, that the system as implemented will behave as required. Direct proofs of implementations do not scale up well as systems become more complex and therefore are of limited value. In recent years, refinement-based approaches have been investigated as a means to manage the complexity inherent in the verification process. In a refinement-based approach, a high-level specification is converted into an implementation through a number of refinement steps. The hope is that the proofs of the individual refinement steps will be easier than a direct proof of the implementation. However, if stepwise refinement is performed manually, the number of steps is severely limited, implying that the size of each step is large. If refinement steps are large, then proofs of their correctness will not be much easier than a direct proof of the implementation. The authors describe an approach to refinement-based software development that is based on automatic application of refinements, expressed as program transformations. This automation has the desirable effect that the refinement steps can be extremely small and, thus, easy to prove correct. They give an overview of the TAMPR transformation system that the use for automated refinement. They then focus on some aspects of the semantic framework that they have been developing to enable proofs that TAMPR transformations are correctness preserving. With this framework, proofs of correctness for transformations can be obtained with the assistance of an automated reasoning system

The systematic construction of information systems

Process modelling is a vital issue for communicating with experts of the application domain. Depending on the roles and responsibilities of the application domain experts involved, process models are discussed on different levels of abstraction. These may range from detailed regulation for process execution to the interrelation of basic core processes on a strategic level. To ensure consistency and to allow for a flexible integration of process information on different levels of abstraction, we introduce a transformational calculus that allows the incremental addition to and refinement of the information in a process model, while maintaining the validity of more abstract high level processes. A complete formal treatment of model and the calculus is given and is illustrated on a small banking example.Funding received from the UK Engineering and Physical Sciences Research Council (EPSRC) through the Research Grant GR/M/0258