Specification and design of an information system conventionally starts from consideration of the system function. This paper argues that consideration may more properly be given first to the system as a model of the reality with which it is concerned, the function being subsequently superimposed on the model.The form of model proposed is a network of sequential processes communicating by serial data streams. Such a model permits a clear representation of change or activity over time, and it also prevents over-specification of sequencing by separating problem-oriented from solution-oriented sequencing constraints. The model, however, cannot be efficiently executed on uniprocessor hardware without transformation. Some relevant kinds of transformation are mentioned, and the derivation, by means of them, of conventional information system configurations from the proposed model.

Information Systems: Modelling, Sequencing and Transformations.

Using Category Theory to Verify Implementation Against Design in Concurrent Systems

: The service life of military assets significantly exceeds design life of commercial electronic systems used within them. Electronic obsolescence is increasingly associated with physical characteristics that reduce component and system reliability, both in usage and storage, with few design margins outside commercial warranty periods. Software content, however, remains a dominant limiting factor for reliability of electronic systems, and emerging commercial trends compound this. Traditional approaches to manage and sustain electronic systems are therefore increasingly ineffective and costly. This report surveys the interrelated concerns of obsolescence and reliability of electronic systems, and describes emerging responses to these concerns.

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A Survey of Electronics Obsolescence and Reliability

Since Hoare introduced Communicating Sequential Processes as a model of distributed computation, there has been much discussion about efficient and flexible implementations Previous research has led to communication protocols with restrictions: a process may only choose amongst receive operations; only a single pair of processes can be connected to a channel; or the protocol may be subject to deadlock or lack of fairness We describe a fair protocol that allows arbitrary, non-deterministic communication amongst a set of processes connected by channels

A fair protocol for non-deterministic message passing

The increasing significance of concurrency and the need to address the challenges presented by concurrency motivate its formalization. In this paper, a methodology for modeling and verifying communications in a concurrent system developed in Erasmus, a process-oriented programming language, is proposed. The innovative aspects of this methodology include the use of category theory to model and verify properties of communications in Erasmus, and the use of data flow to analyze and abstract an implementation of Erasmus. The methodology is illustrated by a simple example.

Using Category Theory and Data Flow Analysis for Modeling and Verifying Properties of Communications in the Process-Oriented Language Erasmus

Software systems bridge the gap between information processing needs and available computer hardware. As system requirements grow in complexity and hardware evolves, the gap does not necessarily widen, but it certainly changes. Although today's applications require concurrency and today's hardware provides concurrency, programming languages remain predominantly sequential. Concurrent programming is considered too difficult and too risky to be practiced by "ordinary programmers". However, software engineering is moving towards a paradigm shift, following which concurrency will play a more fundamental role in programming languages. We discuss some of the implications of the shift towards process-oriented programming. We outline some of the features of our own process-oriented language. Finally, we review the potential impact on software engineering and on software development processes.

Concurrent software engineering: preparing for paradigm shift

Software systems bridge the gap between the information processing needs of the world and computer hardware As system requirements grow in complexity and hardware evolves, the gap does not necessarily widen, but it undoubtedly changes Although today’s applications require concurrency and today’s hardware provides concurrency, programming languages remain predominantly sequential Concurrent programming is considered too difficult and too risky to be practiced by “ordinary programmers” Software development is moving towards a paradigm shift, following which concurrency will play a fundamental role in programming In this paper, we introduce an approach that we believe will reduce the difficulties of developing and maintaining certain kinds of concurrent software Building on earlier work but applying modern insights, we propose a programming paradigm based on processes that exchange messages Innovative features include scale-free program structure, extensible modular components with multiple interfaces, protocols that specify the form of messages, and separation of semantics and deployment We suggest that it may be possible to provide the flexibility and expressiveness of programming with processes while bounding the complexity caused by

MODULAR CONCURRENCY - A New Approach to Manageable Software

4. Scope Rules 3 4.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.2. Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4.3. Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.3.1. Module Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.3.2. Local Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Brian Shearing

Papers

Concurrent software engineering: preparing for paradigm shift

MODULAR CONCURRENCY - A New Approach to Manageable Software

Desi: Erasmus for 2010