Colin C. Charlton

Interactivity and collaboration on the WWW — is the ‘WWW shell’ sufficient?

Abstract The web and its associated technologies — Cgi-scripts, JavaScript and Java — have become a platform for the development and deployment of applications. Such has been the impact of these technologies that their combination has been likened to an Expert System Shell, and referred to by the term ‘WWW shell’. This WWW shell it is claimed is particularly adapted to the development of collaborative applications. This paper challenges this claim on three grounds: browser incompatibilities limit the potential benefits from client-side processing technologies; the generic Common Gateway Interface as an application delivery mechanism is inadequate and the networking restrictions on Java applets constrain effective use of the latter as dedicated interfaces to remote applications. This argument is illustrated with respect to three case studies of practical collaborative applications of WWW shell technology. The paper concludes by exploring the implications of new server side technologies, in particular Java servlets for the future development of the WWW shell and the evolution of an ‘Active Web’.

Diffusion of the Internet: a local perspective on an international issue

The rapid growth of the Internet in recent years has received considerable attention. Closer examination of the growth of the Internet however reveals some interesting limitations to the diffusion pattern that has been demonstrated to date. More widespread use of the Internet as a communications technology depends on new partnerships being formed which cross the traditional divides between the world cf business, the world of academia and that of grass roots community life. An example of such a partnership in the Merseyside area is presented.

Bringing the internet to the community

Abstract Current developments in browser technology have largely ignored academic research on interface design in hypermedia systems. This is unlikely to change in the future. Thus, the needs of an information society must be met by providing appropriate training in the use of the technology in the community. To be effective, such training has to identify the difficulties computer-naive members of the public experience with existing systems and to consider both software and training based solutions to these problems. This paper seeks to encourage debate about strategies for facilitating access to Internet technology in the community by reviewing both the success and the difficulties encountered in a public access to the Internet outreach programme, the Internet Express, currently operating at libraries in Merseyside, UK.

Lazy simulation of digital logic

The use of software simulators as a means for developing and validating digital-logic systems has become well established, and the complexity of todays circuits makes the accuracy and efficiency of simulation of prime importance. It is suggested in the paper, however, that conventional simulation techniques are inadequate for this purpose: to represent the inherently parallel activity of a digital circuit in a sequential simulation program, an unnecessary, and often arbitrary, sequence of events is imposed. This is a process that is error-prone and inefficient. In an attempt to reason about the nature of the simulation problem, a model of hardware has been derived that makes use of the principles involved in functional programming; in particular, the concept of lazy evaluation has been adopted as a way of minimizing the amount of simulation activity required. This model has been used as the basis for the generation of several simulators, and the paper presents an analysis of the performance of such a lazy simulator in comparison with those of the more usual simulation mechanisms. The results of this are extremely encouraging.

A note on recreating source code from the reverse polish form

Algorithms are presented which recreate infix form from reverse Polish form of algebraic expressions. The use of these algorithms in incremental compilers is discussed.

Good business practice needs good communications-new generation chat software for real-time discussion

Whilst the email and newsgroups have long been recognised as commercially useful tools, chatroom technology has generally been regarded as a somewhat frivolous application. Chatrooms however may serve a variety of useful commercial and educational as well as recreational purposes. Each context of use, however, has its own requirements. Consequently, there is a need for the design of generic software for chatroom generation which is readily configurable to the requirements of a context and which is also extensible. The design requirements of such a system are discussed and a novel generic system, ChatterBox, implemented in Java, is presented.

An object-oriented model of design evolution

Abstract The paper presents a general model of design evolution, intended to be shared by all forms of digital circuit CAD data subject to change. This provides a common view of design evolution, based on immutable design states. This view simplifies concurrent access control and consistency maintenance. Object-oriented inheritance is used to specialise the general model for particular forms of information, which may need their histories managed in different ways. Two examples are described; one is based on differential representations of successive states and is suited tomanaging evolution in an editor environment, and the other is appropriate for managing untracked changes in an automatically generated design.

The impact of the new connectivity: transferring technological skills to the small business community

This paper describes a set of strategies developed by the Department ofcomputer Science, Liverpool University to promote the necessary conditions for electronic commerce within the Mcrscyside Region of the UK. The implications of these strategies for the IT professionals involved in the project, for the utilisntion of skills among unemployed computing professionals and for the relationship of the business to the University community are discussed.

Program monitoring and analysis: software structures and architectural support

The ability to monitor the progress of a program in execution is useful in program testing and debugging, and for performance analysis and profiling. Systems to support this activity should ideally be high‐level‐language based, but progress in implementing them has been limited by the lack of suitable hardware support. In this paper we derive software structures to support a generalized system of execution monitoring, and define a set of architectural primitives sufficient to support these structures. Simple and efficient means of implementing these primitives within the machine architecture are described.

A microprogram meta-disassembler

Abstract A meta-assembler is a program which can be configured to perform translation from any defined assembly-language form into machine code. This paper describes a meta-disassembler which will perform the reverse translation for a class of instruction and language forms. It has been designed particularly to deal with the problems of disassembling horizontal microcode to produce a microinstruction execution history. The meta-disassembler is used as part of a set of retargetable software tools to assist to microprogram development and analysis.