Technical Reports at the Centre for Research in Computing

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[1] Lynne Dunckley, Lucia Rapanotti, and Jon G. Hall. Extending low-cost remote evaluation with synchronous communication. Technical Report 2002/02, 2002. [ bib | .pdf ]
Write-along Low Cost Remote (LCR) evaluation has been proposed as a highly efficient method for remotely evaluating usability problems with prototype interfaces. In a previous study, it was noted that this efficiency was at the cost of a loss of the conversational nature of the evaluation present in think-aloud methods. In this paper, we assess this loss through a comparison with an extended LCR, which uses real-time conferencing tools to introduce synchronous communication. An experimental investigation was carried out on an interactive prototype interface with known usability problems. In this way the effectiveness of the new method using real-time conferencing tools could be assessed and recommendations for best practice set out.

[2] Lucia Rapanotti, Canan Tosunoglu Blake, and Robert Griffiths. etutorials with voice groupware: an investigation into real-time conferencing to support m206 students at a distance. Technical Report 2002/03, 2002. [ bib | .pdf ]
This paper reports on an investigation into the use of real-time voice groupware to support students on a computing course offered by the Open University, UK. The main objective of the investigation was to assess the feasibility and pedagogical advantage of deploying synchronous conferencing technology on a large population computing course to complement existing face-to-face and asynchronous online support for its students. In this paper we report on the findings from such an investigation, and draw a number of conclusions and recommendations covering feasibility, scalability and best practice in the use of voice groupware for eLearning.

[3] Jon G. Hall, Michael Jackson, Robin C. Laney, Bashar Nuseibeh, and Lucia Rapanotti. Relating software requirements & architectures using problem frames. Technical Report 2002/04, 2002. [ bib | .pdf ]
Problem frames provide a means of analyzing and decomposing problems. They emphasise the world outside of the computer, helping the developer to focus on the problem domain, instead of drifting into inventing solutions. However, even modestly complex problems can force us into detailed consideration of the architecture of the solution. This is counter to the intention of the problem frames approach, which is to delay consideration of the solution space until a good understanding of the problem is gained. We therefore extend problem frames, allowing architectural structures, services and artifacts to be considered as part of the problem domain; in essence, the machine domain of a problem frame is lifted from being a 'general purpose machine' to be a specialised ‘architecture engine' (having architectural structures, services and artifacts ‘built in'). The task of designing the machine domain is thus lifted to above the level that those architectural artifacts provide. Through a case study, we show how this extension enhances the applicability of problem frames in permitting an architecture-based approach to software development therein. We conclude that, through our extension, the applicability of problem frames is extended to include domains with existing architectural support.

[4] Lynne Duckley, Lucia Rapanotti, and Jon G. Hall. Low cost remote evaluation with synchronous groupware. Technical Report 2002/05, 2002. [ bib | .pdf ]
The paper reports a refinement of the remote evaluation method of [2], that includes synchronous groupware with audio over the Internet. The method applies ideas from contextual inquiry and participatory design for the formative evaluation of a prototype linked to a subsequent redesign process. The investigation involves the Open University - the major provider of distance education in the UK and Europe. The paper describes the refined method, and discusses the findings of an investigation into its characteristics.

[5] Adrian Hilton and Jon G. Hall. Refining specifications to programmable logic. Tutorial 2002/06, 2002. [ bib | .pdf ]
Combined hardware/software systems are increasingly being used for safety-critical systems, with hardware taking processing load off the software. To attain the necessary safety integrity levels, new safety standards require that the correctness arguments for safety-critical hardware and software are developed together with the same rigour as for software alone.In this paper we describe work in progress on the continuing development of such a notation and proof system. Based on process description using Synchronous Receptive Proof Theory, we propose refinement rules for developing a specification into an SRPT implementation. As illustration, we demonstrate the full formal refinement of a 2<sup>k</sup> bit carry look-ahead adder into a Pebble implementation, and test the implementation.

[6] Adrian Hilton and Jon G. Hall. Targeting plds for high-level high integrity systems development. Technical Report 2002/07, 2002. [ bib | .pdf ]
Combined hardware/software systems are increasingly being used for safety-critical systems, with hardware taking processing load off the software. We have produced a design template that allows SPARK Ada, a programming language used for safety-critical systems development, to be compiled and interpreted on programmable logic devices. In this paper we describe a high-integrity PLD-based interpreter for compiled Ada code. The intention is to allow developers to select sections of a SPARK Ada program to be interpreted on hardware, rather than run in software, in parallel with the rest of the program running on a conventional CPU. This extends the reach of high integrity systems development to encompass PLDs.

[7] Henrik S. Gedenryd, Simon Holland, and David R. Morse. Meeting the software engineering challenges of interacting with dynamic and ad-hoc computing environments. Technical Report 2002/08, 2002. [ bib | .pdf ]
We argue that the normal circumstances for pervasive computing technologies will be dynamic and ad-hoc settings, in that the available technical resources will evolve and/or change frequently, rather than having been installed by design. We describe a second-generation software architecture for Ambient Combination [14], engineered to meet the software engineering challenges of achieving transparency of use under such conditions. The architecture uses advanced software composition techniques closely related to aspect-oriented programming, along with computational reflection, to represent domain objects and their properties at a problem-oriented, high conceptual level. This architecture achieves a very good separation of concerns, while also providing the flexibility and extensibility needed to address the open-ended nature of these situations. This also enables the architectural building blocks to be flexible distributed across different machine configurations in an uncomplicated and robust manner.

[8] Henrik S. Gedenryd. Beyond inheritance, aspects & roles: A unified scheme for object and program composition. Technical Report 2002/09, 2002. [ bib | .pdf ]
The areas of inheritance, aspect-oriented programming and rolebased decomposition share the same problem: For all three, the number of candidate schemes is large, all of them different and none of them clearly superior to the rest. Instead of proposing another variation on any of them, this paper presents a simple, unified approach to program composition. The scheme is shown to be compositionally complete, that is, to be sufficient for defining any program composition that is theoretically possible, and therefore forms a superset of all other approaches to program composition. The paper shows how this scheme specifically may supersede inheritance, aspects, and roles. It goes on to show via examples how the scheme can be used as a practical objectoriented language construct. Lastly, it demonstrates how the scheme can be combined with program specialization to yield very good runtime performance. This scheme can make objectoriented languages smaller, yet substantially more powerful and expressive than they currently are.

[9] David R. Morse, Henrik S. Gedenryd, and Simon Holland. A simple, technology-neutral lingua franca for location systems, applied to combined indoor-outdoor navigation. Technical Report 2002/10, 2002. [ bib | .pdf ]
One of the challenges in ubiquitous computing research has been that no single location sensing technology is likely ever to meet all requirements. This has led to the development of a number of technical solutions and infrastructures that attempt to hide the complexities of dealing with more than one location sensing technology behind a consistent Applications Programmers Interface. In this paper we propose a lingua franca for location sensing technologies that emphasises simplicity and universality. Our proposal is not tied to any particular location sensing technology and it can be applied to all locations, both outdoors and indoors. In addition, the paper describes a prototype navigation application that has been applied to a retail shopping scenario, in situations where more than one location sensing technology is required.

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