Prof Keith van Rijsbergen

Path Dependent Information Retrieval: Answers without Queries

Motivated by the problems arising in image retrieval I will present some ideas about how to model such retrieval in the context of some earlier approaches to text retrieval. In particular I will discuss problems associated with indexing, relevance feedback, browsing when applied to images. The talk will assume little prior knowledge of Information Retrieval. Time permitting I will demonstrate a pathdependent browsing tool implemented to help in the research on image retrieval.

Ivan Damgaard

Unconditional Security Cryptography: Was Shannon too pessimistic?

Unconditionally secure communication means that even an infinitely powerful adversary cannot break the confidentiality nor the authenticity of the system. Classical results by Shannon dating back some 50 years seem to imply that unconditionally secure solutions are doomed to being impractical, if not impossible. However, in recent years, new research has shown that these results were based on rather pessimistic assumptions on the amount of information available to an adversary. It turns out that in many practical scenarios, these assumptions are not satisfied, e.g., when communciation is noisy, in large networks where not all nodes can be hacked into, or when quantum communication is used. In all these settings, unconditional security is indeed possible. We will survey some results in this area, with particular emphasis on quantum communcation.

Professor Les Hatton

"A long hard look at the influence of software defects on scientific and other software"

Scientific software and the science of simulation has grown very quickly to fill the needs placed upon it by society, which in turn now completely depends on those simulations. Every area of human activity is affected to some degree. Unfortunately, whereas the science involved in specifying a simulation is the subject of a generally careful and effective peer review system, the resulting software is not. As a result, latent faults in the software can easily survive simulation testing and cause failure of the resulting system. As scientists, we should not forget that doing the science is usually the easy bit. Producing a defect-free implementation of anything but the most trivial of simulation algorithms seems entirely beyond the capabilities of computer science at the present stage of development and is likely to remain so for the foreseeable future. Society and indeed scientists will therefore have to learn how to assess and live with this risk. This seminar is a personal view of this problem and summarises 15 years of experiments by the author and collaborators in trying to understand the underlying patterns behind software failure. These will be illustrated using the results of very large experiments on software failure carried out at various stages over this period in many different industries. Is it getting any better ? No. Could we do better ? Yes, much.

Peter Amey

Logic versus Magic in Critical Systems

A prevailing trend in software engineering is the use of tools which apparently simplify the problem to be solved. Often, however, this results in complexity being concealed or "magicked away". For the most critical of systems, where a credible case for safety and integrity must be made prior to there being any service experience, we cannot tolerate concealed complexity and must be able to reason logically about the behaviour of the system. The presentation draws to on real life project experience to identify some historical and current magics and their effect on high integrity software development; this is contrasted with the cost and quality benefits that can be made from taking a more logical and disciplined approach.