Capturing and matching dynamic behaviour in case-based reasoning

Abstract

In the telecommunications domain, reuse of service specifications is a major issue. However, it has proved difficult to modularise services because of the high degree of interaction between them. Direct application of formal logics to the specification of services has proved impractical because of the size of the services. However, much of this complexity stems from the details of implementation of the services; by contrast, the principal behaviours of a service are often approximated by simple varieties of logic which are easily accessible to users. We address the problem of determining, from a library of services, those which might be appropriate for reuse in constructing a new service. Simple behavioural sequences are used to provide features within a CBR system which matches these to behavioural examples supplied by users. By side-stepping the problem of formally specifying the entire service, we aim to promote greater reuse of services while avoiding a commitment to full logical specification.

Non-mathematicians often have difficulty in expressing requirements formally. By using a CBR approach the user can sketch out simple, familiar behaviours and with these examples the system is able to retrieve relevant cases and interactively produce a formal requirements sketch capturing the new required behaviour. A case in the case library encapsulates a particular formalised behaviour in a simple logic which is sufficient to capture the key dynamic behaviours of the domain. With a simulator the user can evaluate the behaviour without being confronted with the formal representation itself. Our domain is telephone features such as call waiting, redirect call, call back. These telephone services are stored in the case library as cases, each consisting of a set of transition rules. In previous papers we have described the general architecture of the system (see for example [Funk & Robertson 1994]). In this paper we focus on matching dynamic behaviour and the formal representation of the cases.

This research was supported by the Marcus Wallenberg Foundation for Scientific Research and Education and ELLEMTEL Telecommunication Systems Laboratories, Sweden.