Sam Waugh

An empirical investigation of multiple viewpoint reasoning in requirements engineering

Multiple viewpoints are often used in requirements engineering to facilitate traceability to stakeholders, to structure the requirements process, and to provide richer modelling by incorporating multiple conflicting descriptions. In the latter case, the need to reason with inconsistent models introduces considerable extra complexity. We describe an empirical study of the utility of multiple world reasoning (using abduction) for domain modelling. In the study we used a range of different models (ranging from correct to very incorrect), different fanouts, different amounts of data available from the domain, and different modelling primitives for representing time. In the experiments there was no significant change in the expressive power of models that incorporate multiple conflicting viewpoints. Whilst this does not negate the advantages of viewpoints during requirements elicitation it does suggest some limits to the utility of viewpoints during requirements modelling.

Evaluating a Qualitative Reasoner

In order to support verification, validation and analysis of dynamic Operations Research (OR) models a method of testing models against data is required. In the case of the QCM qualitative reasoning system (QRS) this requires an extension to accommodate temporal data streams. This paper examines a number of temporal reasoning methods for QCM. On the basis of this a general methodology for evaluating QRSs and a statement of success criteria have been developed, and will be used in future work.

On the Practicality of Viewpoint-Based Requirements Engineering

Requirements engineering is often characterised as the management of conflicts between the viewpoints of different stakeholders. This approach is only useful if there is some benefit in moving a specification from one viewpoint to another. In this study, the value of different viewpoints was assessed using a range of different models (ranging from correct to very incorrect), different fanouts, different amounts of data available from the domain, and different temporal linking policies. In all those models, no significant difference was observed between viewpoints.

Lower Bounds on the Size of Test Data Sets

Practically speaking, how small can a test suite be and still be of value? In the context of temporal graph-theoretic abductive validation, the answer to this question is very language-dependent. Seemingly trivial variations in a language can have a significant impact on how large a test suite must be. This paper is hence a cautionary note to those who invent languages and ontologies without experimentally testing the practicality of those languages.

The Temporal QCM Modelling Language

We examine the QCM language for qualitative compartmental modelling, along with temporal extensions to that framework (TQCM). We identify translations of QCM and TQCM which are explanatory as well as descriptive, adding to our ability to correctly verify qualitative models. The reasoning about such explanatory translations is supported by the reported experimental results.