Proceedings of the 3rd International Workshop on Interfaces to Databases, Napier University, Edinburgh (IDS-3)
Interfaces to Databases
8-10 July 1996
Data modelling is a crucial and early step in the design of all but the most trivial database systems. Although a fundamental skill for information systems designers, data modelling is not easy to do well and novices are known to have considerable difficulty a) in generating a satisfactory model from a given scenario and b) in appreciating the semantic nuances of a given model from its diagrammatic representation. Given a candidate model, novices typically find it difficult to envisage whether a set of specified query types can be met and what the implications of the model are for storage and access. One of the main differences between novice and expert performance is held to be this capacity to visualise the implications of a model from its diagrammatic representation. These two skills, generation and evaluation, are closely inter-linked: clearly, some competence in the second is necessary for self-monitoring during the model generation process; however, a high degree of facility is required if data modelling is to be truly a design process and not just a mechanistic activity whereby the model is derived from the scenario by simple transformation. The concept of data modelling as design, as a creative process, has been under-emphasised thus far in the pedagogic literature. We aim to broaden the prevalent convergent style of introductory texts (which tend to concentrate students towards the specimen ‘correct’ solution), by promoting a more divergent approach, namely, that there is likely to be a set of feasible solutions, candidate solutions will have advantages and disadvantages and creative solutions may involve a re-conceptualisation of the scenario. To promote these ideas in teaching, supporting tools are needed. While there are a number of software packages existing to help with the graphical aspects of model creation (modelling tools), there is a dearth of software offering modellers an environment in which they can create a model or partial model and then interact with it better to understand its ‘behaviour’. This paper explains the rationale behind and work-in-progress on a concept-demonstrator TOTEM (TOol for TEaching Modelling) which owes much to the new generation of programming environments such as Visual Basic and Delphi. TOTEM is conceived as a Windows-based rapid ‘design and test’ environment for extended Entity-Relationship modelling that supports interaction with multiple candidate solutions, any of which can be explored with test data. We report a video study to assess the usability of design mode in single user, single model conditions and present the main ideas behind the next planned phase of work.