A visual query interface for a customisable schema visualisation system

Resolving different levels of heterogeneity present in heterogeneous database environments is a subject that has been addressed in a number of research projects. Graphical user interfaces are becoming the de-facto form of user interface in many application areas, including database management systems. The use of a popular visualisation notation to present schemas at an abstract level and to permit direct user manipulation of this visualisation in formulating queries is one of the most widespread approaches to providing database graphical user interfaces. The existence of a variety of visualisation notations (which are in common use to visualise schemas) introduces additional heterogeneity to a distributed system, in visual representation at the end-user interface level. This paper describes the use of meta-programming techniques which are applied to resolve this visual model heterogeneity on existing databases, by allowing a user to select a preferred visualisation notation, both to view the schema and to query the database