Organising Knowledge of a Federated Database System to Support Multiple View Generation

In this paper a knowledge base structure to support multiple view generation over a federation of loosely-coupled heterogeneous databases available over a computer network is described. In such a federation user information requirements change and evolve as their awareness of the contents of the federation improves. This means that users need diierent integrating views if they are to realise the full potential of the federation. To facilitate the creation of integrating views, users need to know what is available in the federation , how the available information is related semantically and which information has been used together previously. Once integrating views are created, users must be informed when their views become invalid due to changes in the participating databases. The knowledge base is structured primarily to assist users in such tasks. The knowledge stored in the knowledge base is obtained by analysing the meta-data of the databases of the federation and from their respective owners. The knowledge base is built in bottom-up fashion by extracting and merging incrementally, the meta-data of the DBs. The canonical data model used to organise both the meta-data and the knowledge base is also described. Finally a workbench of tools we have developed to assist users to create the knowledge base The copyright of this paper belongs to the paper's authors. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage. and to generate integrating views over the federation is outlined.