Building DD to Support Query Processing in Federated Systems

In this paper, a method for building data dictionaries (DDs) is discussed, which can be used to support query processing in federated systems. In this method, the meda data stored in a DD are organized into three classes: structure mappings, concept mappings and data mappings. Based on them, a query submitted to a federated system can be decomposed and translated, and the local results can be synthesised automatically. 1 Introduction Due to the rapid advance in networking technologies and the requirement of data sharing among different organizations, federated systems have become the trend of future database developments [BOT86, LA86, Jo93, SK92, CW93, HLM94, RPRG94, KFMRN96]. The research on this issue can be roughly divided into two main categories: the tightly-integrated approach that integrates databases by building an integrated schema and the loosely-integrated approach that achieves interoperability by using a multidatabase language. The method proposed here belongs to the sec..