A universal query interface for heterogeneous distributed digital libraries

Various kinds of digital libraries are accessible on the WWW (World Wide Web). The interoperability among those systems is one of the major topics of the digital library community. The paper presents the HyNeSS model and its query interface for that purpose. The HyNeSS model integrates the entity relationship model and predicate logic, and provides a universal and formal expression for network-oriented data. The authors have developed a prototype system of the HyNeSS database system. The query interface is universal in the sense that it does not depend to any particular database schema. It loads the schema information from a remote HyNeSS database system and adapts itself to the given schema. On the submission of a query, the composed expression is converted into a declarative query expression based on predicate logic. It provides a universal expression to retrieve and identify objects in heterogeneous distributed environment