Integrating Bibliographical Data from Heterogeneous Digital Libraries Eike Schallehn, Martin Endig, Kai-Uwe Sattler Otto-von-Guericke-University Magdeburg Institute for Technical and Business Information Systems PO Box Magdeburg Germany ADBIS - DASFAA 2000 SYMPOSIUM September 5 - 8, 2000

Eike Schallehn Martin Endig Kai-Uwe Sattler 2 ADBIS - DASFAA 2000 SYMPOSIUM Overview Introduction Specific requirements General overview of the approach Source descriptions XML adapter Special application: Citation Linking Conclusion and outlook

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 3 ADBIS - DASFAA 2000 SYMPOSIUM Introduction Integration of bibliographical metadata: author, title, publisher, citations,... Wide range of existing providers –Specific for research or geographical area –Publishers, libraries, resellers –differ in scope, quality and quantity of maintained data Problems for users –Knowledge about locality, scope, quality etc. is required Goal: single point of access

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 4 ADBIS - DASFAA 2000 SYMPOSIUM General Overview (1) Federation Layer Adapter/Source Layer... Adapter Higher-level services Single Point of Access Federation Service DBLP Application Layer Publisher: Springer Publisher: Spektrum DB N

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 5 ADBIS - DASFAA 2000 SYMPOSIUM General Overview (2) non-cooperative providers: –WWW databases –Z39.50 sources cooperative providers: –Databases (Relational, O-R, etc.) –sources with limited query facilities capable of providing XML Adapters for certain classes of providers

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 6 ADBIS - DASFAA 2000 SYMPOSIUM Special Requirements (1) Efficient acces for global applications: –Object-relational conforming to standards –flexible import and integration regarding great numbers of constantly changing systems Minimal provider-side resource consumption: –limited query facilities often exist –additional functionality constrained by local resources Assumption: common interest in cooperation (on a certain level)

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 7 ADBIS - DASFAA 2000 SYMPOSIUM Special Requirements (2) Efficient transfer: –usage of XML as transfer standard –size of intermediate results critical factor for possibly slow network connection –move queries with high selectivity to the source Minimal provider-side implementation efforts: –only wrapping of existing functionality required –tools for design based on source description –XML can easily be created

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 8 ADBIS - DASFAA 2000 SYMPOSIUM Source Description (1) Access to local sources mainly depends on their query capabilities Global query re-writing and query processing based on these information Example: WWW-databases –Constant selections –Set of allowed comparison operators per attribute –simple combinations Ô Corresponding description required

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 9 ADBIS - DASFAA 2000 SYMPOSIUM Source Description (2) Example: Source 1 exports a relation BookStore and allows equality match for author and title, and either separate usage or a simple combination alter table BookStore set query contraints ( predicates ((authors,=),(title,=)), combinations((author),(title),(author,title)) ); Example continued: Source 2 exports a relation Books and allows only equality match on title 

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 10 ADBIS - DASFAA 2000 SYMPOSIUM Source Description (3) (BookStore) (Books) select * from Publications where title=´ODBMS´ and authors=´Saake´ or authors=´Heuer´;

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 11 ADBIS - DASFAA 2000 SYMPOSIUM XML Adapter (1) XML for transfer of bibliographical metadata –Cooperative providers –Provider-specific DTD –Underlying data management may vary Ü Transformation to object-relational structures Application of XSLT –Intermediate step: Transformation to internal DOM representation according to own DTD –Design of XSLT mapping supported by tools Further result and query processing at federation layer

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 12 ADBIS - DASFAA 2000 SYMPOSIUM XML Adapter (2) select * from Publications where title like ´ODBMS´; 1 ODBMS Heuer, A.... Example Query: Possible XML Result:

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 13 ADBIS - DASFAA 2000 SYMPOSIUM XML Adapter (3) Source Description XSLT F RA QL Query Processor XML Query Evaluator... Query Translator XML Parser Result Translator...

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 14 ADBIS - DASFAA 2000 SYMPOSIUM Application: Citation Linking Integrating citation information from various sources:

September 5 - 8, 2000 Eike Schallehn Martin Endig Kai-Uwe Sattler 15 ADBIS - DASFAA 2000 SYMPOSIUM Conclusion and Outlook Application of concepts known from the area of federated and mediator-based systems Focus on adapter for partially cooperative providers of bibliographical data –Description of query capabilities for efficient distributed query processing –Result transfer based on XML –Result transformation based on XSLT Better tool support Improve identification of same-objects