EU-NSF Working Group on Interoperability between Digital Libraries
by Daniel L. Kiskis and Uwe Röhm
The first joint meeting of the working group on Interoperability between Digital Library Systems took place 10-11 February 1998 at ETH Zurich, Switzerland. The purpose of this meeting was to exchange ideas and opinions between the working group members and to generate a report on future research directions on interoperability between digital libraries.
The Interoperability working group assembles researchers from digital library systems and database and information systems. The US part, lead by William P. Birmingham (University of Michigan), is formed of Barry Leiner (MCC), Andreas Paepcke (Stanford University), Daniel Kiskis (University of Michigan), and Steve Ketchpel (Stanford University). The European side is represented by Vassilis Christophides (FORTH), Sophie Cluet (INRIA), Panos Constantoupoulos (FORTH), Sverker Janson (SICS), Olle Olsson (SICS), Fausto Rabitti (CNR), and Carlo Meghini (CNR), and is lead by Hans-Jörg Schek (ETH Zurich). In addition to the attending members, guest talks were given by Klemens Böhm (GMD/ETHZ) and Moira Norrie (ETH Zurich).
This working group exists in conjunction with working groups in Metadata, Intellectual Property Rights and Economics, Resource Indexing and Discovery in a Globally Distributed Digital Library, and Multilingual Information Access. Recognizing the interoperability issues inherent in each of these other groups, our group focussed on the architecture which would integrate these areas. Drawing from a number of sources, including the ARPA I3 Reference Architecture, the University of Michigan Digital Library agent architecture, and the Stanford InfoBus architecture, the group proposes an architecture which broadly divides the system into clients, mediators, and servers. Within this architecture, four indicative themes of research were identified:
- Information Model: We will investigate a model of information which includes structure, semantics, and services. The description language based on the model should have an ontological basis for maximum flexibility and inter-operability. Another area of research is the dynamic creation of documents views on databases to facilitate information retrieval and vice-versa.
- Coordination and Control: As much as possible, the mechanisms for providing digital library services should be transparent to the user. To achieve this, mediators must be able to autonomously negotiate for digital library services and make commitments for query and result manipulation. Because dependencies will exist between mediators and the information they manage, transactional execution guarantees should be taken into account. A flexible way of achieving this is via spheres of atomicity and isolation.
- Query Processing: Rich query mani-pulation and processing mechanisms must be developed. To understand the why and how of a query result, users should have the possibility to interact with the query processing. This includes both controlling query formulation and using relevance feedback techniques. A promising way seems to be the integration of indexing and retrieval mechanisms developed for multimedia databases with access methods for traditional databases.
- Implementation Mechanisms: Different collections and DL services are accessible using different protocols. They accept different query formats and return results in different formats. Translation or wrapping of these service-specific aspects should be done as close to the source as possible. Between mediators, we should use a single, rich, object-oriented communi-cation mechanism, such as CORBA. In addition to defining these translators and wrappers, we must also explore how best to utilize the native CORBA services in order to provide the other capabilities required by the digital library.
The group is currently working on a research report on the mentioned topics, which will include the presentations given during the Zurich meeting. Further information, eg about scheduled meetings, will be available on the public web page of the working group at http://www.si.umich.edu/UMDL/EU_Grant/interop/interop.htm
William Birmingham University of Michigan
Hans-Jörg Schek ETH Zurich