Querying Learning Object Repositories via Ontology-Based Mediation

Philipp Kärger, Carsten Ullrich, Erica Melis

In: Kinshuk, Rob Kopers, Piet Kommers, Paul Kirschner, Demetrios G. Sampson, Wim Didderen (editor). Proceedings of the The 6th IEEE International Conference on Advanced Learning Technologies. IEEE International Conference on Advanced Learning Technologies (ICALT) Pages 845-846 IEEE Computer Society 7/2006.


We propose a mediator architecture that allows a learning system to retrieve learning objects (LOs) from heterogeneous repositories of LOs and not exclusively from its proprietary repository. A mediating component accepts queries formulated in a uniform query language, translates them into repository specific queries and passes them to each connected repository. For the translation of queries, an ontology-based queryrewriting method has been developed which uses the specified knowledge representation of the repository and an ontology mapping to compute the rewriting steps for translating. For distributing queries we realized a mediating architecture, which passes the translated queries to the repositories. This architecture has been integrated in the Web-based, user-adaptive and interactive e-learning environment ActiveMath. Currently, it enables the ActiveMath's course planner to access four heterogeneous LO repositories. The course planning component can create courses adapted to the learner's goals, knowledge, learning behaviour and a specific learning scenario. To select adequate LOs, the course planner initially queried its proprietary repository MBase for LOs. The challenge our architecture faces is to integrate more than one repository into ActiveMath's course generation. Currently, with the help of the architecture here-proposed, the course planner retrieves LOs additionally from the repository of the DaMiT-system, of the MathsThesaurus, and the LeActiveMath ExerciseRepository.

German Research Center for Artificial Intelligence
Deutsches Forschungszentrum für Künstliche Intelligenz