Philipp Kärger

Integrating learning object repositories using a mediator architecture

We propose a mediator architecture that allows a learning system to retrieve learning objects from heterogeneous repositories. 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, a novel ontology-based query-rewriting method has been developed. The architecture has been realized in the Web-based, user-adaptive and interactive e-learning environment ActiveMath. Currently, it enables the ActiveMaths course planner to access four heterogeneous learning object repositories.

Services for Knowledge Resource Sharing & Management in an Open Source Infrastructure for Lifelong Competence Development

Access to learning information is still restricted due to the lack of technical and semantic interoperability, locking knowledge resources in disconnected islands. This situation does not provide learners with a motivating environment in which to access and share learning information. In order to target emerging needs for lifelong competence development, a flexible and open source environment for management and sharing of knowledge resources must be built on top of an infrastructure that maximizes the amount of information available, therefore integrating centralised repositories and user desktop resources as well as emergent Web 2.0 applications. This paper describes the challenges and requirements that need to be addressed and presents a set of interfaces and our current implementation of the knowledge resource sharing and management service oriented architecture.

Querying Heterogeneous and Distributed Learning Object Repositories via Ontology-Based Mediation

1We 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 Active Math.