WP2 Deliverable 4.3 Views and Structured Querying in Self e-Learning Networks

Self e-Learning Networks (SeLeNes) aim at facilitating access to digital material — not necessarily primarily produced for educative purposes — to a wide audience of learners and instructors with diverse educational background and requirements. One step towards this goal is the ability to specify educational needs or to describe educational material according to personalized e-learning terminologies and conceptualisations. In this deliverable we investigate how this goal can be achieved in a declarative way using language primitives for defining views over distributed, autonomous RDF bases holding learning object descriptions and schemas. Based on these primitives, we introduce a fully-fledged view definition language, called RVL, for creating not only virtual resource descriptions, but also virtual RDF/S schemas from (meta)classes, properties, and resource descriptions available on a SeLeNe. Furthermore, we illustrate how RVL views can be composed with structured RDF/S queries expressed in a query language like RQL, by means of an internal logical framework (linear Datalog rules) capturing the semantics of the RDF/S model, as well as of RQL queries and RVL views. To the best of our knowledge, RVL is the first declarative view definition language offering such functionality. Finally, we present how the RQL/RVL query processing can be implemented in three different architectural alternatives: the centralized, the mediated and the autonomic scenarios as presented in Deliverable 5.

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