Query Processing in ROSA Data Model

Learning Content Management Systems (LCMS) store and manage e-learning content and play an important role in the development of Distance Learning technology. ROSA (Repository of Objects with Semantic Access) is a LCMS that provides the creation, storage, reuse, retrieval and management of learning objects (LO). In ROSA, course structure and content (LOs) are organized according to Conceptual Maps. The latter expresses semantic relationships among LOs through labeled associations, such as: prerequisite, is_basis_for, fundaments etc. This paper presents ROSA data model and focuses on the query processing on top of this model. An algebra language is presented, the ROSA algebra, with operations on LOs metadata and navigation through semantic relationships among LOs. Some equivalence rules are also presented opening the space for query transformations. Finally, a query execution engine that implements ROSA algebra and processes queries over conceptual maps is presented. This work suggests a bridge between database query processing techniques and the Semantic Web through its application to the e-learning domain.