Knowledge Representation for the Distributed, Social SemanticWeb - Named Graphs, Graph Roles and Views in NRL

The vision of the Semantic Web mainly aims at scenarios with multiple, distributed and autonomous information providers and consumers. However, the current standards for knowledge representa- tion mainly see the Semantic Web as one big knowledge base without explicitly acknowledging the distributed, social nature of knowledge in the technological basics. Originally coming from the specific requirements of the idea of a So- cial Semantic Desktop, we identified two questions as being fundamental also for the general Semantic Web endeavor: i) How can we cope with the heterogeneity of knowledge models and ontologies, esp. multiple knowl- edge modules with potentially different interpretations? ii) How can we support the tailoring of ontologies towards different needs in various ex- ploiting applications? In this paper, we present the NEPOMUK Representational Language (NRL), an approach to tackle these two question that is based on named graphs for the modularization aspect and a view concept for the tailoring of ontologies. This view concept turned out to be of additional value, as it also provides a mechanism to impose different semantics on the same syntactical structure. In addition to the general construction of NRL we describe our first im- plementations on top of a standard Semantic Web representation frame- work, Sesame2. A first benchmark of this implementation shows that the level performance can be acceptable to many Semantic Web developers.