Knowledge Representation and Query in Semantic MediaWiki: A Formal Study

Semantic wikis extend conventional wikis, which allow users to collaboratively generate data, through semantic web technologies. This allows wiki-based information to be annotated with metadata for facilitating automated search, querying, propagation and inference. Se- mantic wikis have recently attained wide adoption and, with this, formal research on their functionality (e.g., inference and concept modeling) is starting to be conducted. In this paper, we present a formal analysis of the semantic technologies in an emerging semantic wiki framework called Semantic MediaWiki (SMW). In particular, we deflne a RDF- like model theoretical semantics for the SMW modeling language, and a closed world, minimal Herbrand model semantics for the SMW query language by a reduction to positive logic programs. We discover that the entailment problem in SMW is NL-complete thus is highly tractable, and query answering in SMW is P-complete in general and is in L if subqueries are disallowed. We show that such a formalization allows us to discover some rather powerful usages of SMW, such as entailment in- ference, and to extend SMW with some frequently needed features, like negation as failure.