Knowledge representation and reuse on the WWW: conventions, RDF extentions and simple notations

The Resource Description Framework (RDF) provides a low-level general model to describe relationships between objects. Its ultimate goal is to permit the representation, combination and processing of most kinds of metadata or knowledge from Web-accessible documents or databases. Metadata resources can then be processed for information retrieval, filtering, personalizing, aggregation or management. However, apart from simple metadata, representing knowledge with the low-level RDF model and its verbose syntax in XML (RDF/XML) is difficult. The process implies many choices in the representation of common logical/semantic notions, e.g. those related to variables, sets, negation and contexts. If an agent (person or software) does not follow the same conventions as another, representions will hardly be comparable, mergeable and retrievable. The same conclusion applies for the ontological choices (and to a lesser extent the lexical choices) an RDF/XML author is faced with. In this paper we synthesize lexical, logical and ontological conventions from various knowledge representation projects, and when necessary, extend RDF/XML so that additional constructs can be represented. We also propose two high-level and expressive textual notations Frame-CG and Formalised English to allow users to rapidly represent knowledge. These notations may then be automatically translated into RDF/XML. Such conventions and notations seem to us a necessary step to permit knowledge representation and reuse by a large number of people and thus support the "semantic Web" [Berners-Lee et al., 1999] for which RDF was created.