1. Languages on the Semantic Web Frank van Harmelen Vrije Universiteit Amsterdam Ian Horrocks University of Manchester

2. Currently in place: XML: l interchange syntax, no semantics RDF: l datamodel, some semantics & inference (recent!) RDF Schema: l concept modelling, more semantics & inference DAML+OIL: l more expressive ontology language; l quite expressive; expensive inference

3. Stack of languages:

4. Extensions (by popular request) Query language l (RQL, DQL, RDQL, XQL) Rule language l (RuleML initiative, DAML+OIL) Modularity concept l (more than namespaces) Human readable syntax l ( RDF) Non-logical structure l ( logical equivalence)

5. Higher levels in the stack Language for writing down proofs Notions of trust Current danger split between XML & RDF Conclusion Roadmap clear danger of split