1. 26/02/2004 1 WSMO – UDDI Semantics Review Taxonomies and Value Sets Discussion Paper Max Voskob (mvoskob@msi.net.nz) – February 2004 UDDI Spec TC V4 Requirements Taxonomy Support for Semantics Max Voskob (mvoskob@msi.net.nz) – February 2004 Presenter: Matt Moran, NUIG-DERI, 16 Feb 2004

2. 26/02/2004 2 WSMO – UDDI Semantics Review Taxonomies and Value Sets - Discussion Overview – Enabling UDDI to use metadata with external knowledge will allow UDDI registries to align with Semantic Web technologies Four Scenarios – Ontology points to UDDI – UDDI points to Ontology – RDF-bag points to Ontology – UDDI Value set points to Ontology

3. 26/02/2004 3 WSMO – UDDI Semantics Review Scenario 1: Ontology points to UDDI Issues - Tight coupling of UDDI to ontology - UDDI must understand ontology or use an external provider for validation Benefits - Reasoning engine can work directly with ontology without UDDI Description - Category bag key identifies the ontology - Name points to the unique concept ID in the ontology - Value may provide the key of a related UDDI entity Issues - Validation as in scenario 1 - Hard to describe many-to-many or even one-to-many relationships Scenario 2: UDDI points to Ontology

4. 26/02/2004 4 WSMO – UDDI Semantics Review Scenario 3: RDF-Bag points to Ontology Description - UDDI has additional RDF bag next to category and identifier bags - RDF statements can be free or follow an RDFS schema Issues - UDDI must understand RDF - RDF query language may be required - Validation as in scenarios 1 and 2 Benefits - Rich metadata with every UDDI entity - Any standard can be used for ontology as long as consistent with Sem Web Description - Ontology owner provides a value set corresponding to ont. - UDDI uses value set for syntax and value validation - Key-name-value triples link to concepts in the ontology Issues - Information loss in transformation to value set - Maintenance of value set over time very awkward Scenario 4: Value Set points to Ontology

5. 26/02/2004 5 WSMO – UDDI Semantics Review Part 2: Taxonomy Support for Semantics Overview – Current UDDI categorisbnation is limited to value sets and direct value matching – This document proposes adding an RDF bag to UDDI to enable the use of ontologies for search Three Scenarios – Find entity by browsing the Ontology – Find entity using semantic engine (ext. or int.) – A combination of the first two scenarios

6. 26/02/2004 6 WSMO – UDDI Semantics Review Scenario 1: Find entity – Browse Ontology - Search ontology to find UDDI categories - Find entities in UDDI based on these categories - Ask UDDI server for related categories. It does this by invoking an internal or external inference engine Scenario 2: Find entity – Search (Internal Semantic Engine)

7. 26/02/2004 7 WSMO – UDDI Semantics Review Scenario 2b: Find entity – Search (External Semantic Engine)

8. 26/02/2004 8 WSMO – UDDI Semantics Review Scenario 3: Find entity – combined browsing and searching

9. 26/02/2004 9 WSMO – UDDI Semantics Review Requirements Ontology format – any RDF compatible UDDI Client should be able to: – Locate ontologies with a particular UDDI server – Browse ontologies – Use ontologies to specify search criteria RDF Bag – Checked or unchecked – If checked must be able to validate syntactically and semantically – Can be attached to any UDDI entity with category/id bags

10. 26/02/2004 10 WSMO – UDDI Semantics Review UDDI Changes – Use Cases Entity owner prepares an RDF Bag Ontology owner creates and maintains ontology UDDI syntactically and semantically validates RDF Bag User or agent uses ontology to search UDDI using RDF Bag UDDI Changes – New Structures New bag for metadata described by RDFS or XSD

11. 26/02/2004 11 WSMO – UDDI Semantics Review Issues Inference Engines – Who will provide them? Syntactical validation requires understanding of RDFS or XSD Semantic validation requires a standardised API between inference engine and the UDDI client Semantic validation can be prohibitively expensive RDF Querying – no winner language RDF-Bag use RDF or XML? RDFS or XSD for syntactic validation or both? What ontology language – OWL preferred