Distributed and Grid Computing Research Group A Grid Service Discovery Matchmaker based on Ontology Description written by Simone A. Ludwig and Peter van Santen EuroWeb 2002 Conference Oxford 17./18. December 2002 Simone Ludwig Distributed and Grid Computing Research Group Brunel University

Acknowledgement Work was funded by PPARC (Particle Physics and Astronomy Research Council, UK) for the IST Program DataTAG, European Union (Grant IST-2001-32459).

Outline Service Discovery Problem Ontology Criteria for Matching Mechanism Components Description of the Framework Framework Conclusions

Service Discovery Problem Service Discovery Survey showed the two problems Service Discovery System face: Lack of description languages Lack of inexact matches Solution: XML as a descriptive language Usage of Ontologies Jini, Service Location Protocol (SLP), Universal Plug and Play (UPnP), Salutation, CORBA Trader Service and Web Service Discovery with UDDI, ebXML and WS-Inspection

Ontology What is an ontology? Ontology provides: An ontology is about a shared understanding of some domain of interest. Ontology provides: Interoperability Knowledge sharing & reuse

Why is Ontology important for service discovery? Term ontology is useful in the context, where it describes the need for the provider of a service and the user of that service to share a common understanding of what capabilities the service offers and how they can be put to use.

History about Ontology RDF(S) (Resource Description Framework Schema) is an ontology/knowledge representation language To allow automated reasoning: OIL (Ontology Inference Layer) DAML+OIL (DARPA's Agent Markup Language) Ontology of Services: DAML-S

Service Ontology – DAML-S Resource Service Service Profile Service Model Service Grounding description functionalities functional attributes provides presents describedBy supports How to access it What it does How it works

Service Discovery Interactions SD Matchmaker Service Requester Service Provider Invoke Publish Query Grid Application Grid Service

Matchmaking Mechanism Matchmaking mechanism should satisfy the following requirements: The matching engine should support flexible semantic matching between advertisements and requests on the basis of the ontology available. The matching engine should encourage providers and requesters to be precise with their descriptions at the cost of paying the price of either not being matched or being matched inappropriately. The matching process should be efficient which means that it should not burden the requester with excessive delays that would prevent its effectiveness.

Components of Service Discovery Framework Service Requesters Grid Applications Service Providers Grid Services Service Matchmaker Registry Knowledge-Base: ontology semantics with DAML-S Reasoning engine Based on LARKS Matchmaker -> Provides close matches

Service Discovery Framework Service Registry DB Service Requester Grid Application Parser Context Matching Semantic Matching Service Ontology DB Auxiliary DB Concept Word Distance, Type Hierarchy Advertisement Domain Ontology Service Provider Grid Service Syntactic Matching Service Discovery Matchmaker Task Ontology Ontology Reasoner 1. 2. 3. 4.

Service Discovery Process The Service Provider (SP) registers its service description in the Service Matchmaker (SM). The Service Requester (SR) requests a service and sends the request to the Service Discovery Matchmaker. The SDM returns the matches to the SR. The SR decides then which service to use depending on the client’s need.

How does the Framework fulfil the matching criteria? Supports flexible semantic matches between advertisements and requests -> Ontology Preciseness of the description -> DAML-S based on XML No excessive delays -> Well-defined Ontology

Conclusions Ontology is very useful to describe services effectively. Service Discovery Matchmaking Framework based on ontology descriptions allows for a better Service Discovery Process.