1. 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

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

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

4. 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

5. 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

6. 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.

7. 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

8. 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

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

10. 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.

11. 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

12. 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.

13. 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.

14. 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

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