OGSA Workshop, March 2002 MetaData Group

What metadata are needed? AIM: Systematic metadata framework for Grid Are these explicitly catered for in OGSA? A global Grid must manage different world views

Ontologies Affect web service communications Particularly critical when automating interactions with Grid Which services are available for task x given y? search UDDI register Matching service/partial service/similar service? W3COGSA

Ontological services Metadata terms defined with reference to particular ontologies football (ontology 21, USA) football (ontology 53, Australia) football (ontology 67, Great Britain) Ontologies defined using languages such as OWL: –lattices of relationships, non-hierarchical –ability to combine terms (e.g. sheep + body + weight) Semantic Web

OR W3C OGSA W3C OGSA W3C OGSA document

W3C OGSA W3C OGSA document

Metadata (1) General information about services (model +/or data) –What does it do; –Contact details; –Who designed the service and when; –Reference to scientific documents UDDI + semantic enrichment User invokes personal metadata for inference re quality, reliability Corporate

Metadata (2) Detailed info re services –Input & output structures or formats required (needs to match available data) –Quality of service performance based on history etc. –Average expected run/delivery times –[Quality & accuracy statements, which algorithms, parameters etc.] Users: Provenance, quality, accuracy, reliability, timeliness WSDL + enrichment

Metadata (3) Individual service instances (1) –length of run –cost –means of specifying workflow apriori for compound services –Audit trails: which service/data sub-components have been invoked? Users: Provenance, quality, simplicity Notions of stateSemantic, enriched web

Metadata (4) Individual service instances (2) –Into which units has a problem been decomposed? –Scheduling –Run history (time, machines) –... Notions of stateSemantic, enriched Web Users: Abstract notions, to be hidden

Metadata: summary Widespread dissemination of planned readable document clarifying OGSA is required (Ladybird Book of OGSA); Development of ontological services will be vital as we move from web services to global, automated Grid services; Future emphasis on the notion of state both in relation to OGSA generally and also to metadata is required.