The myGrid approach for

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• The myGrid approach for
• attaching semantic annotations
• to service descriptions
• Luc Moreau
• University of Southampton,UK

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Overview

• Motivation
• Existing technologies and limitations
• Metadata attachment
• The Southampton Service Directory
• Conclusion

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Overview

• Motivation
• Existing technologies and limitations
• Metadata attachment
• The Southampton Service Directory
• Conclusion

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Service Discovery

• Service discovery is a difficult task in large
  scale, open distributed systems such as the Grid
  and Web, due to the potentially large number of
  services advertised.
• In order to filter out the most suitable
  services, many have advocated the use of semantic
  descriptions of services in a manner that is
  amenable to automatic processing Berners-Lee,
  Hendler, Lassila 2001, damls-iswc02
• AHM03 myGrid and service discovery talks

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Semantic Discovery

• Semantic discovery is the process of discovering
  services capable of meaningful inter-operability,
  even though the languages or structures with
  which they are described may be different.
• Typically, a semantic discovery process relies on
  semantic annotations, containing high-level
  abstract descriptions of service requirements and
  behaviour.
• This presentation focuses on the means to
  register and discover services according to such
  semantic annotations.

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Metadata (for the provider)

• An essential element in semantic discovery is to
  allow users to augment service descriptions with
  additional information, i.e. metadata.
• Providers may adopt various ways of describing
  their services, access policies, contract
  negotiation details etc.

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Metadata (for the consumer)

• Resource consumers can also impose their own
  selection policies on the services they prefer to
  utilise
• provenance,
• derived quality service,
• reputation metrics etc.
• We want a system that allows multiple users (not
  just publishers) to add metadata to service
  descriptions.

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Metadata about what?

• It is useful to add metadata to
• Service descriptions, and
• Any other concept that may influence the
  discovery process, e.g.
• supported operations,
• types of arguments,
• businesses,
• users.

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Structured vs. unstructured

• Metadata may be structured according to published
  ontologies, so that it can be interpreted
  unambiguously by multiple users, especially in
  the case of a public registry.
• Alternatively, metadata may also be raw and
  unstructured, in the case of a personal registry
  used by a single user.

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Overview

• Motivation
• Existing technologies and limitations
• Metadata attachment
• The Southampton Service Directory
• Conclusion

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A typical UDDI service registration

• Name
• Key
• Location
• WSDL interface

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A textual representation of a service description
in UDDI
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UDDI Limitations

• The interface (describe as a WSDL file) is
  referred to by a UDDI construct called TModel,
  and is not contained in the UDDI registration
  itself. Still true with the new TN which does not
  cover a port type content.
• Similarly, TModels can also be used to refer to
  external classifications.
• In conclusion, in UDDI, there is no uniform way
  of querying about services, their interfaces and
  their classifications.

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A typical abstract WSDL interface

• Set of port types
• Set of operations
• Set of messages and their message parts

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• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltwsdldefinitions targetNamespace"http//www.ebi
  .ac.uk//alignmentblastn_ncbiderived"
  xmlns"http//schemas.xmlsoap.org/wsdl/"
  xmlnswsdl"http//schemas.xmlsoap.org/wsdl/"gt
• ltwsdlmessage name"runRequest1"gt 
• ltwsdlpart name"in0" type"xsdstring" /gt  
• ltwsdlpart name"in1" type"xsdstring" /gt  
• lt/wsdlmessagegt 
• ltwsdlmessage name"runResponse1" /gt
• ltwsdlportType name"AnalysisWSAppLabImpl"gt
• ltwsdloperation name"run" parameterOrder"in0
  in1"gt 
• ltwsdlinput message"implrunRequest1"
  name"runRequest1" /gt  
• ltwsdloutput message"implrunResponse1"
  name"runResponse1" /gt  
• ltwsdlfault message"implSoaplabException"
  name"SoaplabException"/gt
• lt/wsdloperationgt 
• lt/wsdlportTypegt 
• lt/wsdldefinitionsgt

Excerpt from an EBI sequence alignment service
interface
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• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltwsdldefinitions targetNamespace"http//www.ebi
  .ac.uk//alignmentblastn_ncbiderived"
  xmlns"http//schemas.xmlsoap.org/wsdl/"
  xmlnswsdl"http//schemas.xmlsoap.org/wsdl/"gt
• ltwsdlmessage name"runRequest1"gt 
• ltwsdlpart name"in0" type"xsdstring" /gt  
• ltwsdlpart name"in1" type"xsdstring" /gt  
• lt/wsdlmessagegt 
• ltwsdlmessage name"runResponse1" /gt
• ltwsdlportType name"AnalysisWSAppLabImpl"gt
• ltwsdloperation name"run" parameterOrder"in0
  in1"gt 
• ltwsdlinput message"implrunRequest1"
  name"runRequest1" /gt  
• ltwsdloutput message"implrunResponse1"
  name"runResponse1" /gt  
• ltwsdlfault message"implSoaplabException"
  name"SoaplabException"/gt
• lt/wsdloperationgt 
• lt/wsdlportTypegt 
• lt/wsdldefinitionsgt

Inputs Details
No information about the meaning of these strings!
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WSDL Limitations

• Syntactic type string is meant to denote a
  nucleotide sequence data (multiple formats
  supported).
• WSDL does not allow to distinguish the type
  required at the transport layer from the meaning
  of the data.
• In conclusion, WSDL is limited to XSD types and
  does not distinguish syntactic and semantic types.

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Other Approaches

• BioMoby provides some semantic description for
  atomic services
• DAML-S supports semantic descriptions of
  services, but attachment mechanism is convoluted
  since it involves DAML-S profile, grounding and
  process.
• No direct integration with UDDI standard.

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Overview

• Motivation
• Existing technologies and limitations
• Metadata attachment
• The Southampton Service Directory
• Conclusion

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Metadata Attachment

• The capability to attach an arbitrary piece of
  information as a metadata to an entity of a
  service description.
• Metadata can be structured or not.
• Metadata can be used in queries.
• Should contain provenance information (date,
  author)

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Attaching Ratings to Services
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Registering myGrid services
myGrid services are characterised by the
following profile

• performs_task e.g. retrieving
• uses_resource e.g. SWISS PROT protein database
• is_function_of e.g. software tool used, e.g.
  BLAST
• uses_method e.g. algorithm used

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Attaching metadata to arguments
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• ltwsdldefinitions targetNamespace"http//www.ebi
  .ac.uk/alignmentblastn_ncbiderived" gt
• ltwsdlmessage name"runRequest1"gt 
• ltwsdlpart name"in0" type"xsdstring" /gt  
• ltwsdlpart name"in1" type"xsdstring" /gt  
• lt/wsdlmessagegt 

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Argument semantic type
rdf_3 a ltwsdlMessagegt
ltwsdlhasQNamegt a ltwsdlQNamegt
ltwsdlhasNameSpacegt "http//www.ebi.ac.uk/align
mentblastn_ncbiderived"
ltwsdlhasLocalNamegt "runRequest1"
ltwsdlhasMessagePartgt rdf_1
a ltwsdlMessagePartgt
ltwsdlhasNamegt "in0"
ltwsdlhasTypeNamegt a
ltwsdlQNamegt
ltwsdlhasNameSpacegt "http//schemas.xmls
oap.org/xsd/"
ltwsdlhasLocalNamegt "string"
ltuddihasMetadatagt a
ltmygridsemantic_typegt
ltuddihasDategt "Fri Aug 22 111229
BST 2003" rdfvalue
ltmygrid2nucleotide_sequence_datagt
ltuddihasAuthorgt "Luc Moreau"
...

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Overview

• Motivation
• Existing technologies and limitations
• Metadata attachment
• The Southampton Service Directory
• Conclusion

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Class diagram
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Publishing Metadata
// Business service. MetadataInfo
addMetadataToBusinessService (String serviceKey,
Metadata metadata) // Business entity.
MetadataInfo addMetadataToBusinessEntity (String
businessKey, Metadata metadata) // Message part
MetadataInfo addMetadataToMessagePart (String
messageNamespace, String messageName, String
partName, Metadata metadata)
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Extending UDDI api
ServiceList findService (String
businessKey, Vector names, CategoryBag
categoryBag, TModelBag tModelBag, FindQuali
fiers findQualifiers, MetadataInfoBag
metadataInfoBag, int maxRows)
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Southampton Service Directory

• Information stored in triple store, uniform
  queries through RDQL interface
• Full compatibility with UDDI v2, WSDL
• Attachment of metadata
• Simple DAML-S matchmaker and BioMoby-like
  convenience API.

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Overview

• Motivation
• Existing technologies and limitations
• Metadata Attachment
• The Southampton Service Directory
• Conclusion

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Conclusion

• Service is hosted as a Web Service, to be
  migrated to an OGSA service
• Integrated with Manchesters semantic reasoning
  engine
• How to support other APIs (Grid MDS or OGSA
  compatibility)
• Next our focus will be on management policies

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Acknowledgment

• Simon Miles, Juri Papay, Keith Decker, Terry
  Payne, Michael Luck, David DeRoure,S John
  Dickman, Claudia di Napoli, Richard Lawley,
  Ananth Krishna, Victor Tan
• Carole Goble, Philip Lord, Chris Wroe, Robert
  Stevens
• The myGrid consortium
• myGrid industrial collaborators

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www.mygrid.org.uk
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