Describing OGC WMS and WFS with the OWL-S Web Service Ontology - PowerPoint PPT Presentation

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Describing OGC WMS and WFS with the OWL-S Web Service Ontology

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Describing OGC WMS and WFS with the OWL-S Web Service Ontology. ... Augment with semantic links. ... OWL-S can be used to support discovery and execution. – PowerPoint PPT presentation

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Title: Describing OGC WMS and WFS with the OWL-S Web Service Ontology


1
Describing OGC WMS and WFS with the OWL-S Web
Service Ontology
  • Dr Kristin Stock
  • Allworlds Geothinking, UK
  • Centre for Geospatial Science, University of
    Nottingham, UK
  • EDINA, UK

2
Introduction
  • COMPASS Project (http//compass.edina.ac.uk/)
  • OGC Standards focus on syntactic descriptions of
    web services.
  • Some recent work incorporates object semantics.
  • Nothing so far done on semantics of
    functionality.
  • We tried to fill this gap with OWL-S.

3
Why do this?
  • Web service ontologies are intended to assist
    with
  • Discovery
  • Dynamic execution
  • Chaining
  • Automating the publish-find-bind model.

4
OWL-S
  • One of the dominant web service ontologies (cf
    WSMO).
  • The basic model
  • Profile advertises what the service does
  • Process Model describes the process that it
    executes
  • Grounding describes how it can be executed.
  • Inputs, Outputs, Preconditions, Results

5
ServiceProfile
Inputs, Outputs, Preconditions and Results
presents (what it does)
ServiceGrounding
Domain Ontology (Feature Types)
Service
supports (how to access it)
describedBy (how it works)
ServiceModel
Inputs, Outputs, Preconditions and Results
6
GetCapabilities
  • Content of GetCapabilities mapped to OWL-S.
  • This process could be automated for WFS and WMS.
  • Augment with semantic links.

7
The OWL-S OGC Ontology (1)
  • Created an OWL-S OGC Ontology to describe the
    specifications.
  • Each implementation of a WFS or WMS imports the
    OWL-S OGC Ontology and creates instances.

8
The OWL-S OGC Ontology (2)
  • For WFS and WMS, the OWL-S OGC Ontology is quite
    comprehensive, because specs are specific
    wouldnt be so for WPS.

9
OWL-S OGC Ontology Whats in it?
  • Classes for
  • WFS and WMS specialised service
  • The processes that a WMS or WFS may offer and
    inputs and outputs
  • An OGCHttp Grounding and operations
  • Connections between processes and the operations
    that implement them.

10
The Grounding
  • OWL-S has a WSDL grounding.
  • We didnt use it because its XML, not OWL
    doesnt fit our architecture.
  • Could have applied the WSDL RDF mapping but
    time limited.
  • Created a new grounding.

11
Children of ProcessAtomicProcess (for each WFS
and WMS operation)
OGCHttpGrounding
groundsAtomicProcess
hasOGCHttpOperation
OGCHttpOperation
hasltOperationNamegtInput hasltOperationNamegtOutput
hasOGCHttpConstraint
hasOGCHttpParameter
OGCHttpParameter
OGCHttpConstraint
ProcessParameter
groundsAbstractParameter
hasQueryModel
hasDomain
hasDomain
Domain
QueryModel
hasComponent
Meaning
CheckBox
RadioButton
isA
DataType
PossibleValues
InputBox
OptionList
DefaultValue
DomainMetadata
ValuesUnit
12
How exactly does this describe the semantics?
  • IOPR describe semantics of functionality
  • Process describes steps/branches/loops etc. (not
    implemented)
  • IOPR can be connected to concepts in a domain
    ontology
  • OWL-S OGC ontology includes hasTopic to link
    service, feature type or layer.

13
Dynamic service execution
  • Grounding includes binding between operation
    parameters and query model.
  • This is information that can be used to
    dynamically generate form to ask user for input.
  • e.g. Which feature type they would like to query
    in WFS, layer in WMS.

14
Whats in the ontology for each web service?
  • Details from GetCapabilities, including
  • Which operations are implemented
  • Actual grounding (URLs) and query model
  • etc.
  • Semantic hasTopic links
  • You dont have to repeat IOPR.

15
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16
What did we find?
  • Its very cumbersome.
  • Full implementation of OWL-S includes IOPR more
    than once (different purposes)
  • Difficulties with cardinality constraints.

17
How did we modify OWL-S?
  • Did not describe IOPR multiple times, but once
    with references, same for parameters.
  • New grounding.
  • Did not define IOPR in each instance ontology,
    just referenced.

18
Its a limited implementation
  • Didnt fully describe preconditions and results.
  • Didnt fully model the complexity of some
    parameters.
  • Process model limited.

19
Conclusions
  • Full OWL-S implementation impractical.
  • OGC specifications make it easier to use OWL-S.
  • OWL-S can be used to support discovery and
    execution.
  • Didnt test orchestration.

20
Questions or Comments?
  • or contact me
  • kristin.stock_at_nottingham.ac.uk
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