Title: Describing OGC WMS and WFS with the OWL-S Web Service Ontology
1Describing 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
2Introduction
- 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.
3Why do this?
- Web service ontologies are intended to assist
with - Discovery
- Dynamic execution
- Chaining
- Automating the publish-find-bind model.
4OWL-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
5ServiceProfile
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
6GetCapabilities
- Content of GetCapabilities mapped to OWL-S.
- This process could be automated for WFS and WMS.
- Augment with semantic links.
7The 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.
8The 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.
9OWL-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.
10The 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.
11Children 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
12How 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.
13Dynamic 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.
14Whats 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(No Transcript)
16What did we find?
- Its very cumbersome.
- Full implementation of OWL-S includes IOPR more
than once (different purposes) - Difficulties with cardinality constraints.
17How 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.
18Its a limited implementation
- Didnt fully describe preconditions and results.
- Didnt fully model the complexity of some
parameters. - Process model limited.
19Conclusions
- 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.
20Questions or Comments?
- or contact me
- kristin.stock_at_nottingham.ac.uk