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Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds...

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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
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Page 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.

Describing OGC WMS and WFS with the OWL-S Web

Service Ontology

Dr Kristin Stock

Allworlds Geothinking, UKCentre for Geospatial Science, University of Nottingham, UK

EDINA, UK

Page 2: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

Page 3: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

Why do this?

• Web service ontologies are intended to assist with:– Discovery– Dynamic execution– Chaining

• Automating the publish-find-bind model.

Page 4: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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

Page 5: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

ServiceServiceGrounding

ServiceProfile

ServiceModel

presents(what it does)

supports(how to access it)

describedBy(how it works)

Domain Ontology (Feature Types)

Inputs, Outputs,Preconditions and Results

Inputs, Outputs,Preconditions and Results

Page 6: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

GetCapabilities

• Content of GetCapabilities mapped to OWL-S.

• This process could be automated for WFS and WMS.

• Augment with semantic links.

Page 7: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

Page 8: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

The OWL-S OGC Ontology (2)

• For WFS and WMS, the OWL-S OGC Ontology is quite comprehensive, because specs are specific – wouldn’t be so for WPS.

Page 9: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

OWL-S OGC Ontology: What’s 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.

Page 10: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

The Grounding• OWL-S has a WSDL

grounding.• We didn’t use it because

it’s XML, not OWL – doesn’t fit our architecture.

• Could have applied the WSDL – RDF mapping but time limited.

• Created a new grounding.

Page 11: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

OGCHttpGrounding

OGCHttpOperation

OGCHttpParameter

Domain QueryModel

OGCHttpConstraint

hasOGCHttpOperation

hasOGCHttpParameter

hasOGCHttpConstraint

hasDomainhasQueryModelhasDomain

CheckBox

InputBox OptionList

RadioButton

isA

Process:Parameter

groundsAbstractParameter

Children of Process:AtomicProces

s(for each WFS and WMS operation)

groundsAtomicProcess

has<OperationName>Inputhas<OperationName>Output

Meaning

PossibleValues DefaultValu

e

DataType

DomainMetadata

ValuesUnit

hasComponent

Page 12: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

Page 13: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

Page 14: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

What’s 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 don’t have to repeat IOPR.

Page 15: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.
Page 16: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

What did we find?

• It’s very cumbersome.• Full implementation of OWL-S

includes IOPR more than once (different purposes);

• Difficulties with cardinality constraints.

Page 17: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

Page 18: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

It’s a limited implementation

• Didn’t fully describe preconditions and results.

• Didn’t fully model the complexity of some parameters.

• Process model limited.

Page 19: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

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.

• Didn’t test orchestration.

Page 20: Describing OGC WMS and WFS with the OWL-S Web Service Ontology Dr Kristin Stock Allworlds Geothinking, UK Centre for Geospatial Science, University of.

Questions or Comments?

or contact me:[email protected].

uk


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