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Ontology Modules by Layering. Facilitating Reuse in a Geographical Semantic Web Context. Ontology and Integration. A Semantic Web lift-off requires critical mass and/via wider acceptance. Ontology development still at a stage where little interchange between organisations?

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ontology modules by layering

Ontology Modules by Layering

Facilitating Reuse in a Geographical Semantic Web Context

ontology and integration
Ontology and Integration
  • A Semantic Web lift-off requires critical mass and/via wider acceptance.
  • Ontology development still at a stage where little interchange between organisations?
  • Ontology Reuse is a key Integration benefit.
  • Merger, Alignment and Mapping complexity issues when considering Integration.
ontology and integration1
Ontology and Integration
  • Developer reluctance – easier to re-invent own dedicated local ontology specification than reuse.
  • Reuse of an external ontology will likely result in descriptive and structural irrelevances.
  • A move towards smaller component ontology modules – that can then be improvised as required – may encourage wider usage/take-up
ontology integration
Ontology Integration

Possible Ontology [ On ] Objectives

  • Merger: OA + OB→ OC
  • Alignment: OA≡ OB≡ OC
  • Mapping: a virtual integration where OA, OB and OC concepts are semantically related.

Methods

  • 1 and 2 are achieved by rewriting (reformulation).
  • Original ontologies are subsumed or made consistent (respectively).
  • 3 is achieved by mappings between concepts of imported ontologies. A, B and C endure autonomously.
  • Ontology Reuse, in this presentation, refers to 3: Mapping.
informal specific class reuse
“Informal” specific Class Reuse
  • Using namespace declaration to explicitly specify a single external concept, e.g.

<rdf:RDF xmlns="http://www.livewiredg.myby.co.uk/rdf/geo-layers/rail.owl#"

xmlns:cyc="http://www.cyc.com/2003/04/01/cyc#" >

<owl:Class rdf:about="&cyc;TransportationCompany"/>

<owl:Class rdf:ID="RailOperator">

<rdfs:subClassOf rdf:resource="#RailwayComponent"/>

<rdfs:subClassOf rdf:resource="&cyc;TransportationCompany"/>

</owl:Class> ……..

  • Is this acceptable? How would an agent understand the Cyc context of the superclass of “cyc:TransportationCompany”
formalised specific class reuse
“Formalised” specific Class Reuse

E-Connections

  • Representation and reasoning with foreign ontologies (Grau et al, 2005)
  • Allows specific concept linking. Few tools available e.g. SWOOP (OWL Ontology Editor)

<rdf:RDF

xmlns:global="http://www.livewiredg.myby.co.uk/rdf/geo-layers/global.owl#"

xmlns=http://www.owl-ontologies.com/flight.owl# ……..>

<owl:Class rdf:about=“&global;Artifact"/>

<owl:Class rdf:ID="Helicopter">

<rdfs:subClassOf>

<owl:Restriction>

<owl:onProperty>

<owl:LinkProperty rdf:about="#hasForm"/>

</owl:onProperty>

<owl:someValuesFrom rdf:resource="&global;Artifact"/>

</owl:Restriction>

</rdfs:subClassOf>

</owl:Class>

<owl:LinkProperty rdf:ID="hasForm">

<owl:foreignOntology rdf:resource="&global;"/>

<rdfs:domain rdf:resource="#Helicopter"/>

<rdfs:range>

<owl:foreignClass rdf:about="&global;Artifact">

<owl:foreignOntology rdf:resource="&global; "/>

</owl:foreignClass>

</rdfs:range>

</owl:LinkProperty>

formalised specific class reuse1
“Formalised” specific Class Reuse
  • SWOOP permits ontology partitioning (module extraction)
  • partitioning generates same syntax as “informal reuse” example
class reuse by ontology import
Class reuse by Ontology Import

Objective:

Map Rail Ontology class “RailOperator” to Cyc Ontology class “TransportationCompany”

Action:

Import Opencyc into Rail > 6.8MB

Effect:

adds 2843 classes

1256 properties

6331 instances

Protégé “out of memory”

load time 1.5 to 7.5 mins

alternative reuse approach
Alternative Reuse approach?
  • Consider the way Ontologies structured?
  • Break down domain ontologies into sub-components: effectively domain “sub-classes” (Layers / modules)
  • How to demonstrate?
  • Can be demonstrated using Geographical context
why consider geography context
Why consider Geography Context?
  • Geographical concepts interact with virtually every aspect of daily life.
  • Geographical elements form a major part of information management systems.
  • Geographical ontologies offer a logical vehicle, to examine how Web semantics can be specified efficiently and effectively.
pc and ontology analogy
PC and Ontology Analogy
  • Adding a component to a PC
    • To enhance our own PC, we would not buy a complete PC with all components specified,
    • It would require dismantling and refitting – some parts may not be compatible
    • Result: additional, unnecessary and costly extra work.
  • Accepted Protocol
    • Build our requirement from small, interchangeable components
    • Preferably with multiple PC compatibility.
ontological comparison
Ontological Comparison
  • Multiple sub-domains
    • potential redundancy
    • vulnerability to change
  • How relevant are they?
  • Ontology Reuse - Imports
    • should there be a similar approach?
    • E.g. if OTN 1 is imported: what do we see?
    • Ontology much smaller than Cyc, but …
  • Only for an application that uses ALL concepts

1OTN - Ontology of Transportation Networks (Lorenz et al, 2005)

transport ontology
Transport Ontology
  • How might we approach developing a modular ontology set?
  • Previously discussed considering “map layers”
  • No scientific justification for this - but offers a conceptual discipline that could be exploited for our purposes
  • Example: consider a “LandTransport” ontology …..
developing layers
Developing Layers
  • Need to “de-integrate” to allow low-cost integration
  • We are aiming towards “effectively” disjoint domains
  • Achieved by removing concept redundancy – potential duplication
  • Need to promote/relegate concepts and relations
  • Represents a separation of Form and Function both within and between ontology modules
  • e.g. see …… TransportInterchange, LevelCrossing
rail transport ontology

Road domain

Rail Transport Ontology

Q: rename LevelCrossing → RoadCrossing?

But we don’t do roads in rail!

road transport ontology

Rail domain

Road Transport Ontology

Q: rename LevelCrossing → RailCrossing?

But we don’t do rail in roads!

road rail ontology multimodal

ChannelTunnel Terminal

DriveOn-DriveOffRole

LevelCrossing

TransportInterchange

Road-Rail Ontology: Multimodal
benefits and issues
Benefits and Issues
  • Advantages
    • Small is manageable
    • Select only required building block modules
    • Independent therefore less vulnerable to change
    • Change is isolated to the module and subsuming domain?
  • Disadvantages
    • Increased mappings?
    • Needs to be examined
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