Ontology modules by layering
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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

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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?

  • Ontology Reuse is a key Integration benefit.

  • Merger, Alignment and Mapping complexity issues when considering Integration.

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

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.


  • 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

  • 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


  • Representation and reasoning with foreign ontologies (Grau et al, 2005)

  • Allows specific concept linking. Few tools available e.g. SWOOP (OWL Ontology Editor)



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

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

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




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


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




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

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

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


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

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




“Formalised” specific Class Reuse

  • SWOOP permits ontology partitioning (module extraction)

  • partitioning generates same syntax as “informal reuse” example

Class reuse by Ontology Import


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


Import Opencyc into Rail > 6.8MB


adds 2843 classes

1256 properties

6331 instances

Protégé “out of memory”

load time 1.5 to 7.5 mins

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?

  • 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

  • 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

  • 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)

Fixed Concepts

Variable Concepts

Ontology Permanence

Fixed Classes

Variable Classes

Ontology Permanence

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 …..


single-mode ?

Land Transport

Road-Rail Interchange




Our Transportation Domain




Transportation Domain Layers

Railway sub-domain Conceptualisation

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

Road domain

Rail Transport Ontology

Q: rename LevelCrossing → RoadCrossing?

But we don’t do roads in rail!

Rail domain

Road Transport Ontology

Q: rename LevelCrossing → RailCrossing?

But we don’t do rail in roads!

ChannelTunnel Terminal




Road-Rail Ontology: Multimodal

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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