INTEGRATING AUTHORITATIVE AND VOLUNTEERED GEOGRAPHIC INFORMATION -

AN ONTOLOGICAL APPROACH

Crowd Sourcing in National Mapping Internship Funding

ACTIVITY Workshop

Leuven (Belgium)14th May 2013Jimena Martínez Ramos [jmr125@mun.ca]

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Table of contents

1. Background

2. Problem

3. Objective

4. Proposed approach

5. Semantics in OSM datasets (ongoing work)

6. Conclusions and future work

Background

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(*) http://ggim.un.org/ (UN Report, 2012)

National Mapping Agencies (NMAs) are likely to find difficult to justify the costs of traditional data maintenance mechanisms.

VGI projects (like OpenStreetMap) are growing and are seen as a good data source to be integrated with authoritative datasets.

There is growing need of integrating different data sources.

Semantic interoperability is still an issue in the integration problem.

The need of integrating Geographic Information from different sources

?

Levels of heterogeneity

System

Syntactic

Structural

Semantic (meaning of words)

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The ProblemSemantic Heterogeneity in Geographic Information

motorway

Conceptualization

turnpike

trunk

Conceptualization Words or symbols stand for things through ideas

Different conceptualizations:

Semantic Heterogeneities

Ogden and Richards, 1923

ConceptualizationConceptualization

Reality (road)Symbol (freeway)

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trunk

Conceptualization

The ProblemSemantic Heterogeneity in Geographic Information

turnpike

Pre-processEverybody thinking the same

Post-processMatching symbols with the same meaning

STANDARDS!ONTOLOGIES!

Reality (road)

Conceptualization

freewayfreeway

Conceptualization

Conceptualization

trunkConceptualization

ConceptualizationConceptualization

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ObjectSubject

RoadTransportation

“Explicit specification of a conceptualization” Gruber, 1993

They are ways to conceptualize a domain.

The ProblemWhat are ontologies about?

Class Properties (Sub)class

isSubclassOf

Predicate

isSuperclassOf

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Ontology3

Dataset 2turnpike

Dataset 1Freeway

Ontology2

Ontology1

?

ObjectiveUsual approach to geodata integration using ontologies

Turnpike =

motorway

Freeway=

motorway

Freeway+ Turnpike

= motorway

Freeway+ Turnpike

motorwayCommon Standard

conceptualization

Interoperable datasets

Ontology and Standard approach to semantic integration

VGI(OSM)motorway

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motorwaytrunk

freeway

Official source 1

turnpike

Proposed ApproachThe method according the objectives

“turnpike”

“freeway”

#user 1: “trunk”

#user n: “motorway”

R2RMLmapping

R2RMLmapping

“motorway”

“moto

rway”

R2RMLmapping

RDF

RDF

RDF

StandardDomain

Ontology

RealityCommon

Knowledge

“motorway”

Official source 1

OpenStreetMap

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Quebec • <highway=bus_stop>

St. John´s

▪ <public_transport=stop_position>

More than one tag per real-world phenomenon (synonymy)

Ongoing work: Semantic Heterogeneity in OSM datasets

▪▪▪

▪▪▪

▪▪

Number of tags per phenomenon increases with the scale, and % is important

• <highway=bus_stop> ▪ <public_transport=stop_position>

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More than one tag per real-world phenomenon (synonymy)

Ongoing work: Semantic Heterogeneity in OSM datasets

Number of tags per phenomenon evolve with time, and % is still important

• <highway=bus_stop> ▪ <public_transport=stop_position>

2006

2008

Agreement through timeIncreasing level of agreementDecreasing level of agreement

Conclusions and future work

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Proposed approach is based in a domain ontology, which allows:

• Matching datasets to a common pivot (R2RML allows flexible and direct mappings)

• No need to know how to handle ontologies.• Reusing the mappings.

Semantic Heterogeneity in OSM datasets.

• Number of tags and their % of occurrence per real-world phenomenon• Time and spatial scale are factors affecting SH in OSM datasets.

Future work:

• Developing more the ontology.• User-friendly interface for making R2RML mappings.• Deeper study factors involved in SH in OSM datasets, trying to model it.

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Thank you. Gracias.Questions? AGILE/EuroSDR

NSERC

TU Delft

IGN Spain

Sinfogeo Ltd.

Dr. Jean BrodeurDrs. Marian de VriesMarine and Geomatics Lab colleagues

<amenity=plane>

Acknowledgements

PNOA aerial images. IGN Spain Icons by http://dryicons.com Jimena Martinez [jmr125@mun.ca]