INTEGRATING AUTHORITATIVE AND VOLUNTEERED GEOGRAPHIC INFORMATION - AN ONTOLOGICAL APPROACH Crowd Sourcing in National Mapping Internship Funding ACTIVITY Workshop Leuven (Belgium) 14th May 2013 Jimena Martínez Ramos

Table of contents 2 1. Background2. Problem3. Objective4. Proposed approach5. Semantics in OSM datasets (ongoing work)6. Conclusions and future work

Background 3 (*) (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 SystemSyntacticStructural Semantic (meaning of words)

The Problem 4 Semantic 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 Conceptualization Reality (road) Symbol (freeway) road

trunk Conceptualization The Problem 5 Semantic Heterogeneity in Geographic Information turnpike Pre-process Everybody thinking the same Post-process Matching symbols with the same meaning STANDARDS! ONTOLOGIES! Reality (road) Conceptualization freeway Conceptualization trunk Conceptualization

6 ObjectSubject Road Transpor tation “Explicit specification of a conceptualization” Gruber, 1993 They are ways to conceptualize a domain. The Problem What are ontologies about? ClassProperties(Sub)class isSubclassOf Predicate isSuperclassOf

Ontology 3 7 Dataset 2 turnpike Dataset 1 Freeway Ontology 2 Ontology 1 Objective Usual approach to geodata integration using ontologies Turnpike = motorway Freeway = motorway Freeway+ Turnpike = motorway Freeway+ Turnpike motorway Common Standard conceptuali zation Interoperable datasets Ontology and Standard approach to semantic integration VGI(OSM) motorway

trunk freeway Official source 1 turnpike Proposed Approach 8 The method according the objectives “turnpike” R2RML mapping R2RML mapping R2RML mapping RDF Standard Domain Ontology Reality Common Knowledge “motorway” Official source 1 OpenStreetMap

Quebec St. John´s ▪ 9 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 ▪

10 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 ▪ Agreement through timeIncreasing level of agreementDecreasing level of agreement

Conclusions and future work 11 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.

Thank you. Gracias. Questions? 12 AGILE/EuroSDR NSERC TU Delft IGN Spain Sinfogeo Ltd. Dr. Jean Brodeur Drs. Marian de Vries Marine and Geomatics Lab colleagues Acknowledgements PNOA aerial images. IGN Spain Icons by Jimena Martinez