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Claus Stadler, Sören Auer AKSW Research Group University of Leipzig - Talk at "Vienna Semantic Web Meetup" in Graz on Sept 6, 2011
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Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 1
Linked (Geo) DataAdding a Spatial Dimension to the Web of Data
Claus Stadler, Sören Auer AKSW Research Group University of Leipzig
http://linkedgeodata.org
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 2
Structure
● Linked Data● LinkedGeoData
● Architecture● Mapping to RDF/OWL● Interlinking● Applications● Issues & Future work
● Open Governmental Geo Data
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 3
The emerging Web of Linked Data
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 4
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 5
LinkedGeoData
Conversion, interlinking and publishing of OpenStreetMap.org data sets as RDF.
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 6
Motivation
● Ease information integration tasks that require spatial knowledge, such as
● Offerings of bakeries next door● Cinemas nearby and their programs● Historical sights along a bicycle track
● Therefore use RDF/OWL in order overcome structural and semantic heterogeneity.
● LOD cloud contains data sets with spatial features● e.g. GeoNames, DBpedia, US census, EuroStat● But: they are restricted to popular or large entities like countries, famous
places etc.● OSM offers buildings, roads, mailboxes, trash bins/recyling, ...
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 7
What do we offer?
● Very large RDF knowledge base derived from OpenStreetMap
● REST API, static & live SPARQL endpoints
● Update propagation of the added and removed triples
● 845.000 Interlinks with DBpedia, GeoNames, and FAO
● LGD-Browser
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 8
Architecture
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 9
OpenStreetMap - Datamodel
● Basic entities are:● Nodes Latitude, Longitude
● Ways Sequence of nodes
● Relations Associations between any number of nodes, ways and relations.
● Each entity may be described with tags:
key-value pairs, such as (amenity, school)
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 10
Example: Leipzig's Zoo
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 11
OSM entities → RDF
● Three types of mappings based on (osm-id, key, value)
● Text– (5, name, Leipzig) → lgd:node5 rdfs:label ”Leipzig”
– (5, name:de, Leipzig) → lgd:node5 rdfs:label ”Leipzig”@de
● Datatype properties– (6, seats, 4) → lgd:node6 lgdo:seats ”4”^^xsd:integer
● Classes/object properties– (7, amenity, school) → lgd:node7 a lgdo:School
– (8, amenity, rare value) → lgd:node8 a Amenity
– (9, religion, hindi) → lgd:node9 lgdo:religion lgdo:Hindi
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 12
Ontology
● Text, class, and object property mappings manually crafted
● Subclass relations inferred from class-mappings:(..., amenity, school) → ... a School
(..., amenity, rare value) → ... a Amenity
School subClassOf Amenity
● Automatically mapped OSM keys with mostly numerical values to datatype properties● boolean, integer, float
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 13
Ontology
● Enriched classes and properties with multilingual labels from TranslateWiki● http://translatewiki.net
● Imported icons for 90 classes from the freely available icon collection from the SJJB Management● http://www.sjjb.co.uk/mapicons/
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 14
Ontology
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 15
Instance Data
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 16
Statistics (2011-Feb-23)
● 222.539.712 Triples● 6.666.865 Ways● 5.882.306 Nodes
● Among them● 352.673 PlaceOfWorship● 60.573 RailwayStation● 59.468 Recycling● 50.955 Town● 30.099 Toilet● 7.222 City
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 17
DBpedia Mapping
Given a point from DBpedia, GeoNames, …, query LGD points with certain types within a maximum distance
Basic idea (performed with Silk):
● Find most similar type(s) in LGD for a type in another knowledge base
● Compute spatial score
● Compute name similarity (rdfs:label)
● Combine both scores
● Depending on final score, either automatically accept/reject links or mark for manual verification.
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 18
How to access the data?
● Rest Interface (based on Postgis DB, full osm dataset loaded, > 1billion triples)
● Supports limited queries (e.g. circular/rectangular area, filtering by labels)
● Sparql Endpoints (based on Virtuoso DB, subset of osm dataset loaded, ~222mio triples)
● Static (http://linkedgeodata.org/sparql)
● Live (http://live.linkedgeodata.org/sparql)
● Downloads (same data as in the SPARQL endpoints, http://downloads.linkedgeodata.org)
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 19
Applications: LinkedGeoData Browser
http://browser.linkedgeodata.org
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 20
Applications: Generic spatial data browsing widgets
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 21
Applications: MovieGoer
● MovieGoer– Scrapes websites with information
about the programs of cinemas in Innsbruck and Munich
– Interlinked with LinkedGeoData in order to obtain address information
– During development: missing cinemas added to OSM; became available for interlinking through LGD-Live.
http://lokino.sti2.at/
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 22
More Applications
● Layar
Augmented reality browser for mobile phones, features a LGD layer
http://layar.com
● Vicibit
Generates embeddable HTML code for displaying a map of POIs of certain types in a specified area
http://vicibit.linkedgeodata.org
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 23
Issues & Future work
● Converting all OSM data to RDF not feasible:
> 1.000.000.000 nodes
→ only a subset of OSM's data available via the SPARQL endpoints
● Virtuoso only supports point geometries
● Possible solution: Rewriting SPARQL queries to the OSM SQL schema● Work in progress, no estimate on a release yet
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 24
Issues and Future Work
● Investigating further applications of LGD, such as using the LGD knowlegde base for named entity recognition/resolution
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 25
Open Governmental Geo Data
● Most governmental data has a spatial dimension● transportation, statistics, finances, etc.
● Geo Data is a driver in the Open Government Data realm● ordenance survey, geodata.gov.gr, …
● It is still difficult to extract, publish, interlink, author and visualize Governmental Linked Geo Data● LOD2 Stack (ckan integration, browsing widgets,
integrated comprehensive tool compilation)
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 26
Best practices
● Reuse of vocabularies
● vCard: address information, phone & fax
● Good Relations: Opening hours, product descriptions
● GeoOWL: latitude, longitude, polygons
– GeoSPARQL Ontology● Foaf: based_near
● Dublin core (dc): Document meta data
● …
http://www.leipzig.de/de/buerger/jugend/betreuung/kitas/
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 27
Transportation
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 28
Comprehensive Knowledge Archive Network (CKAN)
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 29
Financial Transparency
Universität Leipzig ▪ Agile Knowledge Engineering and Semantic Web (AKSW) Authors: Sören Auer, Jens Lehmann, Claus Stadler Slide 30
The End
Thanks for your Attention!