(Geospatial Semantics – Week 8)
Institute for Geoinformatics,
University of Muenster.University of Muenster.
Introduce the principles and key features of Linked
Describes the procedures to publish LD.
Provides examples of existing datasets, tools available for
publishing and using LD.
Introduces the Linked Geo-Data, Linked Geo-Sensor data.
The Web of Documents
– Documents are linked, but links are not qualified, q
– Challenges : Querying across different sources; Information
integration & discovery
Linked Data: The Web of data
Goal : to share ‘data’ rather than ‘documents’
LD Browsers, Mashups,
Goal : to share data rather than documents
Thing Thing Thing Thing
RDF D t M d l
Thing Thing Thing Thing
RDF Data Model
t d li k
Data in various
typed linkstyped linkstyped linkstyped links
The four rules…
– Use URIs as names for things (anything not just documents)– Use URIs as names for things (anything, not just documents)
– Use HTTP URIs so that people can look up those names.
– When someone looks up a URI, provide useful information, using the
standards (e g RDF SPARQL)standards (e.g., RDF, SPARQL)
– Include RDF links to other URIs to enable the discovery of related
Linked data is a style of publishing and interlinking
structured data on the Web that :
– Promotes reuse and reduces redundancy
– Ease of discovery
Ease of consumption due to standards based data sharing– Ease of consumption due to standards-based data sharing
– Added value : build ecosystems around your data/content
Linked data simplifies much of the complexity of the
Community effort to publish existing datasets as Linked
Data on the WebData on the Web
Interlink things between different data sources
Develop clients that consume Linked Data from the Webp
Is it used somewhere as well? Ja!
More datasets available at http://linkeddata.org/data‐sets
LOD on the Web Visualization : http://www.webknox.com/blog/2010/05/linked‐
Class relations amongst datasets
1. Triplification : convert existing data into RDF triples
2. Identify co-referring entities into the RDF dataset
3. Linked to the Web of Linked Data3. Linked to the Web of Linked Data
“Muenster Semantic Interoperability Lab MUSIL ”
l A foaf:topic interestowl:sameAs
t /k/K h W ht l h //db di / /S i S W b
PREFIX foaf: http://xmlns.com/foaf/0.1/
PREFIX dc: http://purl.org/dc/elements/1.1/
http://ifgi‐muenster.de/kuhn foaf:made ?paper
?paper a foaf:Document .
?paper dc:creator http://dblp.l3s.de/d2r/resource/authors/Werner_Kuhn
Linked Data Browsers, Mashups and other Client
Linked Data Publishing Platforms/Frameworks D2R Server,
Pubby, Paget, Talis Platform, etc.
Linked Data/RDF Editors and ValidatorsLinked Data/RDF Editors and Validators Hyena, Vapour
Semantic Web Search Engines
http://esw w3 org/TaskForces/CommunityProjects/LinkingOpenData/Semantichttp://esw.w3.org/TaskForces/CommunityProjects/LinkingOpenData/Semantic
Semantic Tagging and Rating
16Reference : Hausenblas M (2009), Linked Data Applications
User Interfaces and Interaction Paradigms
– Navigation controls in a LD browserg
– Scalability problems with on-the-fly link traversal and federated
Schema Mapping and Data Fusion
– Resolving semantic conflicts (e.g., mix terminology from different
– Dead links, informing link sources about changes via subscription
21Reference: Bizer C (2009), Linked Data – The Story So Far
Licensing : Data reused and republished
Trust, Quality and RelevanceTrust, Quality and Relevance
– Data relevant or appropriate to the user’s need
– Integrated view of data provenance and trustworthiness
– Higher awareness of the users about the data
– Information accountability
22Reference: Bizer C (2009), Linked Data – The Story So Far
Adds spatial and temporal dimensions to the Web of Data.
Links: geospatial web resourcesLinks: geospatial web resources
unstructured /informal GI in
structured geo-databases scientific materials
structured geo databases
(Different forms of Geographic Information on the Web)
24* Vilches-Blázquez LM, et al. (2010), An Approach to Publish Spatial Data on the Web: The GeoLinked Data Case
Entity URIs are dereferenced via LD principles
25* Lopez-Pellicer (2010), Geo Linked Data
The content negotiation model of Linked Data is extended
with support to Geoweb MIME-types.pp yp
26* Reference: Lopez-Pellicer J, et al. (2010), Geo Linked Data
– A geographical names database in RDF form.g g p
– Contains location information which is interlinked with Geonames,
the US Census Euro Stat and the CIA world fact bookthe US Census, Euro Stat and the CIA world fact book.
– Data extracted from the Open Street Map project was linked to
DBPedia instances using the links created by the users.
– OS BoundaryLine product that contains all administrative areas plus– OS BoundaryLine product that contains all administrative areas plus
Why Linked Sensor Data?
– Increase the accessibility of non-OGC data sourcesy
29Reference : Kessler & Janowicz, (2010), Linking Sensor Data – Why, to What, and How?
Inclusion of spatial operators in the current Linked Data model
to support complex queries.pp p q
Transformation from geometries to an RDF-based
representation adds complexity.
N dl d d d t d t– Needless and redundant data
‘Browse’ pattern allows the discovery by subsequent links;
‘Query’ pattern is user specified [Schade & Lutz, 2010]Q y p p [ , ]
How both approaches can be combined?
Quality of links
Undefined vocabulary terms, mismatched semantics, etc.
30Reference : Kessler & Janowicz, (2010), Linking Sensor Data – Why, to What, and How?