geographical service: gianluca correndo, manuel salvadores, yang yang, nicholas gibbins, nigel...
Post on 19-Dec-2015
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Geographical Service:
Gianluca Correndo, Manuel Salvadores, Yang Yang, Nicholas Gibbins, Nigel Shadbolt
A compass for the Web of Data
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Outline• Introduction
– Public Sector Information– Ordnance Survey– Qualitative Spatial Relations
• Geographical Service for GB
– SCOVO data alignment– Geographical Service (RESTful API & frontend)– Backlinking service
• Future Work
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Public Sector Information• UK Government committed to free public sector
information
– Usually Excel or CSV to RDFize (http://data.gov.uk)
– Linked Data already published (e.g. OS, Openly Local, education, and statistics?)
– More to come
• High volumes of data
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Public Sector Information• EnAKTing project investigating how to integrate it,
query it, manage it
• PSI data sets usually describe the territory and its resources
– Geographical information is therefore a key aspect of its classification
– How to describe data about territory, and how to exploit it?
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Ordnance Survey• Great Britain’s mapping agency
• Released an Administrative KB of Great Britain in Linked Data format
– From European Region (e.g. South-West England) to single parishes and constituencies
– Region connection relations are also described
• There is a concrete opportunity of exploiting authoritative knowledge for providing a geographical context to the other information
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Qualitative Spatial Relations • Region Connection Calculus (RCC8) proposed by
Randell, Cui, and Cohn
– Euclidean space representation and reasoning
€
contains = TPPi ∪NTTPi
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contained = TPP∪NTTP
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Geographical Service for GB• All PSI data sets published so far has one
geographical dimension:
– Different granularity used (from constituency to European region)
• Need to align the geographical entities to an authoritative kb
– Once aligned need to exploit such a reference – Qualitative Spatial Relations can be used then to
retrieve related entities (e.g. all sub-regions of a region)
– Need to retrieve back links from reference URIs
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Rationale for a Geographic service• Use of URIs alone for
providing context to resources is not always enough
• A semantic gap can be easily covered exploiting existing knowledge about the domain (in this case about GB geography)
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SCOVO Data Alignment• Every SCOVO data set is a collection of SCOVO
Items
• Every SCOVO Item is a value plus a number of dimensions that put the value into context
• Geographical dimensions have been represented as URIs and aligned towards the OS Administrative ontology
• Geographical service + Backlinking service retrieve the items relevant for a given region
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Geographical service – the data• OS Administrative
ontology
• Co-reference service for both inward URI normalization and outward result translation
• New knowledge (relations between entities) is created in the process
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Geographical service – the API• http://geoservice.psi.enakting.org/{command}/
{dictionary}/{format}/{URI}
– command = contains or container
– dictionary = one of {dbpedia, os, geonames, statistics, geonames, enakting, opencyc, openlylocal, none}
– format = rdf or text or ttl or json
– URI = input URI of the entity to make the containment closure
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Geographical service – the API• The service takes the input URI and find via co-
reference system the equivalent URI in OS KB
• The contained/container entities are retrieved via SPARQL (forward chaining reasoning upon the OS KB)
• The resulting OS URIs are translated in the target dataset (e.g. dbpedia, enakting, etc.) via co-reference system
• The URIs are then serialized in the chosen format (i.e. text, rdf/xml, rdf/turtle, or json)
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Back-linking support• Once relevant URIs have been retrieved, a further
step is usually requested
• Relevant URIs are in fact usually used to provide context to other information, it’s that information we’re aiming at
– The backlinks issue is long known from hypertext literature
– Linked data world is built on top of an hypertext framework (the Web)
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Back-linking support• The adoption of hub ontologies/KBs stresses the
problem of handling such backward references
– Resolving authoritative URIs in fact does not return all the entities that used that URIs
• Application indexing services can be built for retrieving such back links exploiting therefore authoritative sources of URIs