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

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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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Geographical service - frontend

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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

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