Geographical Service:

Gianluca Correndo, Manuel Salvadores, Yang Yang, Nicholas Gibbins, Nigel Shadbolt

A compass for the Web of Data

2

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

3

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

4

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?

5

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

6

Qualitative Spatial Relations • Region Connection Calculus (RCC8) proposed by

Randell, Cui, and Cohn – Euclidean space representation and reasoning

€

contains = TPPi ∪NTTPi

€

contained = TPP∪NTTP

7

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

8

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)

9

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

10

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

11

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

12

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)

13

Geographical service - frontend

14

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)

15

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

16