The importance of persistent URIs for the

implementation of INSPIRE

INSPIRE Conference 2012, Istanbul

Clemens Portele, interactive instruments GmbH

Drafting Team Data Specifications (Chair)

Directive, Article 8(2)(a)

"The implementing rules shall address a common

framework for the unique identification of spatial

objects, to which identifiers under national systems can

be mapped"

Main purpose of identifiers in INSPIRE

• Unambiguously trace spatial objects / support managing

lifecycles of spatial objects including versioning

• Support reuse by providing access to these objects via an

identifier, e.g. for linking spatial data with other information

Note: Spatial data sets are spatial objects, too

Types of identifiers in spatial data sets

Types of identifiers in spatial data sets

Types of identifiers in spatial data sets

identifierlinguistically independent sequence of characters capable of uniquely and permanently identifying that with which it is

associated

object identifieridentifier

associated with a spatial object

thematic identifier

identifier used to identify a real-

world phenomenon

registered item identifieridentifier of a resource

maintained in a register

geographic identifier

spatial reference in the form of a label or code that identifies a location

Directive, Article 11(1)

"Network services shall be accessible via the Internet

or any other appropriate means of telecommunication"

� Identifiers in the regulation have been defined independent of

the network service platform as

a namespace and

a local identifier in the namespace

From regulation to implementation

• The world has moved on since the Directive was written

• Today, the only reasonable assumption is that INSPIRE will be

implemented as part of the web

• We need to adopt standard web practices in the

implementation of INSPIRE – or fail

• This has far-reaching implications for the implementation, in

this presentation the focus is only on identifiers

The web and identifiers

• In the web, http URIs have become the primary way to

reference information resources

• These http URIs must be stable

• There is an expectation that using the URI information about

the identified resource can be retrieved using HTTP

Implications

• Need to map all identifiers in INSPIRE to http URIs

• URIs must be independent of implementation details and

should be short and mnemonic

• Member States, the Commission and other organisations

assigning identifiers need to develop URI schemes to manage

assignment of http URIs

• Typically this should be done with a wider scope than just

spatial data

• Infrastructure needs to be set up and maintained to resolve

http URIs and return information resources

INSPIRE

<cp:CadastralParcel

gml:id="DERPAL00ah5ztj3js2">

<gml:identifier>

http://location.example.de/so/

AAA/DERPAL00ah5ztj3js2

</gml:identifier>

<cp:areaValue uom="m2">

673.5

</cp:areaValue>

<cp:label>255/1</cp:label>

<cp:nationalCadastralReference>

07012302802550001

</cp:nationalCadastralReference>

<cp:geometry>

<gml:Polygon>... </gml:Polygon>

</cp:geometry>

...

</cp:CadastralParcel>

CadastralParcel

geometry

cadastral

reference

07012302802550001

identifier http://location.example.de/so/AAA/D

ERPAL00ah5ztj3js2

area value 673.5 m2

...

Cadastral Parcel

http://kataster.example.de/id/parcel/07

/123/28/255-1

Real World Spatial Object Representation (GML)

http://xyz.de/doc/parcels?

...&ID=DERPAL00ah5ztj3js2

(Request to a Download Service)

Abstraction

255/1

Description

Illustration

Object identifiers as http URIs

� The URI of the spatial object

http://location.example.de/so/AAA/DERPAL00ah5ztj3js2

� follows a simple pattern in this example:

http://location.example.de/so/{namespace}/{localid}

� Retrieving this URI would redirect – using standard HTTP – to a

download service that provides representations of the spatial

object, e.g. in GML, JSON, HTML, RDF, etc.

� The identifier of the spatial object is stable and not affected by

changes in the implementation / download services

� References to the spatial object have to use the stable http URI,

not the URI provided by the download service

An example from the UK

� Pattern used by the UK:

http://{subdomain}.{domain}/{type}/{metadata}/{authority}/{id}/{version}

� A Bathing Water Quality Monitoring Sampling Point:

http://location.data.gov.uk/so/ef/SamplingPoint/bwsp.eaew/36800

Remarks:

• {metadata}: UK has included the INSPIRE theme and spatial object type in the

URI. Potentially this will help users/applications. The entries are derived from

INSPIRE code lists.

• {type}: "id" = real world phenomenon. "so" = spatial object. "doc" = web document

in HTML, RDF, JSON, GML, etc. "def" = definition, e.g. an item in a code list

• Retrieving the "so" URI above redirects using standard HTTP mechanisms to a

"doc" URI that in turn provides representations of the spatial object

An example from the UK

Identifiers of other shared resources

• Spatial objects reference a number of other resources that

are maintained in registers and used consistently

• These resources are identified by URIs, too

• Example: The coordinate reference system of a geometry

http://www.opengis.net/def/crs/EPSG/0/4258

• Example: A code list value

http://inspire.ec.europa.eu/codelist/countrycode/de

Note: The code list URI does not yet return anything, but will once the INSPIRE code list registry

has been set up

Why make spatial objects available on the web and

not just spatial data sets?

• To enable and encourage linking between spatial objects in

different data sets (marker post along road link, sensor attached to

mast, etc.)

• To provide location context to "business information" in a way that

can be used in web/mobile applications (property rights associated

with a parcel, timetable of a railway station, statistical information

for a statistical unit, materials used at an industrial facility, etc.)

• To support the implementation of the Digital Agenda for Europe and

the European Interoperability Framework

• Like all of INSPIRE, this can only be successful, if access to

spatial data is not encumbered by restrictions that result in a

lack of reuse of the spatial data

Additional information

INSPIRE Generic Conceptual Model (INSPIRE)

http://inspire.ec.europa.eu/index.cfm/pageid/2

Guidelines for the Encoding of Spatial Data (INSPIRE)

http://inspire.ec.europa.eu/index.cfm/pageid/2

Designing URI Sets for Location (UK)

http://location.defra.gov.uk/wp-content/uploads/2011/09/Designing_URI_Sets_for_Location-V1.0.pdf

Designing URI Sets for the UK Public Sector (UK)

http://www.cabinetoffice.gov.uk/resource-library/designing-uri-sets-uk-public-sector

Cool URIs for the Semantic Web (W3C)

http://www.w3.org/TR/cooluris

This paper not only applies to RDF, but also other representations of resources