GetLOD - Linked Open Data and Spatial Data Infrastructures

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GetLOD - Linked Open Data and

Spatial Data Infrastructures

W3C Linked Open Data LOD2014 Roma, 20-21 February 2014

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Context



Geoportal & OpenData Portal



SDI management



Towards Linked Open geoData



GetLOD: Open GeoData Solution

Agenda

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Context

• Local and interoperable Geo-Information (GI) is

crucial for an increasing number of added value

services provided by private companies on top of

“open government data”

• Actually, local governments are playing an emerging

role as they represent authoritative sources for

high-quality certified data for interlinking external

information, and for smart cities applications

• In Europe main drivers for interoperable and open

data are

INSPIRE

and

Public Sector Information

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Context

• Usually geographical datasets are provided as

“quick-and-dirty”, simple and flat predefined files, with

heterogeneous data models, semantics, content, as

well

• Four critical issues:

– Local data should be published on different infrastructures; – SDI and LOD infrastructures are not interoperable;

– Two parallel workflows and risk of additional workload and data quality;

– GI lacks persistent URIs and information cannot easily be linked on record level.

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GetLOD is an open and reusable solution for publishing geographic data on the Web as Linked Open Data, according to the standard RDF / XML.

GetLOD thus ensures the Web publication of geospatial

data and its related metadata as open and linkable

data, starting from traditional cartographic webservices

GetLOD: Open GeoData Solution

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Geoportal & OpenData Portal

• The Geoportal represents an important part of the

Open Data policy of the Region Emilia-Romagna.

• With a strong integration with the regional Open

Data portal, the Geoportal is a provider of

(geo)data in favor of the portal

dati.emilia-romagna.it

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ER Geoportal

• The ER Geoportal allows the diffusion, the distribution

and the use of geospatial data, information and

geographical services both to the public and the

staff of the local and national government.

• It is compliant to the latest regional, national (AGiD)

and international (INSPIRE, CEN, ISO, OGC)

standards in terms of interoperability.

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ER Geoportal

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ER Geoportal

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ER Geoportal

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Regional SDI management

Moka is a suite to organize

the Geographic Information

System and to develop

applications that provide GIS

services to citizens,

professionals and businesses.

Regione Emilia–Romagna

organizes his SDI with

Moka Catalog and builds

GIS applications with

Moka CMS (Content

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SDI and LOD will interoperate

through Moka

In Regione Emilia – Romagna SDI and LOD infrastructures

will interoperate through Moka.

• Moka Content Management System organizes SDI

and builds GIS applications (web, desktop, apps for

smartphone).

• Moka Catalog organizes the whole SDI

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SDI and OpenData will

interoperate through Moka

How Moka (CMS GIS) helps users to create OpenData

through GetLOD

In Moka Catalog user selects the geodata to

be published as Open Data

Moka Catalog invokes GetLOD services to create Open Data Open Data are catalogued

in Moka repository

From Moka users can manage the update of Open Data

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4

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In Regione Emilia – Romagna Moka will

Catalog OpenData Oraganize SDI • GeoData • RDBMD and tables • Web services

• Metadata (RNDT, Metadata RER) • OpenData

• Functions and appications

Create applications with data and OpenData • Web Applications • Desktop Applications • Apps for smartphone

• Uses GetLOD services

Create OpenData

SDI and OpenData will

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Data, if isolated, have little value.

The value of data increases when different data sets, produced and published independently by different individuals, can be crossed freely – by third parties.

The generation of dataset in RDF format (Linked Data)

increases the value of the data allowing connections among themselves and with external dataset!

Towards Linked Open geo-Data

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Towards Linked Open geo-Data

• Free data is not enough!

In order to offer a really useful service to citizens,

institutions and companies, you need to aggregate, process data and offer them as services.

• The creation of an "ontology network" of the Geoportal data allows to move from one conceptual dataset to another.

• Ontologies are considered one of the pillars of the

Semantic Web:

a number of on-going initiatives in EU Member States and EU projects (such as InGeoCloudS, GeoKnow and SmartOpenData) are creating RDF vocabularies based on the INSPIRE data models.

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L'integrazione a livello di dati

Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito

L'integrazione a livello di dati

Applicazione sopra il modello concettuale esplicito

Integration at the level data Application over conceptual model

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The focus of GetLOD is on the governance of Linked Open Data from authoritative sources: data about

addresses and buildings derive from municipal registers

(e.g. building permits) provided by more than 200 municipalities, 9 provinces and gathered by the Region in the DBTR (Regional Topographic DB).

GetLOD: Open GeoData Solution

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Open and reusable solution

 It is integrated with the Spatial Data Infrastructure thanks to the standards defined by the Open

Geospatial Consortium (OGC) WFS and CSW.  It allows to publish the geographic open data

both as RDF (Linked Open Data ) and, as a side effect, in other non-linkable

interchange formats Shapefile and GML )

GetLOD: Open GeoData Solution

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20 GeoRepository GI Middleware MD 19115 RDF dump TripleStore www OGC server OGC WFS

GI Data & Metadata LOD Back-end MD server OGC CSW Download Triple server LOD Front-end JAVA API connettori mapping file GetLOD MD catalogo Open Data Catalogo catalogazione Ricerca API

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GetLOD is substantialy a batch RDFizer that extracts data from OGC services and transforms them in

RDF/XML.

It’s a java application that can execute scheduled transformation jobs.

A mapping file between GML elements and an ontology concepts controls the transformation.

The core transformer is based on Apache Velocity.

Data as well metadata are transformed in RDF graphs.

GetLOD: Open GeoData Solution

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GetLOD has a plug-in architecture for what concernes the output destination of data extracted, so you can: • Create a dump file;

• Transfer the file and index it on the ER custom open data portal;

• Load the data into standard (CKAN) open data portals using APIs.

• Load the data into a SPARQL endpoint • ...

GetLOD: Open GeoData Solution

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Ontologies used by GetLOD have been derived directly

from the conceptual model of the Topographic DB or, better, from the dissemination model of the DBTR.

We did not start from scratch, asking ourself “what is a building?”. In this way, the mapping of concepts was fairly direct.

Nevertheless, existing ontologies has been reused where possible, especially for geometry.

Particular attention has been paid thinking at the real use of geometry in LOD data and we made some

reasoning and drewed some conclusions…

GetLOD: Open GeoData Solution

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Geometry

1. LOD data are especially used in mash up apps that likely use common maps APIs

 WGS84 instead of official regional SRS 

GetLOD: Open GeoData Solution

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Geometry

2. If XML is verbose, RDF is really prolix

In LOD context, location usually is more important than shape

 No complex geometry, but only simple & derived 

centroids for buildings, bounding box for Administrative Units

GetLOD: Open GeoData Solution

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Geometry

3. OGC service are still there, but let’s use them only when we need them.

 Link to WFS GetFeature for Full geometry 

If an app need to draw the shape of a particular building, RDF carries the GetFeatureByID query as the value of a specific ontology predicate.

GetLOD: Open GeoData Solution

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Geometry

4. Standards are important, but does anyone already use them?

 Use “OGC GeoSparql”, but even “WGS84” 

Redundancy is not a problem in LOD

GetLOD: Open GeoData Solution

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In order to extract spatial LOD from SDI, some basic principle must be adopted in the SDI data model; fortunately DBTR already was almost compliant:

1. Unique and persistent identifier for every geographic object

2. Hystorical management and object’s life cycle well defined

But some things could be better: 1. UUID are not URI friendly

2. Codelist vs dictionaries

GetLOD: Open GeoData Solution

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Not all geographical object are noteworthy: it makes no sense to convert to LOD a contour line or a land cover

polygon.

Only spatial object that can be thought as individual that can evolve in time (change and eventually die) and can be referred by other objects in the same or other datasets can be correctly converted to LOD. A lifeless object does not really die, that’s why you

should define its life cycle, that is which are the events that terminate its individual identity.

GetLOD: Open GeoData Solution

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Interlinking

The data that GetLOD extracts do not have interlinks for the moment.

Interlinks are important but since we are talking about datasets coming from authoritative sources, interlinks

that lead to general dataset like Geonames do not add particular value.

Interlinks should be created also from other PA datasets towards these reference data.

GetLOD: Open GeoData Solution

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GetLOD: Open GeoData Solution

31 1. Identification & dataset selection 6. validation 7. release 2. cleaning up 3. analysis & modeling 4. enrichmenet 5. external linking