GetLOD - Linked Open Data and Spatial Data Infrastructures

Marco Fago

pkm026-562-1.0

Conferenza OpenGeoData Italia 2014Roma, 27 Febbraio 2014

CC-BY 3.0

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 Directives and Open Data strategies, at various levels.

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.

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

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.

ER Geoportal

Home Page of the ER Geoportal

ER Geoportal

The data catalog

ER Geoportal

Example of ISO Metadata

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 Management System).

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

• Moka builds open data using “GetLOD” services.

SDI and OpenData will interoperate through MokaHow 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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In Regione Emilia – Romagna Moka will

Catalog

OpenData

OraganizeSDI

• GeoData• RDBMD and tables• Web services• Metadata (RNDT, Metadata RER)• OpenData• Functions and appications

Create applicatio

ns with data and OpenData

• Web Applications• Desktop Applications• Apps for smartphone

• Uses GetLOD services

Create

OpenData

SDI and OpenData will interoperate through Moka

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 esplicitoApplicazione sopra il modello concettuale esplicitoApplicazione sopra il modello concettuale esplicitoApplicazione 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

Towards Linked Open geo-Data

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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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 fileGetLOD

MD catalogoOpen Data

Catalogo

catalogazione

Ricerca

API

GetLOD: Open GeoData Solution

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:

3. UUID are not URI friendly

4. 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

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1. Identification &

dataset selection

1. Identification &

dataset selection

6.validation

6.validation

7.release

7.release

2.cleaning up

2.cleaning up

3.analysis & modeling

3.analysis & modeling

4.enrichmenet

4.enrichmenet5.

external linking

5.external linking

LOD Life CycleLOD Life Cycle

Source“Linee Guida per l’Interoperabilità Semantica attraverso i Linked Open Data” (Agenzia per l'Italia Digitale)

GetLOD: solution that implements the entire LOD Life Cycle

GetLOD: Open GeoData Solution

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ShapeFileGMLXML metadata ISO 19115 (RNDT compliant)XML describing OpenData

RDF for DataRDF for Metadata ISO 19115 (RNDT compliant)XML describing Linked Open Data

Generate OpenData

Generate Linked OpenData

GetLOD: Open GeoData Solution

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GetLOD: Open GeoData Solution

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GetLOD RDF Browser integrates:

GeoER-APIRDF Administrative boundaries, Buildings, Road Toponyms, Civic NumbersEvents from E-R Culture(http://dati.emilia-romagna.it/dato/item/37-37-eventi-e-r-cultura.html?goback=.gmp_3816349.gde_3816349_member_203780094)Query Endpoint SPARQL

GetLOD: Demo

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In 2014 we will focus on:

• Interoperability: In Regione Emilia – Romagna SDI and LOD infrastructures will interoperate through Moka

• Interlinking: to compare entities from different datasets available as LOD and calculate similarities through textual, geographical and temporal distance to match

• Natural browsing: to integrate the existing map viewer with navigation and browsing of Linked Open Data

GetLOD: Evolution in 2014

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GetLOD: Evolution in 2014

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Thanks for your attention!

StefanoPezzi@sinergis.itMassimoZotti@planetek.it

GCiardi@regione.emilia-romagna.itMFustini@regione.emilia-romagna.it