GetLOD - Linked Open Data and Spatial Data Infrastructures W3C Linked Open Data LOD2014 Roma, 20-21 February 2014 Stefano Pezzi, Massimo Zotti, Giovanni Ciardi, Massimo Fustini
Agenda Context Geoportal & OpenData Portal SDI management Towards Linked Open geoData GetLOD: Open GeoData Solution 2
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: Open GeoData Solution 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 5
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 Moka How Moka (CMS GIS) helps users to create OpenData through GetLOD From Moka users can manage the update of Open Data 5 In Moka Catalog user selects the geodata to Open Data are catalogued 4 1 be published as Open in Moka repository Data 2 3 Moka Catalog invokes GetLOD services to create Open Data
SDI and OpenData will interoperate through Moka In Regione Emilia – Romagna Moka will • GeoData Create • • RDBMD and tables Web Applications applications Oraganize • • with data Web services Desktop Applications SDI and • • Metadata (RNDT, Metadata RER) Apps for smartphon e OpenData • OpenData • Functions and appications Catalog Create • Uses GetLOD O penData OpenData services
Towards Linked Open geo-Data 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! 15
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.
Towards Linked Open geo-Data Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Applicazione sopra il modello concettuale esplicito Application over conceptual model L'integrazione a livello di dati L'integrazione a livello di dati Integration at the level data 17
GetLOD: Open GeoData Solution 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). 18
GetLOD: Open GeoData Solution 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 ) 19
GetLOD: Open GeoData Solution LOD Front-end Download Ricerca RDF JAVA LOD Back-end Triple server dump API connettori catalogazione MD catalogo Catalogo TripleStore mapping API Open Data GetLOD file www OGC WFS OGC CSW GI Middleware OGC server MD server GI Data & Metadata GeoRepository MD 19115 20
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. 21
GetLOD: Open GeoData Solution 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 • ... 22
GetLOD: Open GeoData Solution 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… 23
GetLOD: Open GeoData Solution Geometry 1. LOD data are especially used in mash up apps that likely use common maps APIs WGS84 instead of official regional SRS 24
GetLOD: Open GeoData Solution 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 25
GetLOD: Open GeoData Solution 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. 26
GetLOD: Open GeoData Solution Geometry 4. Standards are important, but does anyone already use them? Use “OGC GeoSparql”, but even “WGS84” Redundancy is not a problem in LOD 27
GetLOD: Open GeoData Solution 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 28
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