Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013 June 23 Florence, Italy Strabon Semantic support for EO Data Access in TELEIOS Dept. of Informatics and Telecommunications National and Kapodistrian University of Athens Presenter: George Garbis
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Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
June 23 Florence, Italy
Strabon
Semantic support for EO Data Access in TELEIOS
Dept. of Informatics and Telecommunications National and Kapodistrian University of Athens
Presenter: George Garbis
2 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Outline
Motivation
Representing and Querying Geospatial and Temporal Information in RDF
Applications
The Fire Monitoring Service of the National Observatory of Athens
The TerraSAR-X Virtual Observatory of the German Aerospace Center
Thoughts for discussion
3 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Catalogue
Processing Chains
EO data center
Archive
State of the Art in EO Data Centers
Raw Data
Users
EOWEB
4 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Example
Can I pose the following query using EOWEB?
Find images taken by the SEVIRI satellite on August 25, 2007 which contain fire hotspots in areas which have been classified as forests according to CORINE Land Cover, and are located within 2km from an archaeological site in the Peloponnese.
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Example (cont’d)
6 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Example (cont’d)
Well, only partially.
Find images taken by the SEVIRI satellite on August 25, 2007 which contain fire hotspots in areas which have been classified as forests according to CORINE Land Cover, and are located within 2km from an archaeological site in the Peloponnese.
7 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Example (cont’d)
But why?
All this information is available in the satellite images and other auxiliary data sources of EO data centers or on the Web.
However, EO data centers today do not allow:
mining of satellite image content and
its integration with other relevant data sources so the previous query can be answered.
8 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
High Level Data Modeling
Need for representing
Standard product metadata
Standard product semantic annotations
Geospatial information
Temporal information
Need to link to other data sources
GIS data
Other information on the Web
9 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Semantics-Based Representation and Querying of EO Data
The data model stRDF and the query language stSPARQL
The system Strabon
10 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
Outline
Motivation
Representing and Querying Geospatial and Temporal Information in RDF
Applications
The Fire Monitoring Service of the National Observatory of Athens
The TerraSAR-X Virtual Observatory of the German Aerospace Center
Conclusions
11 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
RDF: Resource Description Framework
W3C recommendation
RDF is a graph data model ( + XML syntax + semantics)
For representing metadata
For describing the semantics of information in a machine-readable way
Resources are described in terms of properties and property values using RDF statements
Statements are represented as triples, consisting of a subject, predicate and object.
11
"23.7636"^^xsd:double noa:hasArea
ex:BurntArea1
12 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
The Data Model stRDF
stRDF stands for spatial/temporal RDF.
It is an extension of the W3C standard RDF for the representation of geospatial data that may change over time.
stRDF extends RDF with:
Spatial literals encoded in OGC standards Well-Known Text or GML
New datatypes for spatial literals (strdf:WKT, strdf:GML and strdf:geometry)
Temporal literals can be either periods or instants
New datatype for temporal literals (strdf:period)
Placed as the fourth component of a triple to denote valid time
13 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stRDF: An example (1/2)
14 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stRDF: An example (1/2)
ex:BurntArea1
15 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stRDF: An example (1/2)
rdf:type ex:BurntArea1
noa:BurntArea
16 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stRDF: An example (1/2)
“1” ^^xsd:int noa:hasID
rdf:type ex:BurntArea1
noa:BurntArea
17 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stRDF: An example (1/2)
“1” ^^xsd:int
"23.7636"^^xsd:double noa:hasArea
noa:hasID
rdf:type ex:BurntArea1
noa:BurntArea
18 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
"POLYGON(( 38.16 23.7, 38.18 23.7, 38.18
23.8, ... 38.16 23.8, 38.16 3.7));
<http://spatialreference.org/ref/epsg/4121/>"
^^strdf:WKT
stRDF: An example (1/2)
“1” ^^xsd:int
"23.7636"^^xsd:double noa:hasArea
noa:hasID
rdf:type ex:BurntArea1
noa:BurntArea
geo:geometry
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"POLYGON(( 38.16 23.7, 38.18 23.7, 38.18
23.8, ... 38.16 23.8, 38.16 3.7));
<http://spatialreference.org/ref/epsg/4121/>"
^^strdf:WKT
stRDF: An example (1/2)
Spatial Data Type Well-Known Text
“1” ^^xsd:int
"23.7636"^^xsd:double noa:hasArea
noa:hasID
rdf:type ex:BurntArea1
noa:BurntArea
geo:geometry
20 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
"POLYGON(( 38.16 23.7, 38.18 23.7, 38.18
23.8, ... 38.16 23.8, 38.16 3.7));
<http://spatialreference.org/ref/epsg/4121/>"
^^strdf:WKT
stRDF: An example (1/2)
Spatial Data Type Well-Known Text
“1” ^^xsd:int
"23.7636"^^xsd:double noa:hasArea
noa:hasID
rdf:type ex:BurntArea1
noa:BurntArea
geo:geometry
Spatial Literal (OpenGIS Simple
Features)
21 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
22 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
23 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
24 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
25 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
26 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
27 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:hasGeometry ?RGEO .
?R noa:hasCorineLandCoverUse . .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:hasGeometry ?CGEO .
?BA rdf:type noa:BurntArea .
?BA geo:hasGeometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)}
• Find all burned forests within 10kms of a city
stSPARQL: An example (1/2)
Spatial Functions (OGC Simple Feature Access)
28 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stSPARQL: An example (1/2)
29 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
33 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:geometry ?RGEO ;
?R noa:hasCorineLandCoverUse ?F ?t1. .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:geometry ?CGEO .
?BA rdf:type noa:BurntArea ?t2.
?BA geo:geometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)
FILTER( strdf:during(?t1, “[2006-01-01:00:00:01,
2006-01-01:23:59:59]”^^strdf:period)) &&
strdf:before(?t1, ?t2) }
Find all areas that were forests in 2006 and got burned later within 10kms of a city
stSPARQL: An example (2/2)
34 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:geometry ?RGEO ;
?R noa:hasCorineLandCoverUse ?F ?t1. .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:geometry ?CGEO .
?BA rdf:type noa:BurntArea ?t2.
?BA geo:geometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)
FILTER( strdf:during(?t1, “[2006-01-01:00:00:01,
2006-01-01:23:59:59]”^^strdf:period)) &&
strdf:before(?t1, ?t2) }
Find all areas that were forests in 2006 and got burned later within 10kms of a city
stSPARQL: An example (2/2)
35 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
SELECT ?BA ?BAGEO
WHERE { ?R rdf:type noa:Region .
?R geo:geometry ?RGEO ;
?R noa:hasCorineLandCoverUse ?F ?t1. .
?F rdfs:subClassOf clc:Forests .
?CITY rdf:type dbpedia:City .
?CITY geo:geometry ?CGEO .
?BA rdf:type noa:BurntArea ?t2.
?BA geo:geometry ?BAGEO .
FILTER( strdf:intersect(?RGEO,?BAGEO) &&
strdf:distance(?RGEO,?CGEO,uom:km)<10)
FILTER( strdf:during(?t1, “[2006-01-01:00:00:01,
2006-01-01:23:59:59]”^^strdf:period)) &&
strdf:before(?t1, ?t2) }
Find all areas that were forests in 2006 and got burned later within 10kms of a city
stSPARQL: An example (2/2)
Temporal extension functions
36 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stSPARQL: An example (2/2)
37 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stSPARQL: More details
We start from SPARQL 1.1.
We add a SPARQL extension function for each function defined in the OGC standard OpenGIS Simple Feature Access – Part 2: SQL option (ISO 19125) for adding geospatial data to relational DBMSs and SQL.
We add a set of temporal functions (superset of Allen’s functions) as SPARQL extension functions
We add appropriate geospatial and temporal extensions to SPARQL 1.1 Update language
38 Exploiting the Integration Potential of Semantic Web and Linked Data Technologies for Geospatial Applications, Workshop in INSPIRE Conference 2013
stSPARQL vs. GeoSPARQL
GeoSPARQL is a recent OGC standard to develop an extension of SPARQL for querying geospatial data expressed in RDF.
stSPARQL and GeoSPARQL have been developed independently.
stSPARQL geospatial query functionality is very close to a subset of GeoSPARQL: