Presentation at the Topometry Lab (TOPO) at the EPFL (Ecole Polytechnique Fédérale de Lausanne) February 2011, Lausanne, Switzerland

1. PresentationAna ROXIN

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Presentation outlook

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Spatial Information Infrastructures
Semantic Web
Spatial Semantic Web
Introduction
3

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Introduction – Spatial Information Infrastructures
4
Goals
• Discover resources (data and
services)
• Access data (for both vector
and coverage data)
• Use data
• Visualize data according to
given rules
• Harmonize and integrate data
• Orchestration
Challenges
• Inconsistent data
• Naming conflicts
• Scale conflicts
• Precision or resolution
conflicts
• Constraint conflicts
• Data value conflicts
• Multilinguality
• Multiple representations
• Reference systems and units of
measure
• Etc.

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Introduction – The Semantic Web

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Introduction – The Spatial Semantic Web
Spatial data community
• Ontologies for describing spatial data
• Formally defined and shared semantics
• Handling of heterogeneous spatial
features
Semantic Web community
• Spatial information as a context provider
• Data validity
• Temporal information

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Semantic Web Technologies for Information
Infrastructures

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A growing demand for interoperability
< 1970s
• Mainframe computing
• Centralized perspective
1980s
• First revolution: advent of personal computer
• Data interoperability becomes an issue
1990s
• Second revolution: advent of Internet
• Need for more principled mechanisms to ensure
interoperability

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Different layers of interoperability
• Concerns bottom layers of ISO/OSI network hierarchy;
• Solved through hardware standards (Ethernet) and protocols (TCP/IP and HTTP).
Physical interoperability
• Concerns the syntactic form of exchanged messages;
• Realized through XML and syntactic standards (HTML, WSDL, SOAP)
Syntactic interoperability
• Concerns the meaning of messages and Web pages;
• Allows automatic machine processing of information (selection, composition,
reasoning).
Semantic interoperability

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Ontologies as building bricks for the Semantic Web
• Explicit and shared specification of a conceptualization of a given
knowledge domain
(T. R. Gruber. Toward principles for the design of ontologies used for knowledge sharing.
Presented at the Padua workshop on Formal Ontology, March 1993)
Ontology definition
• Establish robust theoretical foundations for geographic information
science
• Three sets of foundational issues :
• Conceptual issues;
• Representational and logical issues;
• Implementation issues.
Ontologies for geographical information
science

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Ontology languages

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Flavors of semantic interoperability
• Minimal shared amount of information – the fact expressed in the statement itself
• Enabled by RDF (Resource Description Format)
• Ex: Object “Berne” is related to object “Switzerland” by “being its capital”.
Minimal semantic interoperability
• Minimal set of beliefs on what two agents may infer after having exchanged a sentence
• Enabled by RDF Schema
• Ex: Shared ontology defining that capitals are cities, capitals are unique, etc.
Extended semantic interoperability
• Lower bound + upper bound on what agents may not believe after exchanging a sentence
• Enabled by OWL (Web Ontology Language)
• Ex: OWL shared ontology forbidding the belief of Zurich is also a Swiss capital.
Full semantic interoperability

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Building bricks of the Semantic Web architecture

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RDF Ressource Description Framework
 An RDF document is structured as an ensemble of triplets
 An RDF triplet is an association {subject, predicate, object}
 An RDF document is a labeled and oriented graph.
Object – Author ROX639
URI – http://www.gsem.fr/authors#ROX639
Predicate – Creator
URI – http://purl.org/dc/elements/1.1/creator
Subject – Document no42305
URI – http://www.gsem.fr/documents#D42305

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OWL Web Ontology Language
 Extension of RDF/RDFS languages
 Adds new concepts
 Specialization of RDF constructs

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Example – DBpedia Relation Finder
http://relfinder.dbpedia.org/relfinder.html

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Works related to semantics in geospatial information
2000
• Bishr - Ontology-based information modeling provides more cognitive
foundation for information systems models + minimizes the problem of
semantic heterogeneity.
2001
• Smith - Ontology of geographical categories – a catalogue of the prime
geospatial concepts and categories shared in common by human subjects.
2003
• Hakimpour et al. - Architecture and methodology for geographical schema
integration based on DL reasoning on sources ontologies and global schemas
• Fonseca et al. – Formal framework mapping spatial ontologies to geographic
conceptual schemas

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Works related to semantics in geospatial information
2004
• Hess and Iochpe – Methodology for semantic integration of geographic
conceptual schemas;
• Rodriguez and Egenhofer – Technique for calculating semantic similarity
among spatial entities (Matching Distance Similarity Measure).
2005
• Schwering and Raubal – Query method based on spatial relations for
integration of information sources (shared vocabulary mapped to ontologies);
• Sotnykova et al. – Methodology for integration of spatio-temporal schemas,
based on the MADS-compliant source ontology (translated into OWL DL).
2006
• Stoimenov et al. – Implementation of semantic mediators acting access points
for several independent geoinformation sources;
• Aerts et al. – Methodology for topographic databases integration based on
OWL ontologies.

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Works related to semantics in geospatial information
2008
• Xu et al. – Algorithm for automatic geospatial service composition based on
WordNet ontology dictionary;
• Tang et al. – Methodology for conceiving geographic information ontologies, and
proposition of an ontology-based discovery protocol for geographic information.
2009
• Van Hage et al. – Open-source SWI-Prolog extension providing spatial indexing
capabilities and spatial/semantic query integration;
• Janowicz et al. – Outline the need for a Semantic Enablement Layer for OGC
services, and establish steps towards its establishment.
2010
• Parundekar et al. – Algorithm for aligning ontologies of geospatial sources (use of
subsumption/equivalence relations and conjuction/restriction classes);
• Wick et al. – Version 2.2.1 of the GeoNames Ontology (over 6.2 million
geonames toponyms with an unique URI)

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Example – GeoNames Ontology
http://www.geonames.org/

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Example – DBpedia Mobile
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Main features Illustration

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Semantics for Services within Spatial Information
Infrastructures

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Semantic modeling considerations for geoservices
• Common ground of ontological concepts to which semantic descriptions of
services should refer.
Semantic interoperability frameworks
• Geoservices perform geo-operations on various representations of features
(spatial, temporal and thematic dimensions)
Geoservices
• Ontology-based :
• Classification of geo-operation functionality;
• Description of operation input and output parameter types;
• Description of geodata that are tightly coupled to the service;
• Description of the control flow in (virtual) composite operations.
Semantic description of geoservices

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The OWL-S ontology
Discovery
InteractionExecution

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Semantic Interoperability Framework for Geoservices
– SIFGEO
Operations that match
a set of input and/or
output parameter types
Operations that fit an
existing service chain
with respect to their
input and/or output
parameter types
Operations that are
composed of
operations that
instantiate a given set
of operation types
Information/service
concepts that are sub-
or super-classes of a
given concept
Data sets that contain a
specific feature type
Feature
concept
Concepts for
real-world
phenomena
and their
relations
ISO 19110
(Methodology
for Feature
Cataloguing)
standard
Feature
symbol
Elements
forming a
feature at a
symbol level
and their
relations
ISO General
Feature Model
Geo
operation
Operation
types (behavior
+ input/ output
parameters) +
control flow
elements =
OPERA
ISO 19119
(Services)
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Typical queries (Find all…) Framework formal ontologies

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Example – SIFGEO for the Java volcano eruption – 1
 Scope: create a service chain to identify the extent of mud eruption
 Input: 3 SPOT images from the volcano eruption
 Step 1: Creating the services
SPOT image 1 SPOT image 2 SPOT image 3
Band rationing service
= distinguish land-mud
boundaries
Slicing service
= land-mud pixels’
classification
Cross service
= combining land-mud
coverages into one
Impact service
= impact area calculus
for 2 eruption periods

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Example – SIFGEO for the Java volcano eruption – 2
 Step 2: Linking services to the OPERA ontology
 Step 3: create the OWL-S description for the service chain
Band rationing service
->
opera:CrossCalculate
Slicing service
-> subclass of
opera:Classify
Cross service
->
opera:CrossConcatenate
Impact service
-> subclass of
opera:Group
EvaluateEruption ≡ ServiceChain
<ServiceChain>
BandRationing isOfType opera:CrossCalculate
Slicing isOfType opera:Classify
Cross isOfType opera:CrossConcatenate
Impact isOfType opera:Group
</ServiceChain>


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Example – Extending OWL-S for context-aware
semantic Web service discovery – 1
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Service
Service
Profile
Service
Model
Service
Grounding
Service
Context
ECommerce
Service
xsd:float
Information
Service
Personal
Service
Emergency
Service
xsd:boolean
hasValue*

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Example – Extending OWL-S for context-aware
semantic Web service discovery – 2

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Geographic
information
• Development of SII
• Risk of condemning
the GI community to
a specialist
backwater.
• Semantic Web
technologies
• Useful, interesting
• Difficult to integrate
• Geosemantic
interoperability relies
on standards
Geosemantics
• Geo ontology
• Feature ontology
• Feature type ontology
• Spatial relationship
ontology
• Toponym ontology
• Coordinate
reference/spatial
index ontology
• Geodata
set/metadata
ontology
• Spatial services
ontology
Standardization
• Critical for SII
• SII must support the
evolution of
geosemantics
• Geosemantic
standards are not
completely “hopeless
without,” but they are
at least quite urgently
“nice to have.”
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Conclusion and perspectives

35. Contact information:
ana-maria.roxin@u-bourgogne.fr