20130905_Feng_Chia_GIS_center_geospatial_ontology

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Geo-Ontology and -Semantics:
From Theoretics to Practices
Institute of Information Science, Academia Sinica
Faculty of Geo-Information Science and Earth Observation (ITC),
University of Twente
Dongpo Deng
dongpo.deng@gmail.com
Tuesday, September 10, 2013

What is ‘O’ntology?
• The term originated from a philosophical discipline
• A branch of philosophy that deals with the nature and the
organization of reality
• It was defined by Aristotle in Metaphysics, IV, 1
• It tries to answer the questions:
• What is being?
• What are the features common to all beings?
• How should things be classified?
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What is ‘o’ntology?
• a specification of a conceptualization (Gruber, T. 1993)
• a formal specification of a shared conceptualization (Borst et
al., 1997)
• is a hierarchically structured set of terms for describing a
domain that can be used as a skeletal foundation for
knowledge base (Swartout et al., 1996)
• the method to extract a catalogue of things or entities (C)
that exist in a domain (D) from the perspective of a person
who use a certain language (L) to describe it (Sowa, 2000)
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What is ‘o’ntology?
• From AI perspective (Agarwal, 2005)
• “conceptualization” is explained as an abstract model of some
phenomenon in the world by having identified the relevant concepts
of that phenomenon.
• “explicit” means that type of concepts used and the constraints on
their use are explicitly defined
• “formal” refers to the fact that the ontology should be machine-
readable
• “shared” refers to notion that on ontology captures consensual
knowledge
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An example of ontology description
• Example Vocabulary and meaning (“definitions”)
• A ‘Carnivore’ is a concept whose members are exactly those animals
who eat only meat
• A ‘Bear’ is a concept whose members are a kind of ‘Carnivore’
• A ‘Cub’ is a concept whose members are exactly those ‘Bear’ whose
age is less than one year
• A Panda is a individual of a ‘Bear’
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An example of ontology description
• Background knowledge/constraints on the domain (“general
axioms”)
• No individuals can be both a Herbivore and a ‘Carnivore’
• Each ‘Bear’ has a period of ‘Cub’
• The age of adult ‘Bears’ is at least 1 year old
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The meaning triangle
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Syntax-Semantics-Pragmatics
• Syntax (語法) deals with the study of relationships between
symbols
• Semantics (語意) analyzes the relationships between
symbols and things in the real world they denote (referent)
• Pragmatics (語用) goes beyond syntax and semantics, and
researches how symbols are used for particular purposes.
Thus, is analyzes relationships between symbols and specific
agents
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Ontologies for communication
Adapted by Maedche, 2001
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Ontology in Computer Science
• An ontology refers to an engineering artifact consisting of:
• A vocabulary used to describe (a particular view of) some domain
• An explicit specification of the intended meaning of the vocabulary
• almost always includes how concepts should be classified
• Constraints capturing additional knowledge about the domain
• Ideally, an ontology should:
• Capture a shared understanding of a domain of interest
• Provide a formal and machine manipulable model of the domain
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Why develop ontology?
• To share common understanding of the structure of
information among people or software agents
• To enable reuse of domain knowledge
• To make domain assumptions explicit
• To separate domain knowledge from the operational
knowledge
• To analyze domain knowledge
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Ontology spectrum
Logical Theory
Conceptual Model
Thesaurus
Taxonomy
is Disjoint Subclass of
with Transitivity
property
is Subclass of
has Narrower meaning
then
is Sub-Classification of
Model Logic
First Order Logic
Description Logic
DAML_OIL, OWL
UML
RDF/S
XTM
Extended ER
ER
DB Schemas, XML Schema
Relational Model, XML
strong semantics
weak semantics
Semantic Interoperability
Structure Interoperability
Semantic Interoperability
Syntactic Interoperability
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物種分類名錄 (taibif.tw)
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OpenStreetMap Map Features
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ADL Gazetteer Feature types
From http://www.alexandria.ucsb.edu/~lhill/
FeatureTypes/ver070302/00000250.htm
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ADL Gazetteer Feature types

From http://wordnetweb.princeton.edu/ 16

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The application ontology
inheriting GeoSPARQL

Edited by Protege
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Different kinds of ontologies and their
relationships
top-level ontology
very general concepts,
e.g. toopology,
mereology, geometry, ...
vocabularies related to a
generic domain by
specializing the top-level
ontologies, e.g. GeoSPARQL
domain ontology task ontology
application ontology
vocabularies related to a
generic task or activity by
specializing the top-level
ontologies, e.g. Semantic
Sensor Network (SSN)
ontology
concepts inheriting domain or
task ontologies for supporting
in certain activities, e.g. we
use SSN and GeoSPARQL to
create an ontology for
ecological observation
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Courtesy: Pascal Hitzler, GeoSemantics, 2009
Description Logics

Courtesy: Pascal Hitzler, GeoSemantics, 2009
Ontology and reasoning

What’s the (Geo) Problem?
• What’s special about Spatial?
• spatial-time-attributes
• What is geospatial interoperability?
• GML? WFS? or more alternatives?
• semantic Web - microformat tagging and (multiple) identity
• Semantic Web - (actionable) relationships and triple identity
• geosemantic - geotagging position
• Geosemantic - spatial(-temporal) theories, relationships,
mediations, transformations
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Adapted from J. Lieberman (2007) Geospatial Semantic Web: Is there life after geo:lat and geo:long ?

What’s the (Geo) Problem?
• Feature (type) and Geometry (representation)
• Model dependencies
• Community of discourse
• Scale
• Reference frame / coordinate system
• Perspective
• Geospatial plus other (semantic) dimensions
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Two approaches for studying on geo ontologies
• There are two distinct approaches that applied ontology in
GIScience.
• The philosophical approaches aim to identify specifications
of top-level categories from a formal ontology perspective,
• The domain-specific and task-oriented approaches focus on
explicating the actions, terms and relation for particular
specification and ranging from natural language to
rigorously formal specifications.
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How difficult to develop geospatial ontology?
• Geographic objects are typically complex, and they will in
every case have parts. (Simons, 1987; Smith and Mark,
1998)
• The geographic domain has specific issues regarding
ontology primarily because of its unstructured characteristics
• A standard terminology is not prevalent within the GIScience
domain and is dependent on the context of use and the user
• causes confusion in specification of universally accepted entities,
concepts, rules, relation, and semantics as the basis of a consensual
ontology.
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Geographical Entities are Indeterminate and
Ambiguous Objects
Philosophically speaking: Where does the
mountain begin and the valley end?
How can we derive a common
semantics which can refer accurately
to these kinds of objects?
B. Smith and D. Mark, 2003. Do Mountains Exist? Towards an Ontology of Landforms. Environment and Planning B, 30(3), 411-427
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Geospatial objects: vagueness and ambiguity
• Geographic categorization and classification are scale- and
size-dependent,
• regionalization in space and time is human-dependent, and
location and structure of boundaries shape many
geographical categories.
• The ways that space and time determine relations and property
inheritance are not yet clear.
• Human dependence means that geographic categories and
nomenclature can have different meanings in different application
contexts.
• fiat (tennis court) and bona fide (shoreline or riverbanks)
• open (bay) and closed (lake)
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B. Smith and D. Mark, 2003. Do Mountains Exist? Towards an Ontology of Landforms. Environment and Planning B, 30(3), 411-427

Conceptual model in General Feature Model (GFM)
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W3C Basic Geo Vocabulary
35http://www.w3.org/2003/01/geo/

Map4RDF
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http://oeg-dev.dia.fi.upm.es/map4rdf/

Geonames.org
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http://www.geonames.org/maps/google_25.048_121.532.html

‘Taipei’ in Geonames
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http://sws.geonames.org/1668341/about.rdf

Geonames ontology
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http://lov.okfn.org/dataset/lov/details/vocabulary_gn.html

Ordnance survey Ontologies
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http://data.ordnancesurvey.co.uk/ontology/

Spatial Relations in OS ontologies
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http://data.ordnancesurvey.co.uk/ontology/spatialrelations/contains

Spatial Relations in OS ontologies
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http://data.ordnancesurvey.co.uk/ontology/spatialrelations/contains.ttl

GeoSPARQL
• The GeoSPARQL will be a new OGC standard, which provides
three main components for encoding geographic information:
• (1) The definitions of vocabularies for representing features,
geometries, and their relationships;
• (2) A set of domain-specific, spatial functions for use in
SPARQL queries;
• (3) A set of query transformation rules
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Robert Battle, Dave Kolas, 2011. Enabling the Geospatial Semantic Web with Parliament and GeoSPARQL

Components of GeoSPARQL
• Vocabulary for Query Patterns
• Classes
• Spatial Object, Feature, Geometry
• Properties
• Topological relations
• Links between features and geometries
• Datatypes for geometry literals
• ogc:wktLiteral, ogc:gmlLiteral
• Query Functions
• Topological relations, distance, buffer, intersection, …
• Entailment Components
• RDFS entailment
• RIF rules to compute topological relations
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Courtesy from M. Perry (2012)The GeoSPARQL OGC Standard, Terra Cognita.

GeoSPARQL Vocabulary:
Basic Classes and Relations
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Details of ogc:wktLiteral
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Details of ogc:gmlLiteral
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Topological Relations between ogc:SpatialObject
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RCC8, Egenhofer & Simple Features
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Example Data
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Why Encode Geometry Data as a Literal?
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Why don’t GeoSPARQL support W3C Basic Geo?
• Too simple to meet our requirements
• Can’t use different datums and coordinate systems
• Limited number of geometry types
• W3C Basic Geo data can easily be converted to wktLiteral
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GeoSPARQL Query Functions
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GeoSPARQL Topological Query Functions
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GeoSPARQL Topological Query Functions
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Example Query
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GeoSPARQL RDFS Entailment Extension
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Simple Features Geometry Types
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GeoSPARQL Query Rewrite Extension
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GeoSPARQL Query Rewrite Extension
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Query Rewrite Rules
• Used to compute Feature-Feature spatial relations basedon
default geometries
• Specified as a collection of RIF rules
• Example: ogcr:sfEquals
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Summary of Conformance Classes
• Parameters
• Serialization
• WKT
• GML
• Relation Family
• Simple Features
• RCC8
• Egenhofer
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Determines geometry
classes and geometry
literal datatype
Determines topology
properties and topology
functions

Why don’t you support W3C Basic Geo?
• Too simple to meet our requirements
• Can’t use different datums and coordinate systems
• Limited number of geometry types
• W3C Basic Geo data can easily be converted to wktLiteral
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BBN Parliament
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An example query of GeoSPARQL(1)
• Within
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SELECT DISTINCT ?POO ?POO_wkt
WHERE {
?POO a eoe:PointOfObservation;
geo:hasGeometry ?POO_geo.
?POO_geo geo:asWKT ?POO_wkt.
FILTER (geof:sfWithin(?POO_wkt, "Polygon
((121 22, 121 23, 122 23, 122 22, 121
22))"^^sf:wktLiteral))
}

Query results (1)
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An example query of GeoSPARQ(2)
• buffer and within
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SELECT DISTINCT ?p_wkt?POO_wkt ?distance
WHERE {
?POO a eoe:PointOfObservation;
geo:hasGeometry ?POO_geo.
?POO_geo geo:asWKT ?POO_wkt.
geo:point_238918712815615_43904355280312
9 geo:asWKT ?p_wkt;
LET (?buff := geof:buffer(?p_wkt, 3000,
units:metre)) .
FILTER (geof:sfWithin(?POO_wkt, ?buff)) .
LET (?distance := geof:distance(?POO_wkt, ?
p_wkt, units:metre))
}

Query results (2)
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Q&A
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20130905_Feng_Chia_GIS_center_geospatial_ontology

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