Ontological Engineering for the Cadastral Domain

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Ontological Engineering for the Cadastral Domain

• Erik Stubkjær,
• Aalborg University
• Heiner Stuckenschmidt, University of Bremen

With contributions from Michel Klein, Frank
van Harmelen and Dieter FenselFree University
Amsterdam
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Ouline of the Talk

• Why Ontologies ?
• Ontological Engineering
• Capture ? The Cadastral Domain
• Modeling ? Requirements for Languages
• Integration ? Examples from he Cyc-Ontology
• Implementation ? Ontologies and XML
• Outlook Ontologies on the World-Wide-Web

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Problems of Information Management

• With the large number of information sources
  several information management systems arose.
  However these systems have severe weaknesses
• Word matching as search method
• Information Retrieval instead of Query Answering
• Information exchange is only possible with severe
  effort.
• Different views on information is not supported.

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Ontologies and their Applications

• What are Ontologies

An Ontology is an explicit specification of a
conceptualization

• Benefits of Ontologies
• Explication
• Formalization
• Standardization
• Communication

• Applications Areas
• Teaching and Learning
• Systems Design
• Consistency Checking
• Interoperability

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Potential Benefits of Ontolgies

• Ontologies will allow structural and semantic
  definitions of documents providing completely new
  possibilities!
• Intelligent search instead of keyword matching.
• Query Answering instead of Information Retrieval.
• Information exchange via transformation
  operators.
• Definition of views on information sources.

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Capture The Cadastral Domain
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Modeling Requirements for Languages

• Well defined syntax (pretty obvious)
• read ontologies
• Well defined semantics
• often overlooked but equally important
• process (understand) ontologies
• Expressive enough
• to capture many ontologies
• Easy mapping (for integration)
• to/from other ontology languages
• Efficient reasoning support

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Why Reasoning Support?

• Important
• as design support tool
• for large ontologies
• with multiple authors
• for integrating and sharing ontologies
• Because it allows to
• Establish inter-ontology relationships
• Check for consistency
• Check for (unexpected) implied relationships
• Shown useful for DB schema integration

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Sidetrack OIL as example

• OIL Ontology Inference Layer
• modelling primitives from frames (OKBC-lite)
• semantics and inference from Description Logic
• several syntaxes from W3C languages

• OIL only used as example to show procedures
• applicable to other ontology languages as well

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Integration Examples from the Cyc-Ontology

• The Cyc Project (www.cyc.com)
• Aim Capture Human CommonSense Knowledge
• Results Huge Repository of Commonsense Theories
• Applications Information Integration and
  Retrieval
• Examples of relevant concepts in Cyc
• Geography, Spatial Relations
• Agents, Actors
• Organizations, Professions 
• Agreements, Transfer Of Possession

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Example The Concept Spatial Thing
SpatialThing   The collection of all
things that have a spatial extent or location
relative to some other SpatialThing. Note well
that to say that an entity is a member of this
collection is to remain agnostic about two
issues. First, a SpatialThing may be
PartiallyTangible, like Texas-State or wholly
Intangible, like the ArcticCircle or a line
or a plane referenced in a geometric theorem.
Second, although we do insist on location
relative to another SpatialThing, a
SpatialThing may or may not be located in the
physically observable universe. It is far from
clear that all SpatialThings are so located
eg, a trajectory through the phase space of some
physical system. If the intent is to imply
location in the empirically observable cosmos,
the user should employ this collection's spec,
SpatialThing-Localized. isa ObjectType
genls Individual some subsets
RadiallySymmetricObject BilaterallySymmetricOb
ject Surface-Generic Border GeometricThing
PureSpace ClothingItem Surface-Abstract
Surface-Physical Angle TwoDimensionalShape
Line FrameOfReference ThreeDimensionalShape
AbstractShape (plus 898 more public subsets,
11848 unpublished subsets)
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Example Transferring Posession
TransferringPossession   A collection of
events. In an instance of TransferringPossession
, the possession of a single object (i.e., the
objectOfPossessionTransfer) is transferred from
one Agent to another. Thus, a
TransferringPossession event alters the rights
of TWO different agents to use the object in
question one agent loses some UserRightsAttribu
te over it, while the other agent gains some
UserRightsAttribute over it. Each
TransferringPossession event is both a
LosingUserRights event and a GainingUserRights
event. isa DefaultDisjointScriptType
ScriptType TemporalObjectType genls
SocialOccurrence GainingUserRights
LosingUserRights some subsets
MoneyTransfer BorrowingSomething
TakingCustodyOfAnimal Stealing-Generic
MoneyTransaction GivingSomething
TransferringOwnership Paying
ArrestingSomeone Trapping MonetaryExchangeOf
UserRights GiftGiving Buying Renting
SaleByCreditCard (plus 1 more public subset,
54 unpublished subsets)
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Example The Concept Real-Estate
RealEstate   A collection of tangible
objects. Each element of RealEstate is either a
parcel of land or a land-based property that can
be bought, sold, or rented. This includes
buildings and parts of buildings such as office
suites or condominiums, as well as parcels of
land. Some prominent examples GuantanamoNavalBa
se, NewYorkHiltonAtBroadway, WorldTradeCenter.
isa ProductType ExistingObjectType
genls SolidTangibleProduct some
subsets Building GroundsOfOrganization
RailroadStation-Physical ThreeStoryBuilding
TwoStoryBuilding OneStoryBuilding
ModernShelterConstruction ModernHumanResidence
SingleResidenceUnit (plus 1 more public
subset, 80 unpublished subsets)
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Implementation Extensible Markup Language

• XML Document Labeled Tree, Nodes contain
  information
• DTD simple grammars to describe legal trees

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XML limitations for semantic markup

• XML makes no commitment on
• Domain specific ontological vocabulary
• Ontological modelling primitives
• ? requires pre-arranged agreement on ? ?
• Only feasible for closed collaboration
• agents in a small stable community
• pages on a small stable intranet
• not for sharable Web-resources

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XML Schema introduction (1)

• XML Schema has same function as DTD
• prescribes document structure
• but has some advantages
• XML Schema is XML itself (also namespaces)
• simple datatyping
• richer grammar
• type hierarchy with derivation

ltcomplexType name"CountryType"gt ltelement
name"Name" type"string"/gt ltelement
ref"Capital"/gt lt/complexTypegt
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XML Schema (2) richer grammar

• content models
• grouping, by choice, sequence or all
• cardinality
• attributes minOccurs, maxOccurs
• defaults and constants
• attributes default, fixed

ltcomplexType name"WindowsType"gt ltelement
name"version" type"string minOccurs"0
maxOccurs"1" default"W98"/gt ltelement
name"includedBrowser" type"string
minOccurs"0" maxOccurs"1" fixed"Internet
Explorer"/gt lt/complexTypegt
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XML Schema (3) type hierarchy

• two types of derivation
• derived by extension
• derived by restriction
• no multiple inheritance
• derivation hierarchy is NOT a class hierarchy
• inheritance is either restricting or extending
• instances are not automatically instance of
  supertype

ltcomplexType nameprice" base"decimal"
derivedBy"extension"gt ltattribute
name"currency" type"string"/gt lt/complexTypegt ltc
omplexType nameUSaddr" base"address"
derivedBy"restriction"gt ltelement name"country"
fixed"US"/gt lt/complexTypegt
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Benefits of using an ontology on top of XML Schema

• expressive modeling constructs (intentional
  types) can be used to model XML data
• document structure is grounded on a true semantic
  basis
• conceptual layer on top of XML data to facilitate
  higher level access, abstracted from document
  structure

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Derive XML Schema from ontology
class-def Country_Comparison
slot-constraints compared_to
value-type Country proportion
value-type STRING

• primitives
• class, slot
• value-type, etc

• XML Schema
• primitives
• complexType

used in
used in
ontology
XML schema
translate to
(formatted) Area -- comparative slightly less
than twice the size of New Jersey. Capital
Amsterdam The Hague is the seat of government.
prescribes structure
XML documents
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Conceptual layer
Conceptual access SELECT Name FROM Country
Conceptual access value this.country.name
ontology
Relational schema
system
system
XML Schema
Direct access ltxslvalue-of select"parent /p
arent/_at_name"/gt
database block 232 block 234 block 259
block 271 block 292 block 308
Direct access (string)readNext(block)
XML documents ltcountrygtltnamegtTheNetherlandslt/name
gtltcapitalgtAmsterdamlt/capitalgtlt/countrygt
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How to put ontologies on the Web(internet,
intranet, extranet)
The W3C hierarchy of languages
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RDF(S) general background

• Intended for representation meta-data,basis
  for Web-based ontology-language
• W3C recommendation
• Because its there
• pushed hard by W3C (TBL Himself)
• basis of 80M DAML program
• Already embraced by some vendors(Netscape)

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Bluffers guide to RDF (1)

• Object --Attribute-gt Value triples
• objects are web-resources
• Value is again an Object
• triples can be linked
• data-model graph

Author-of
Author-of
Publ-by
Publ-by
Author-of
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Bluffers guide to RDF (2)

• Object --Attribute-gt Value triples
• objects are web-resources
• triples can be linked
• data-model graph
• Any statement can be an object
• graphs can be nested

Thats all there is to it.
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Bluffers guide to RDF Schema

• So, RDF
• (very small) commitment to modelling primitives
• but no commitment to domain vocabulary
• RDF Schema
• Define vocabulary for RDF
• Organise this vocabulary in a typed hierarchy
• Class, SubClassOf, type
• Property, subPropertyOf,
• domain, range

Thats all there is to it.
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RDF Schema syntax in XML
ltrdfDescription ID"MotorVehicle"gt ltrdftype
resource"http//www.w3.org/...Class"/gt
ltrdfssubClassOf rdfresource"http//www.w3.org/.
..Resource"/gt lt/rdfDescriptiongt ltrdfDescrip
tion ID"Truck"gt ltrdftype resource"http//ww
w.w3.org/...Class"/gt ltrdfssubClassOf
rdfresource"MotorVehicle"/gt lt/rdfDescriptiongt
ltrdfDescription ID"registeredTo"gt
ltrdftype resource"http//www.w3.org/...Property
"/gt ltrdfsdomain rdfresource"MotorVehicle"/
gt ltrdfsrange rdfresource"Person"/gt lt/rdfD
escriptiongt ltrdfDescription IDownedBy"gt
ltrdftype resource"http//www.w3.org/...Property
"/gt ltrdfssubPropertyOf rdfresource"registe
redTo"/gt lt/rdfDescriptiongt
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Ontologies as RDF(S) extension (1/2)
ltrdfsClass rdfIDherbivoregt ltrdftype
rdfresourcehttp//www.ontoknowledge.org/
DefinedClass/gt ltrdfssubClassOf
rdfresourceanimal/gt ltrdfssubClassOfgt
ltoilNOTgt ltoilhasOperand
rdfresourcecarnivore/gt lt/oilNOTgt
lt/rdfssubClassOfgt lt/rdfsClassgt
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Ontologies as RDF(S) extension (2/2)
RDF(S)
OIL

• class-expressions
• AND, OR, NOT
• slot-constraints
• has-value, value-type
• cardinality
• slot-properties
• trans, symm

• class-def
• subclass-of
• slot-def
• subslot-of
• domain
• range