Logical Foundation of the Semantic Web

1
???????? Logical Foundation of the Semantic Web
?? ??? Zhisheng Huang Vrije University
Amsterdam, The Netherlands huang_at_cs.vu.nl ?? ??
Wei Hu Southeast University whu_at_seu.edu.cn
2
?????Schedule
3
??4??????Lecture 4 The Semantic Web and its
Logics

• ????????
• RDF/RDFS
• OWL??
• OWL-DL??????????

4
?Google??starting from Google
5
?????Existing Problems
6
??????????Can we do it better?

• ???????Semantics-based search
• ?????? concept combination specification
• ?????? domain specific
• ???? approximate search
• ???? search agent

7
???(Semantic Web)

• ??????????????????, ????
• The Semantic Web is an extension of the current
  web in which information is given well-defined
  meaning, better enabling computers and people to
  work in co-operation. Berners-Lee et al.,
  2001

8
????????(What the Semantic Web wants to do)

• ???????
• ?????
• Content is machine-understandable if it is bound
  to some formal description of itself (i.e.
  metadata).

9
??? ?????WWW Its impacts and visions
10
??1.0 Web1.0
11
??2.0 Web2.0
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???3.0???Expectations on Web3.0
??????Web3.0?????

• ???(Novelty) ???????Web1.0?Web2.0???,????????????
  ???(??????Web1.0?Web2.0)

• ???(Achievability)??????????,??????????,
  ??????????????(??????Web4.0???)?

• ???(Urgency)?????????????????,???????????????
  ????(???????Web3.0)

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??3.0 Web3.0
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??1.0 ??2.0 ??3.0Web1.0 Web2.0 Web3.0

• ??1.0 ???
• Web1.0 Web of documents
• ??2.0 ??/???
• Web2.0 Web of persons
• ??3.0 ???
• Web3.0 Web of data (semantics)

15
???????
16
??????????????Advantages of Linked Data
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?????????

• ????????????,?????????,????????????
• ?????????????????,????????????????
• ?????????????,???????????
• ???????????Google???????????,???????????????,?????
  ,?????????????????????,???????????????????????

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???????????

• ???(Triple)?? ltsubject, predicate, objectgt
• ??ltzhishengHuang, isStaffof, VrijeUnivAmgt
• ???????????
• ??lthttp//wasp.cs.vu.nl/huang, isStaffof,
  http//www.vu.nlgt
• ?????????
• ????????????
• ???????????

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????????????

• ???ZhishengHuang???????????????????,????ZhishengH
  uang?????????
• ltZhishengHuang, isStaffof, VrijeUnivAmgt
• ltVrijeUniv, inCity,Amsterdamgt,
• lt?x, isStaffof, ?ygt,lt?y,inCity,?zgt
  -gtlt?x,worksin,?zgt
• ltZhishengHuang, worksin, Amsterdamgt

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??????Semantic Web and Ontologies
21
????????????? Why the Semantic Web?

• ????????????
• ?????????????????,???????????
• ?????????????????????????(????Triple/Tuple??)
• ???????????(????RDF/RDFS????????)
• ?????????????(????OWL?????????)
• (??RDF/RDFS/OWL???Triple????)

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????
????????????Gartner?2007?????,
?2012?,70?????????????????,20??????????????? Ga
rtner (May 2007) "By 2012, 70 of public Web
pages will have some level of semantic markup,
20 will use more extensive Semantic Web-based
ontologies
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??????????Ontologies and Metadata Billion
Triples dataset(????????)

• ????
• ??????
• ?????
• ??open??
• SemWebBase
• (DERI)
• ????
• ????
• ???
• ??????
• Freebase
• ??????

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Linked Data 2009
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????????????http//sindice.com/apiv2/search?q22
zhisheng20huang22formatatompage1qtterm
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????????????http//sindice.com/apiv2/search?q22
zhisheng20huang22formatatompage5qtterm
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Falcons
28
????????????
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More about the Semantic Web

• ??8?29? ??????
• 0900-1200 ??1Introduction to the Semantic
  Web(Ivan Herman)

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HTML??(HTML Markup)

• lth2gtZhisheng Huanglt/h2gt
• ltbgtAffiliationlt/bgt
• Department of Computer Scienceltbrgt
• Faculty of Sciencesltbrgt
• Vrije University Amsterdamltpgt
• ltbgtEmaillt/bgt huang _at_ cs.vu.nlltbrgt
• ltbgtPhonelt/bgt 31-20-4447740(office)
• lt/htmlgt

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XML?? XML-Annotations
ltresearchergtltnamegtZhisheng Huanglt/namegt ltaffiliati
ongt ltdepartmentgtDepartment of Computer
Sciencelt/departmentgt ltfacultygtFaculty of
Scienceslt/facultygt ltuniversitygtVrije University
Amsterdamlt/universitygt lt/affiliationgt ltemailgthuang
_at_ cs.vu.nllt/emailgt ltphone idofficegt
(31)-20-4447740lt/phonegt lt/researchergt lt/html
gt
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Data Structures

• ?????Structured Data
• Database
• ??????Semi-structured Data
• HTML, XML, BibTex
• ??????Non-structured Data
• Text

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??????XML??XML representation of a relational
database

• ltgroup nameAIgt
• ltmember id001gt
• ltnamegtJohnlt/namegt
• ltphonegt1234567lt/phonegt
• lt/membergt
• ltmember id002gt
• ltnamegtMarylt/namegt
• ltphonegt7654321lt/phonegt
• lt/membergt
• ..
• lt/groupgt

AI group
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??????Document Type Definition(DTD)

• lt!DOCTYPE researcher
• lt!ELEMENT researcher (name, affiliation, email,
  phone)gt
• lt!ELEMENT name (PCDATA)gt
• lt!ELEMENT email (PCDATA)gt
• lt!ELEMENT phone (PCDATA)gt
• lt!ATTLIST phone id CDATA REQUIRED gt
• lt!ELEMENT affiliation (department, faculty,
  university)gt
• gt

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????Data Model
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XML??XML Schema

• The purpose of an XML Schema is to define the
  legal building blocks of an XML document, just
  like a DTD.

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Why XML Schemas

• XML Schemas are extensible to future additions
• XML Schemas are richer and more useful than DTDs
• XML Schemas are written in XML
• XML Schemas support data types
• XML Schemas support namespaces

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????Name Conflicts

• Since element names in XML are not fixed, very
  often a name conflict will occur when two
  different documents use the same names describing
  two different types of elements.
• If these two XML documents were added together,
  there would be an element name conflict because
  both documents contain a same element with
  different content and definition.

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XML????XML NameSpace

• Using Namespaces to solve Name Conflicts
• Examples
• xmlnsnamespace prefix"namespace"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"

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????????? XML Schema
ltxsdelement name"reseracher"gt
ltxsdcomplexTypegt ltxsdelement name"name"
type"xsdString"/gt ltxsdelement
name"affiliation" type"affil" minOccurs"1"
maxOccurs"unbounded"/gt ltxsdelement
name"phone" type"xsdString"/gt ltxsdelement
name"email" type"xsdString"/gt
lt/xsdcomplexTypegt lt/xsdelementgt
ltxsdcomplexType name"affil"gt ltxsdelement
name " department" type"xsdString"/gt ltxsdelem
ent name " faculty" type"xsdString"/gt ltxsdele
ment name"university" type"xsdString"/gt
lt/xsdcomplexTypegt
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??????Resource Description Framework(RDF)

• Metadata is machine understandable information
  about web resources or anything that has an URI,
  it is represented as a set of independent
  assertions

ltrdfDescription about"http//wasp.cs.vu.nl/sekt/
dig/dig.pdf"gt ltdcCreator
rdfressource"http//www.cs.vu.nl/huang"/gt
ltdcCreator rdfressource"mailtoctv_at_cs.vu.n
l"/gt lt/rdfDescriptiongt
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RDF Dublin Core

• The Dublin Core provides properties for
  describing network objects, suitable for use by
  network search engines.
• The Dublin Core is a set of predefined properties
  for describing documents.
• The first Dublin Core properties were defined at
  the Metadata Workshop in Dublin, Ohio in 1995 and
  is currently maintained by the Dublin Core
  Metadata Initiative.

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Dublin Core Metadata Initiative

• The Dublin Core Metadata Initiative is an open
  forum engaged in the development of interoperable
  online metadata standards that support a broad
  range of purposes and business models.
• http//dublincore.org/

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Annotating Metadata

• ltrdfDescription rdfaboutdc-rdf/"gt
• ltdctitlegt
• Guidance on expressing the Dublin Core within
  the Resource
• Description Framework (RDF)
• lt/dctitlegt
• ltdccreatorgt Eric Miller lt/dccreatorgt
• ltdccreatorgt Paul Miller lt/dccreatorgt
• ltdccreatorgt Dan Brickley lt/dccreatorgt
• ltdcsubjectgt Dublin Core RDF XML
  lt/dcsubjectgt
• ltdcpublishergt Dublin Core Metadata
  Initiative lt/dcpublishergt
• ltdccontributorgt Dublin Core Data Model
  Working Group lt/dccontributorgt
• ltdcdategt 1999-07-01 lt/dcdategt
• ltdcformatgt text/html lt/dcformatgt
• ltdclanguagegt en lt/dclanguagegt
• lt/rdfDescriptiongt

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????????RDF Schema (RDFS)

• RDFS defines vocabulary for RDF
• Organizes this vocabulary in a typed hierarchy
• Class, subClassOf, type
• Property, subPropertyOf
• domain, range

46
RDFS
Prof. Qu
Hu,W
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Using A Blank Node

• Here the blank node stands for the concept of
  "John Smith's address".

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Blank Node Identifiers

• Blank nodes must have a name for triple usage.
• Blank node identifiers have the form _name
• exstaff85740 extermsaddress _johnaddress .
• _johnaddress extermsstreet"1501 Grant Avenue"
  .
• _johnaddress extermscity "Bedford" .
• _johnaddress extermsstate "Massachusetts" .
• _johnaddress extermszip"01730" .
• If a node in a graph needs to be referenced from
  outside this context, a URIref is required.
• Blank nodes make binary relationships out of an
  n-ary one (between John and the street, city,
  etc.).

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????????RDF Schema (RDFS)

• RDFS defines vocabulary for RDF
• Organizes this vocabulary in a typed hierarchy
• Class, subClassOf, type
• Property, subPropertyOf
• domain, range

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4. Other RDF Capabilities

• Containers
• Collections
• Reification
• Structured Values

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???????Key features of an Ontology

• ?????Concept hierarchy,
• ??????concept subsumption

• ??????? InstanceOf Relation (Instances)

• ??????? PartOf Relation (property)

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??????Web Ontology Language (OWL)

• OWL is built on top of RDF
• OWL is for processing information on the web
• OWL was designed to be interpreted by computers
• OWL was not designed for being read by people
• OWL is written in XML
• OWL is a web standard

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OWL Example animals

• lt?xml version"1.0"?gtltrdfRDF
• xmlnsrdf"http//www.w3.org/1999/02/22-rdf-syntax
  -ns"
• xmlnsrdfs"http//www.w3.org/2000/01/rdf-sche
  ma"
• xmlnsowl"http//www.w3.org/2002/07/owl"
• xmlnsdc"http//purl.org/dc/elements/1.1/"
• xmlbase"http//wasp.cs.vu.nl/sekt/ontology/ani
  mal"gt
• ltowlOntology rdfaboutanimal"/gtltowlClass
  rdfID"Eagle"gt
• ltrdfssubClassOfgtltowlClass
  rdfabout"Bird"/gt
• lt/rdfssubClassOfgtlt/owlClassgtltowlClass
  rdfID"Animal"/gt
• ltowlClass rdfID"Fly"gtltowldisjointWithgt
• ltowlClass rdfabout"Penguin"/gtlt/owldisjo
  intWithgt
• ltrdfssubClassOf rdfresource"Animal"/gt
• lt/owlClassgtltowlClass rdfID"Bird"gt
• ltrdfssubClassOf rdfresource"Fly"/gt
• lt/owlClassgt
• ltowlClass rdfID"Penguin"gt
• ltrdfssubClassOf rdfresource"Bird"/gt
• ltowldisjointWith rdfresource"Fly"/gt
• lt/owlClassgt

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DL for OWL SHIQ

• SHIQ ALCQHIR

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SHOIN(D) and OWL-DL

• SHION(D)
• S ALC role transitivity
• H role hiersrchies
• O nominals
• I Inverse roles
• N cardinality restriction
• D datatypes

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OWL2 (OWL1.1)

• New features
• OWL 2 adds new functionality with respect to OWL
  1. Some of the new features are syntactic sugar
  (e.g., disjoint union of classes) while others
  offer new expressivity, including
• keys
• property chains
• richer datatypes, data ranges
• qualified cardinality restrictions
• asymmetric, reflexive, and disjoint
  properties and
• enhanced annotation capabilities

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OWL ???????(I)

• OWL 2 EL ???????????????
• OWL 2 EL enables polynomial time algorithms for
  all the standard reasoning tasks it is
  particularly suitable for applications where very
  large ontologies are needed, and where expressive
  power can be traded for performance guarantees.

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OWL ???????(II)

• OWL 2 QL ???????????????????????
• OWL 2 QL enables conjunctive queries to be
  answered using standard relational database
  technology suitable for applications where
  relatively lightweight ontologies are used to
  organize large numbers of individuals or where it
  is useful or necessary to access the data
  directly via relational queries (e.g., SQL). .

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????Conjunctive Queries

• Conjunctive queries are of the general form (in
  the first order language)

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OWL ???????(III)

• OWL 2 RL ????RDF???????????????
• OWL 2 RL enables the implementation of polynomial
  time reasoning algorithms using rule-extended
  database technologies operating directly on RDF
  triples it is particularly suitable for
  applications where relatively lightweight
  ontologies are used to organize large numbers of
  individuals or where it is useful or necessary to
  operate directly on data in the form of RDF
  triples..

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OWL2?????
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More about OWL2

• ??8?28? ?????
• ????(?????Jeff Z. Pan)OWL2

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More Notations

• F role functionality
• Q qualified cardinality restriction
• R generalised role inclusion
• E existential role restriction

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OWL Variants and DL

• OWL Full is not a DL
• OWL DL SHOIN(D)
• OWL Lite SHIF(D)
• OWL2 Full is not a DL
• OWL2 DL SROIQ(D)
• OWL2 EL EL
• OWL2 QL DL-Lite
• OWL2 RL DLP

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EL

• A lightweight description logic that admits sound
  and complete reasoning in polytime.
• Dropping the (allValusFrom) restriction, whereas
  (someValuesFrom) is retained.
• It should be noted, however, that EL does admit
  (objectPropertyRange), which can be seen as an
  important case of (allValuesFrom).

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EL Syntax and Semantics
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EL Ontologies

• SNOMED CT, the Systematized Nomenclature of
  Medizine, Clinical Terms. SNOMED is a large-scale
  commercial ontology that underlies the
  standardized terminology of the health-care
  systems in the US, the UK, and a couple of other
  countries.
• NCI. The Thesaurus of the National Cancer
  Institute. An ontology that formalizes terms
  related to cancer research.
• The Gene Ontology formalizes terms relating to
  genes and gene products.
• More than 95 of the axioms of the GALEN ontology
  can also be expressed in EL.

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Description Logic Programs (DLP)

• Description Logic Programs is a Horn fragment of
  OWL 2.
• The distinguishing feature of DLP is that it is
  an existential-free fragment that is, while
  reasoning, the universe is fixed in the sense
  that one only needs to consider the objects
  explicitly used in the facts of the ontology.

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Overview of DLP Features

• Essentially, DLP captures RDFS subset of DL --
  plus a bit more.
• RDFS subset of DL permits the following
  statements
• Class C is Subclass of class D.
• Domain of property P is class C.
• Range restriction on property P is class D.
• Property P is Subproperty of property Q.
• a is an instance of class C.
• (a,b) is an instance of property P.

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Overview of DLP Features(continued)

• DLP also captures
• Using the Intersection connective
  (conjunction) in class descriptions
• Stating that a property P is Transitive.
• Stating that a property P is Symmetric.
• DLP can partially capture most other DL
  features.
• Relevant technical issues in LP
• treatment of equality, e.g., uniqueness of
  names.

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DLP and OWL DL

• DLP is able to express the following features of
  OWL DL
• concept disjointness,
• domains and ranges of properties,
• inverse and symmetric properties,
• functional and inverse-functional properties,
• sub-property and equivalence relations
  between object properties,
• transitive properties, and
• a limited form of General Concept Inclusion
  axioms (GCIs).

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DL-Lite

• DL-Lite is a fragment of OWL DL especially
  tailored for handling efficiently large number of
  facts.
• The main focus is to provide efficient query
  answering on the data and to allow the use of
  Relational Database Managment technologies for
  such a purpose.

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DL-Lite

• DL-Lite also includes most of the main features
  of conceptual models, like UML class diagrams and
  ER diagrams. More specifically, DL-Lite includes
  the following features of OWL DL
• a constrained form of someValuesFrom
  restrictions,
• conjunction,
• concept disjointness,
• domains and ranges of properties,
• inverse properties,
• inclusion axioms for object properties.

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Complexity

• The Data Complexity the complexity measured
  with respect to the number of facts in the
  ontology.
• The Taxonomic complexity the complexity
  measured with respect to the size of the axioms
  in the ontology.
• The Query Complexity the complexity measured
  with respect to the number of conjuncts in the
  conjunctive query.
• The Combined Complexity the complexity
  measured with respect to both the size of the
  axioms and the number of facts. In the case of
  conjunctive query answering, the combined
  complexity also includes the query complexity.

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Complexity of Tractable Fragments- OWL DL
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Complexity of Tractable Fragments- OWL Lite
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Complexity of Tractable Fragments- EL
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Complexity of Tractable Fragments- DL-Lite
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Complexity of Tractable Fragments- DLP
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Relationship between the fragments of OWL1.1(OWL2)
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Key Issues of the Semantic Web

• ??,?????
• data, knowledge,and semantics
• ?????, ?????,?????
• Semantic relevance, semantic similarity, and
  semantic distance
• ???????
• Knowledge representation and reasoning
• ????????Scalability
• ???? Approximate reasoning

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??????????DBpedia Mobile

• http//beckr.org/DBpediaMobile/?locationBeijing
• http//beckr.org/DBpediaMobile

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???????HealthFinland Health Information on the
Semantic Web

• http//www.seco.tkk.fi/applications/tervesuomi/
• provide a new kind of solution approach to these
  problems on a national Finnish level. The system
  consists of three main components
• Metadata, ontology, and service infrastructure.
• Semantic content creation process. A content
  creation and harvesting system has been
  implemented for producing semantically annotated
  contents, based on the shared metadata model and
  ontologies.
• Semantic portal HealthFinland (TerveSuomi) and
  its services. The material is published via a
  semantic portal that creates a single national
  entry-point for health information, health
  promotion and health-related news.

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National Semantic Web Ontology Project in Finland
(FinnONTO),

• National Semantic Web Ontology Project in Finland
  (FinnONTO), 2003-2007
• A large national continuation project of
  FinnONTO, called Semantic Web 2.0 (FinnONTO 2.0),
  started in the beginning of 2008.
• The research is directed and is mostly carried
  our by the Semantic Computing Research Group
  (SeCo) at the Helsinki University of Technology
  (TKK) and the University of Helsinki. Also the
  University of Tampere is contributing to the
  work.
• The consortium behind the project included 37
  public organizations and companies funding the
  research during the final year 2007. This
  consortium represents a wide area of functions of
  the society including museums, libraries,
  business, health organizations, government,
  media, and education. Public organizations,
  companies, and universities are participating in
  the project.

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??????????The Dutch Cultural Heritage

• Eculture Project
• STiTCH-Catch
• Chip Project

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Project E-Culture http//e-culture.multimedian.nl
/
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Timeline
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2006????????????
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http//www.ontology-advisory.org/
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??????????????2006?????
Reality SP Reality - VVD
Balkenende Bos Balkenende Bos - Ideal
VVD VVD VVD Verdonk
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Relational Content Analysis
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Example
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???????
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????
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?????

• ??????(Hybrid Logic)?????????? Internal
  Disagrement?

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???

• ?OWL-DL???????
• ???????OWL-DL???????,????????????
• ??OWL-DL??????????????

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?????????
???????????????? ????????????? ??????,?????
????
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Questions and Discussions