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Semantic Web - an introduction

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Title: Semantic Web - an introduction


1
Semantic Web - an introduction
  • By Daniel Wu (danielwujr)

2
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
3
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
4
Semantic?
  • Assalamu alaikum
  • Lets give it semantic
  • Assalamu alaikum is Arabian
  • Assalamu alaikum means Hello
  • semantik√≥s (Greek) having meaning

5
Problem Definition
  • Computer have no reliable way to process
    semantics on Web content.
  • (Most of the Webs content today is designed for
    humans to read.)

6
Semantic Web (SW) Proposal
  • Tim Berners-Lee
  • inventor of the WWW
  • 1998
  • Solution
  • Achieving a set of connected applications for
    data on the Web in such a way as to form a
    consistent logical web of data.
  • Develops languages for expressing information in
    a machine-processable form.
  • - Semantic Web Road map, Tim Berners-Lee

7
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
8
SW Features Services
  • Semantic Web
  • The semantic web is an evolving extension of the
    World Wide Web in which web content can be
    expressed not only in natural language, but also
    in a form that can be understood, interpreted and
    used by software agents, thus permitting them to
    find, share and integrate information more
    easily.
  • Source W3C Semantic Web FAQ

9
SW Features Services (cont.)
  • Benefits
  • data integration,
  • whereby data in various locations and various
    formats can be integrated in one, seamless
    application
  • resource discovery and classification (vertical
    search)
  • provide better, domain specific search engine
    capabilities
  • cataloging
  • describing the content and content relationships
    available at a particular Web site, page, or
    digital library
  • intelligent software agents
  • facilitate knowledge sharing and exchange

10
SW Features Services (cont.)
  • However
  • You probably wont see SW
  • And this is Weak AI

11
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
12
SW Knowledge Representation Layers
Semantic Web Layer Cake
13
  • Uniform Resource Identifiers (URI)
  • URI is a name. (a pointer)
  • Uniform Resource Locator (URL) is one form of URI
  • URI does not need to be accessible over the
    Internet

14
  • EXtensible Markup Language (XML)
  • XML provides a surface syntax for structured
    documents
  • XML imposes no semantic constraints on the
    meaning of documents

15
  • Resource Description Framework (RDF)
  • RDF is a simple data model for referring to
    objects ("resources") and how they are related.
  • RDF enable anyone to say anything about anything
  • Triples subject, predicate, object
  • RDF is composed of URIs
  • Ex. Daniel study CS

16
  • RDF schema
  • RDF Schema is a vocabulary for describing
    properties and classes of RDF resources, with a
    semantics for generalization-hierarchies of such
    properties and classes.
  • Ex. Dog SubClassOf Animal

17
  • Web Ontology Language (OWL)
  • OWL adds more vocabulary for describing
    properties and classes among others, relations
    between classes (e.g. disjointness), cardinality
    (e.g. "exactly one"), equality, richer typing of
    properties, characteristics of properties (e.g.
    symmetry), and enumerated classes.

18
Ontology
  • Definition
  • Example
  • Ontology Knowledge presentation
  • Ontology Building ontology
  • Ontology Folksonomy
  • Ontology Interoperability

19
Ontology - Definition
  • (short version)
  • Ontologies are systems of formally defined
    related concepts.
  • (long version)
  • Ontologies define the concepts and relationships
    used to describe and represent an area of
    knowledge. Ontologies are used to classify the
    terms used in a particular application,
    characterize possible relationships, and define
    possible constraints on using those
    relationships.

20
Ontology - Example
  • A company is a type organization.
  • An organization may have a product or a service.
  • An organization is a group of people.
  • An employer may be a person or an organization.
  • A person may be employed by an employer.
  • A person may be in a marriage with only one other
    person at a time.
  • A marriage is a kind of romantic relationship.
  • A friendship is a kind of social relationship.
  • A romantic relationship is a kind of friendship.
  • A person may be socially related to another
    person.
  • A person must have a gender.

21
Ontology Knowledge presentation
  • Back to Assalamu alaikum
  • We need previous knowledge to fully understand
    the concept of Assalamu alaikum
  • previous knowledge
  • world view
  • ontology
  • Oh! Assalamu alaikum means Hello

22
Ontology Building ontology
  • Cyc
  • Top down approach
  • Defines ontology on its own
  • Centralized
  • Semantic Web
  • Bottom up approach
  • Defines language to define ontology
  • Destributed
  • Everyone defines his/her own ontologies!

23
Ontology Folksonomy
  • Can ontology not be hierarchical?
  • Can ontology be built from folksonomy?

24
Interoperability between different ontologies
  • The OWL language can express mappings between
    concepts in different ontologies. But if there
    are many ontologies, and many of them partially
    overlap, it is a non-trivial task to actually
    make the mappings between their concepts.

25
Interoperability between different ontologies
26
Interoperability between different ontologies
  • However Its hard.
  • Having same name doesnt guarantee having same
    meaning
  • A bad example
  • ???????????
  • Wrong conversion
  • Same name doesnt guarantee same meaning

27
  • Web Ontology Language (OWL)
  • OWL adds more vocabulary for describing
    properties and classes among others, relations
    between classes (e.g. disjointness), cardinality
    (e.g. "exactly one"), equality, richer typing of
    properties, characteristics of properties (e.g.
    symmetry), and enumerated classes.

28
  • Logic and Proof
  • Tools to query language for semantic web data
    sources
  • DL (Description Logic), not FOL

29
  • Trust and Digital signature
  • Documents be parsed not just into trees of
    assertions, but into trees of assertions about
    who has signed what assertions.

30
SW Layers - Review
Semantic Web Layer Cake
31
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
32
SW Current Status
  • Bump!
  • Tools problem
  • Ontology problem
  • Poor rule engine performance

33
SW Current Status
  • Important players - Google
  • Not taking actions
  • Ask question!
  • Incompetence
  • Competition
  • Deception

34
Presentation Outline
(Why) Problem Definition
(Who and When) Semantic Web (SW) Proposal
(What) SW Features Services
(How) SW KR Layers
(Where) SW Current Status

knowledge representation
35
Q A
  • Welcome!
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