Semantic Web - an introduction

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Semantic Web - an introduction

• By Daniel Wu (danielwujr)

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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
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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
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Semantic?

• Assalamu alaikum
• Lets give it semantic
• Assalamu alaikum is Arabian
• Assalamu alaikum means Hello
• semantikós (Greek) having meaning

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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.)

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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

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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
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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

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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

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SW Features Services (cont.)

• However
• You probably wont see SW
• And this is Weak AI

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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
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SW Knowledge Representation Layers
Semantic Web Layer Cake
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• 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

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

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• 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

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• 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

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• 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.

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Ontology

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

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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.

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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.

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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

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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!

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Ontology Folksonomy

• Can ontology not be hierarchical?
• Can ontology be built from folksonomy?

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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.

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Interoperability between different ontologies
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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

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• 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.

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

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

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SW Layers - Review
Semantic Web Layer Cake
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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
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SW Current Status

• Bump!
• Tools problem
• Ontology problem
• Poor rule engine performance

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SW Current Status

• Important players - Google
• Not taking actions
• Ask question!
• Incompetence
• Competition
• Deception

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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
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Q A

• Welcome!