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presentation seminar of web ontology language (semantic web)

presentation seminar of web ontology language (semantic web)

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  • For example, in OWL Full we could impose a cardinality constraint on the class of all classes, essentially limiting the number of classes that can be described in any ontology.any legal RDF document is also a legal OWL Full document, and any valid RDF/RDF Schema conclusion is also a valid OWL Full conclusion. an RDF document will in general have to be extended in some ways and restricted in others before it is a legal OWL DL document. Conversely, every legalOWL DL document is still a legal RDF document.
  • OWL became a W3C (World Wide Web Consortium) Recommendation in February 2004.A W3C Recommendation is understood by the industry and the web community as a web standard. A W3C Recommendation is a stable specification developed by a W3C Working Group and reviewed by the W3C Membership.Q. What does the acronym "OWL" stand for?A. Actually, OWL is not a real acronym. The language started out as the "Web Ontology Language" but the Working Group disliked the acronym "WOL." They decided to call it OWL. The Working Group became more comfortable with this decision when one of the members pointed out the following justification for this decision from the noted ontologist A.A. Milne who, in his influential book "Winnie the Pooh" stated of the wise character OWL:"He could spell his own name WOL, and he could spell Tuesday so that you knew it wasn't Wednesday...“See for more: http://www.w3.org/2003/08/owlfaq.html.en

Owl  web ontology language Owl web ontology language Presentation Transcript

  • Seminar
    For
    Web Ontology Language (OWL)
    Prepared by:
    Hussein Ali Ahmad Ghanim
    6/19/20112
    1
    WEB ONTOLOGY LANGUAGE (OWL)
  • Web Ontology Language: OWL
    Web Ontology Language Definition.
    Overview
    Requirements for ontology languages
    OWL Languages
    - OWL, RDF, RDF(s), XML
    References
    6/19/20112
    2
    WEB ONTOLOGY LANGUAGE (OWL)
  • Web Ontology Language
    The Web Ontology Language (OWL) is a family of knowledge representation languages for authoring ontologies.
    The languages are characterised by formal semantics and RDF/XML-based serializations for the Semantic Web.
    Semantic Web led to requirement for a “web ontology language”
    6/19/20112
    3
    WEB ONTOLOGY LANGUAGE (OWL)
  • Overview
    From the overview of OWL1: The OWL Web Ontology Language is designed for use by applications that need to process the content of information instead of just presenting information to humans.
    OWL facilitates greater machine interpretability of Web content than that supported by XML, RDF, and RDF Schema (RDF-S) by providing additional vocabulary along with a formal semantics.
    OWL has three increasingly-expressive sublanguages: OWL Lite, OWL DL, and OWL Full.
    6/19/20112
    4
    WEB ONTOLOGY LANGUAGE (OWL)
  • Lite
    DL
    Full
    Three species of OWL
    Full: uses all the OWL languages primitives. It also allows to combine these primitives in arbitrary ways with RDF and RDF Schema. This includes the possibility to change the meaning of the pre-defined primitives, by applying the language primitives to each other.
    The advantage of OWL Full is that it is fully upward compatible with RDF, both syntactically and semantically.
    The disadvantage of OWL Full is the language has become so powerful as to be undecidable, dashing any hope of complete (let alone efficient) reasoning support.
    DL = Description Logicis a sublanguage of OWL Full which restricts the way in which the constructors from OWL and RDF can be used.
    The advantage of this is that it permits efficient reasoning support.
    The disadvantage is that we loose full compatibility with RDF.
    6/19/20112
    5
    WEB ONTOLOGY LANGUAGE (OWL)
  • Three species of OWL
    Lite:
    - An ever further restriction limits OWL DL to a subset of the language constructors. For example, OWL Lite excludes enumerated classes, disjointness statements and arbitrary cardinality (among others).
    - The advantage of this is a language that is both easier to grasp (for users) and easier to implement (for tool builders).
    - The disadvantage is of course a restricted expressivity.
    6/19/20112
    6
    WEB ONTOLOGY LANGUAGE (OWL)
  • Requirements for ontology languages
    Ontology languages allow users to write explicit, formal conceptualizations of domains models. The main requirements are:
    1. a well-defined syntax
    2. a well-defined semantics
    3. efficient reasoning support
    4. sufficient expressive power
    5. convenience of expression.
    6/19/20112
    7
    WEB ONTOLOGY LANGUAGE (OWL)
  • What is OWL?
    W3C Recommendation, February 2004.
    web standard
    Web Ontology Language
    built on top of RDF
    RDF: the Resource Description Framework is an XML-based language to describe resources.
    for processing information on the web
    designed to be interpreted by computers, not for being read by people
    OWL is written in XML
    6/19/20112
    8
    WEB ONTOLOGY LANGUAGE (OWL)
  • Why OWL?
    OWL is a part of the "Semantic Web Vision" - a future where:
    Web information has exact meaning
    Web information can be processed by computers
    Computers can integrate information from the web
    OWL was designed to
    provide a common way to process the content of web information (instead of displaying it).
    be read by computer applications (instead of humans).
    6/19/20112
    9
    WEB ONTOLOGY LANGUAGE (OWL)
  • OWL
    Inference
    RDF(S)
    Integration
    Integration
    RDF
    Annotation
    XML
    OWL Languages
    • Work on Semantic Web has defined of a collection or “stack” of languages.
    • These languages are then used to support the representation and use of metadata.
    • The languages provide basic machinery that we can use to represent the extra semantic information needed for the Semantic Web
    • XML
    • RDF
    • RDF(S)
    • OWL
    6/19/20112
    10
    WEB ONTOLOGY LANGUAGE (OWL)
  • OWL
    • OWL: the language that is aimed to be the
    standardised and broadly accepted ontology language of the Semantic Web.
    • OWL: is an ontology language designed for the Semantic Web
    • It provides a rich collection of operators for forming concept descriptions
    • It is a W3C standard, promoting interoperation and sharing between applications
    • It has been designed to be compatible with existing web standards
    6/19/20112
    11
    WEB ONTOLOGY LANGUAGE (OWL)
  • The OWL language
    There are different syntactic forms of OWL:
    RDF’s XML-based syntax (primary syntax for OWL)
    an XML-based syntax that does not follow the RDF conventions
    (more easily read by human users) see http://www.w3.org/TR/owl-xmlsyntax/
    an abstract syntax (used in the language specification document) (much more compact and readable) see http://www.w3.org/TR/owl-semantics/
    a graphic syntax based on the conventions of UML
    (an easy way for people to become familiar with OWL)
    6/19/20112
    12
    WEB ONTOLOGY LANGUAGE (OWL)
  • XML provides a surface syntax for structured documents, but imposes no semantic constraints on the meaning of these documents.
    XML Schema is a language for restricting the structure of XML documents and also extends XML with datatypes.
    RDF is a datamodel for objects ("resources") and relations between them, provides a simple semantics for this datamodel, and these datamodels can be represented in an XML syntax.
    RDF Schema is a vocabulary for describing properties and classes of RDF resources, with a semantics for generalization-hierarchies of such properties and classes.
    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.
    6/19/20112
    13
    WEB ONTOLOGY LANGUAGE (OWL)
  • Header
    OWL documents are usually called OWL ontologies, and are RDF documents.
    So the root element of a OWL ontology is an rdf:RDF element which also species a number of namespaces. For example:
    <rdf:RDF
    xmlns:owl="http://www.w3.org/2002/07/owl#"
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf- syntax-ns#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
    xmlns:xsd="http://www.w3.org/2001/XLMSchema#">
    6/19/20112
    14
    WEB ONTOLOGY LANGUAGE (OWL)
  • An OWL ontology may start with a collection of assertions for housekeeping purposes. These assertions are grouped under an owl:Ontologyelement which contains comments, version control and inclusion of other ontologies. For example:
    <owl:Ontologyrdf:about="">
    <rdfs:comment>An example OWL ontology</rdfs:comment>
    <owl:priorVersionrdf:resource="http://www.mydomain.org/uni-ns-old"/>
    <owl:importsrdf:resource="http://www.mydomain.org/persons"/>
    <rdfs:label>University Ontology</rdfs:label>
    </owl:Ontology>
    6/19/20112
    15
    WEB ONTOLOGY LANGUAGE (OWL)
  • XML
    a meta language that allows you to create and format your own document markups
    a method for putting structured data into a text file; these files are
    - easy to read
    - unambiguous
    - extensible
    - platform-independent
    6/19/20112
    16
    WEB ONTOLOGY LANGUAGE (OWL)
  • XML
    a family of technologies:
    - XML 1.0
    - Xlink
    - Xpointer & Xfragments
    - CSS, XSL, XSLT
    - DOM
    - XML Namespaces
    - XML Schemas
    6/19/20112
    17
    WEB ONTOLOGY LANGUAGE (OWL)
  • The pieces
    there are 3 components for XML content:
    - the XML document
    - DTD (Document Type Declaration)
    - XSL (Extensible Stylesheet Language)
    The DTD and XSL do not need to be present in all cases
    6/19/20112
    18
    WEB ONTOLOGY LANGUAGE (OWL)
  • RDF Ontology Language?
    RDF stands for Resource Description Framework
    RDF is a framework for describing resources on the web
    RDF provides a model for data, and a syntax so that independent parties can exchange and use it
    RDF is designed to be read and understood by computers
    RDF is not designed for being displayed to people
    RDF is written in XML
    RDF is a part of the W3C's Semantic Web Activity
    RDF is a W3C Recommendation
    RDFS language features allow for modeling certain semantic aspects of a domain of interest
    6/19/20112
    19
    WEB ONTOLOGY LANGUAGE (OWL)
  • RDF Schema (RDFS)
    is an extension to RDF.
    RDF Schema provides the framework to describe application-specific classes and properties
    Classes in RDF Schema is much like classes in object oriented programming languages. This allows resources to be defined as instances of classes, and subclasses of classes.
    6/19/20112
    20
    WEB ONTOLOGY LANGUAGE (OWL)
  • RDFS Example
    <?xml version="1.0"?>
    <rdf:RDF
    xmlns:rdf= "http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xml:base= "http://www.animals.fake/animals#">
    <rdf:Description rdf:ID="animal">
    <rdf:typerdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
    </rdf:Description>
    <rdf:Descriptionrdf:ID="horse">
    <rdf:typerdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
    <rdfs:subClassOfrdf:resource="#animal"/> </rdf:Description>
    </rdf:RDF>
    6/19/20112
    21
    WEB ONTOLOGY LANGUAGE (OWL)
  • References
    Grigoris Antoniou1 and Frank van Harmelen2(pages 5 - 7) www.csc.liv.ac.uk/~frank/teaching/comp08/lecture6.pdf
    www.w3.org/TR/owl-features/
    www.w3.org/2004/OWL/
    www.csd.abdn.ac.uk/.../OWLTheWebOntologyLanguage/
    static.twoday.net/71desa1bif/files/W3C-OWL-Overview.pdf (pages )
    https://wiki.imise.uni-leipzig.de/Lehre/2005WS/SOntEng/files?get
    W3C Specification: http://www.w3.org/RDF/
    6/19/20112
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    WEB ONTOLOGY LANGUAGE (OWL)