Markup Languages and the Semantic Web

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Markup Languages and the Semantic Web

• Lecture Notes Prepared by
• Jagdish S. Gangolly
• Interdisciplinary Ph.D Program in Information
  Science
• State University of New York at Albany

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Markup Languages

• Knowledge assumed
• HTML
• DTD (Document Type Definition)
• Tags
• Format (confusion between format and other tags)
• Structure (Too flexible, and so almost useless)
• Content (virtually none)
• Very poor in semantics
• Inability to exploit latent semantics
• Users at the mercy of browsers
• Inflexibility in adding new tags un less blessed
  by browsers

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XML I

• SGML, the forerunner of HTML
• Too complex (annotated SGML standard runs over
  1,000 pages
• Too flexible
• Little browser support
• XML
• Less complex and yet extensible
• Flexible in expressing semantics
• Browser support

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XML II

• Separation of format, content, and structure tags
• Content Schema
• Rich set of data types
• Easy to understand and implement
• Format XSL (XML Style-sheet language)
• Complex and no universal browser support
• Such support may not be crucial because of XSLT
  (XSL Transform) which enables HTMLize XML
• Structure Subsumed in content and format
• Representing richer semantics than HTML allowed

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XML III

• Discipline enforced
• Document Type Definition, required to specify the
  grammar of HTML and SGML required programmers to
  be familiar with one more language (EBNF -
  Extended Backus-Naur Formalism) in which DTDS are
  represented.
• Good browser support
• DOM (Document Object Model), SAX (Simple API for
  XML), and Namespaces facilitates machines to
  communicate and (understand) mutual data to an
  extent

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Semantic Web

• ..is a mesh of information linked up in such a
  way as to be easily processable by machines, on a
  global scale. (http//infomesh.net/2001/swintro/)

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Motivation

• Need for interchangeability of information
  (information sharing)
• Need for interchangeability, translatability,
  uniformity of ontologies
• Need for improving precision in retrieval
• Need for web services based on understanding of
  data as well as metadata

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Semantic Web Components

• Data
• Structure
• Content
• Format
• Ontology
• Metadata
• Representation Languages
• Facility for metadata Interchange

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Data

• Data (Semi-structured as well as structured)
• Structure Tags XML-Schema
• Content Tags XML-Schema
• Ontology Ontology representation languages

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Metadata I

• Representation languages based on First Order
  Logic
• KIF-based Ontolingua (http//www.ksl.stanford.edu/
  software/ontolingua/
• Loom (http//www.isi.edu/isd/LOOM/LOOM-HOME.html)
• Frame-Logic (http//www.cs.sunysb.edu/kifer/dood/
  papers.html)

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Metadata II

• Languages using standardised syntax
• Simple HTML Ontology Extensions (SHOE)
  (http//www.cs.umd.edu/projects/plus/SHOE/)
• XOL Ontology Exchange Language (XOL)(http//www.ai
  .sri.com/pkarp/xol/)
• Ontology Markup Language (OML and CKML) (Ontology
  Markup Language (OML and CKML)
• Resource Description Framework Schema Language
  (RDFS) (http//www.w3.org/TR/rdf-schema/)
• RiboWEB (http//www-smi.stanford.edu/projects/heli
  x/riboweb/kb-pub.html)

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Metadata III

• OIL (Ontology Interchange Language)
  (http//www.ontoknowledge.org/oil/)
• DAMLOIL (http//www.daml.org)
• XFMLCAMEL (eXchangeable Faceted Metadata
  Language Compound term composition
  Algebraically-Motivated Expression Language)
  (http//www.csi.forth.gr/tzitzik/XFMLCAMEL/)
• Good sources of information
• http//www.cs.umd.edu/users/hendler/sciam/walkthru
  .html
• http//www.w3.org/2001/sw/

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Dublin Core

• Metadata Elements?ISO 158362003

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RDF (http//www.xml.com/pub/a/2002/01/30/daml1.ht
ml)

• XML based language that allows you to define
  classes and properties
• Product/rdfslabel An item sold by Super
  Sports Inc.
• 
  Product Number
  
  
  1/rdf-schemaLiteral"/

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RDF

• "there is a Person identified by
  http//www.w3.org/People/EM/contactme, whose
  name is Eric Miller, whose email address is
  em_at_w3.org, and whose title is Dr."

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RDF
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RDF

• df-syntax-ns"
• xmlnscontact"http//www.w3.org/2000
  /10/swap/pim/contact"
• ple/EM/contactme"
• Eric Millere
• g"/
• Dr.tle

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DAMLOIL I (http//www.xml.com/pub/a/2002/01/30/da
ml1.html)

• DAMLOIL also allows you to define instances of
  classes and specify their properties
• Water
  Bottle 38267umber
• DAMLOIL allows datatyping
• 
  Product Number
  
  0/XMLSchemanonNegativeInteger"/
  

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DAMLOIL II

• Provides for uniqueness, equivalence,
  enumerations, disjoint classes, disjoint unions
  of classes, non-exclusive Boolean combinations of
  classes, intersection of classes, sub-classing,
  property restrictions
• Rich enough to model ontologies

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Semantic Web Stack of Expressive Power
(Berners-Lee)
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Semantic Web Stack of Expressive Power
(Berners-Lee)

• URI (Uniform Resource Identifier)
• http//www.ietf.org/rfc/rfc2396.txt
• Unicode
• unicode.org
• XML
• http//www.w3.org/XML/
• RDF
• http//www.w3.org/RDF/
• RDF-S (RDF Schema)
• www.w3.org/TR/2000/CR-rdf-schema-20000327/
• SPARQL
• www.w3.org/TR/rdf-sparql-query/

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• OWL (Web Ontology Language)
• http//www.w3.org/2004/OWL/
• RIF
• http//www.w3.org/TR/rif-core/
• Unifying Logic
• Proof
• Crypto
• Trust

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Web Ontology Language (OWL) I

• OWL Lite supports those users primarily needing a
  classification hierarchy and simple constraints.
• OWL DL supports those users who want the maximum
  expressiveness while retaining computational
  completeness (all conclusions are guaranteed to
  be computed) and decidability (all computations
  will finish in finite time).
• OWL Full is meant for users who want maximum
  expressiveness and the syntactic freedom of RDF
  with no computational guarantees.
• Source http//www.w3.org/TR/owl-features/

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Semantic Web Readings

• Semantic Web Readings
• The Semantic Web In Breadth, by Aaron Swartz
• http//logicerror.com/semanticWeb-long
• The Semantic Web An Introduction
• http//infomesh.net/2001/swintro/