Comp3503 XML and Ontologies

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Comp3503XML and Ontologies

• Daniel L. Silver, Ph.D.

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Outline

• XML Fundamentals
• XML Use
• Ontology Fundamentals
• Application of Ontologies
• Ontologies and the Semantic Web

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Problems with the HTML based Web

• HTML documents focus on display and not structure
  and meaning of data - an information maze devoid
  of meaning
• Inefficient use of tags - every instance of data
  must be tagged for presentation
• Fixed number of tags - can not be extended (not
  extensible)
• Confusing mix of standards (Netscape and IE
  innovations)
• HTML search is based on keywords without context
• Client-server applications cannot easily exchange
  data using HTML

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HTML focuses on display syntax

• HTML tags such as ltBgtSimpsonlt\Bgt tell how to
  display the word Simpson
• Focus is on presentation (format, syntax)
• But its does not define what Simpson means
• A persons name? A city? A company?
• Or its structural relationship to other data
• Full name? Last name? First name?

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The XML idea

• eXtensible Markup Language
• XML defines meaning (semantics)
  ltlnamegtSimpsonlt\lnamegt
• In terms of structural relationships
• Independent of presentation

ltmail_adrsgt ltfnamegtHomerlt\fnamegt
ltlnamegtSimpsonlt\lnamegt ltstrnumgt1234lt\strnumgt
ltstrgtHickup Lanelt\strgt lt\mail_adrsgt
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What is XML?

• 1996 - A simplified form of SGML for the web
  (Standardized General Markup Language)
• Both machine and human readable
• Separates content, structure and presentation
• Extensible -users can define structure and
  meaning
• Supports information reuse and processing
  autonomy (application decides how to use/present)

SGML
HTML
XML
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The W3Cs 10 Design Requirements for XML

• XML shall be easily usable over the Internet.
• XML shall support a wide variety of applications.
• XML shall be compatible with SGML.
• It shall be easy to write programs that process
  XML documents.
• The number of optional features in XML is to be
  kept to the absolute minimum, ideally zero.
• XML documents should be human-legible (easy to
  understand).
• The design of XML had to be done quickly
• The design of XML shall be exact (formal) and
  concise to easy processing of the code.
• XML documents should be easy to create.
• Terseness (brevity) in XML markup is of minimal
  importance.

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XML Fundamentals
lt?xml version "1.0"?gt ltcontactsgt
ltcontactgt ltLastNamegtBlacklt/LastNamegt
ltFirstNamegtJohnlt/FirstNamegt lt/contactgt
lt/contactsgt
lt!ELEMENT contacts (contact) gt lt!ELEMENT contact
(LastName, FirstName) gt lt!ELEMENT LastName
(PCDATA) gt lt!ELEMENT FirstName (PCDATA) gt
DTD Structure
Presentation in Context
XML Content
XSL Presentation
lt?xml version"1.0"?gt ltxslstylesheet xmlnsxsl
"http//www.w3.org/TR/WD-xsl"gt
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XMLs Intended Use

• Standard format for exchanging data
• Promote cross-platform and cross-application
  schema independent of data content, use and
  presentation
• Oriented toward giving meaning to data, and does
  not emphasize display issues
• Client describes valid data for display
• Server describes valid data for exchange

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XMLs Intended Use

• Allows organizations to maintain proprietary
  databases while at the same time communicate
  information with one another
• Schemas for specific domains have been created
• Music (MusicXML example)
• Chemical symbols (CML)
• Mathematical formulas (MathML)
• Common industry models (EDI for B2B)
• Web resource descriptions (directories,
  addresses)

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XML versus HTML

• XML is not a replacement for HTML
• XML and HTML were designed with different goals
• HTML was designed to display data and to focus on
  how data looks
• XML was designed to describe data and to focus on
  what data means
• They complement each other

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XML eXtensibility

• XML allows you to create your own definitions of
  data and there relationship to other pieces of
  data
• Thus the name
• eXtensible
• Note that XML is case sensitive

lt?xml version"1.0"?gt ltPeoplegt ltPersongt
ltNamegt ltFirstgtPatricklt/Firstgt
ltLastgtJoelt/Lastgt lt/Namegt lt/Persongt lt/Peoplegt
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Using IE to Explore XML

• You can use Internet Explorer to view an XML
  document directly
• A plus () or minus sign (-) to the left of the
  XML elements can be clicked to expand or collapse
  the element structure
• Or view the raw XML source using "View Source"
  from the browser menu
• Example cd_catalog.xml

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Defining XML Structure

• DTD Document Type Definition defines the fields
  in an XML document and their relation to one
  another (schema)
• Meta-data data about data
• Can be included in .xml file or referenced as
  a .dtd file
• Used by applications to validate XML data

lt!ELMENT People (Person) gt lt!ELMENT Person
(Name) gt lt!ELMENT Name (First, Last) gt lt!ELMENT
First (PCDATA) gt lt!ELMENT Last (PCDATA) gt
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Processing an XML Document
lt?xml version"1.0"?gt ltPeoplegt ltPersongt
ltNamegt ltFirstgtPatricklt/Firstgt
ltLastgtJoelt/Lastgt lt/Namegt lt/Persongt lt/Peoplegt
XML Content

• An application that wishes to use XML
• data should parse the data using a DTD.
• There are two approaches
• DOM read the entire document using the
• DTD and build a tree of elements
• SAX parse on demand (interactively)
• as each new element is encountered

DOM Document Object Model SAX Simple API
for XML
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Processing an XML Document

• Internet Explorer 5.0 () has a built in
  DOM-based XML parser, msxml
• DTD can be embedded in XML or referenced
• Examples
• simple_example.xml with DTD embedded
• letter.xml and letter.dtd

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Displaying XML Documents

• Can be accomplished in various ways, any program
  that can parse the XML can display the
  information
• Here is a simple HTML solution
• simple_contact.html - XML is embedded, DTD is not
  required
• Javascript could be used instead
• article.xml and DOMexample.html
• note.xml and note.html

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Displaying XML Documents

• An XSL eXtensible Stylesheet Layout can be used
• Examples
• Basic - contact3.xml using contact_list3.xsl
• Full function contact.xml using
  contact_list.xsl
• Handheld contact2.xml using contact_list2.xsl

lt?xml version"1.0"?gt ltxslstylesheet xmlnsxsl
"http//www.w3.org/TR/WD-xsl"gt
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Transferring Data with XML

• It is possible to use XML as a method of
  transferring meaningful data between applications
  even when application databases do not match
• Adherence to XML DTD is the key

ODBC
JDBC
XML
App A
App B
DB2
Oracle
Common DTD
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Smart Searches on the Internet

• With XML and DTDs, keyword searches on the
  Internet can now be aimed at the appropriate
  systems, databases, pages
• A syntactic search using IE
• cook New York kitchen restaurant
• would become
• A semantic search
• ltoccupationgtcooklt/occupationgt
• ltcitygtNew Yorklt/citygt

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VXML

• Voice XML - vxml
• Sound embedded as content and processed as per
  style sheet
• Other media types will be used as well
• W3C references
• vxml examples

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General XML References

• http//www.w3.org/XML/
• http//www.xmlfiles.com/xml/
• http//xml.sys-con.com/

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What is an Ontology?

• A specification of a conceptualization
• Example
• An Author is a person
• An Author writes text, books, poems, stories
• A book may have two Authors
• A well understood semantic schema
• A description of the concepts and relationships
  that exist for an agent or community of agents
• A set of terms describing the application domain
• A set of definitions of formal vocabulary for
  communication between agents

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What is an Ontology used for?

• To enable information and knowledge sharing and
  reuse between different applications
• Useful for human understanding and interaction
• An XML DTD is a primitive form of ontology but
  lacks the ability to capture complex
  relationships between terms
• Good first link on Ontologies http//www.aaai.org
  /AITopics/html/ontol.html

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Ontology use in Artificial Intelligence

• Originally designed for use in AI
• Uses in the AI field
• Knowledge Engineering
• Natural Language Processing
• Intelligent Information Integration
• Popularized during the movement to create XML and
  the use of XML by Intelligent Agents of the
  Semantic Web

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A Great Introduction to

• XML, Ontologies, and the Semantic Web

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Applications of Ontologies

• Knowledge Engineering
• Semantic Web share/exchange of knowledge
• Semi-structured Data web pages
• Ontology-based Information Systems Geographic
  IS, Legal IS, Business IS
• Ontologies Machine Learning / Knowledge
  Discovery
• E-Business / E-Commerce

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Application to Knowledge Management

• Efficient knowledge management has been
  identified as key to maintaining the
  competitiveness of organizations.
• Ontologies have been developed in the knowledge
  engineering discipline as a means to share and
  reuse knowledge
• Has been used in large company-wide networks,
  call centers, B2C and B2B E-Commerce

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Whats AheadTechnology, Software, Languages

• Ontologies and XML
• Ontology Exchange Language (XOL)
• Technologies
• KQML(Knowledge Query and Manipulation Language)

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Ontologies and XML

• XML is emerging as the standard language for data
  interchange on the web
• Desirable to exchange ontologies using XML syntax
• Has led to development of XML based languages,
  defining a language on top of XML

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Ontologies and XML

• XML Based Languages
• SHOE
• Ontology Exchange Language (XOL)
• Ontology Markup Language (OML)
• Resource Description Framework Schema Language
  (RDFS)
• Riboweb
• OIL (Ontology Interface Layer) - extention of
  RFDS

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Ontology Exchange Language (XOL)

• Language for the exchange of ontologies, created
  to facilitate the creation of shared ontologies
• Example can be applied to databases to make
  information sharing easier

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Technologies

• Ontology Editors
• - the creation of joint ontologies for a number
  of agents is challenging
• - distributed development of ontologies needs
  tools for synchronizing
• - Examples Protégé
• Webonto
• OILed

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Technologies

• MetaData Editors
• - ontologies can also be used along with meta
  data
• - ontology aware metadata tools simplify the
  creation of metadata for web resources
• - Reggie MetaData Editor - an example of a
  simple java based editor

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KQML (Knowledge Query and Manipulation Language)

• Language and protocol for exchanging information
  and knowledge
• Both a message format and message-handling
  protocol to support run-time knowledge sharing
  among agents
• Uses
• As a language for an application program to
  interact with an intelligent system
• For two or more intelligent systems to share
  knowledge

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KQML (Knowledge Query and Manipulation Language)

• Provides a basic architecture for knowledge
  sharing through a special class of agent called
  communication facilitators which coordinate the
  interactions of other agents
• Being used in concurrent engineering, intelligent
  design and intelligent planning and scheduling

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OIL(Ontology Interface Layer)

• Ontologies will play a major role in supporting
  information exchange
• A prerequisite for this role is the development
  of a joint standard for specifying and exchanging
  ontologies
• The Ontology Interface Layer protocol is a
  proposal for such a standard
• Proposal for web-based representation and
  inference layer for ontologies
• What OIL is trying to achieve - to ensure a Web
  where information can be understood by machines
  as well as by humans

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Ontologies Step by Step

• http//www.cs.umd.edu/users/hendler/sciam/walkthru
  .html

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Ontologies and The Semantic Web

• The next evolutionary step for the Web is the
  Semantic Web
• Idea of WWW inventor Tim Berners-Lee
• The semantic web is a mesh of information linked
  so it is easily processed by machines
• Will allow meaningful exchange of information and
  reasoning on the World Wide Web
• Resource Description Framework (RDF)
  http//www.xml.com/pub/a/2001/01/24/rdf.html

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Ontologies and The Semantic Web

• Ontologies that will allow machines to easily
  understand each other
• Software agents will be able to understand and
  work with the words and info humans use in
  emails, documents and databases
• Ontologies and the semantic web will make
  searching for things on the web much easier
• Will automate many time consuming low-level
  tasks, for example

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Summary

• An ontology is basically a formal specification
  to enable communication between agents
• Used for knowledge sharing among computers and
  people
• Ontologies are a core component behind the
  Semantic Web which is the future of the Internet

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References

• http//www.aaai.org/AITopics/html/ontol.html
• http//www-ksl.stanford.edu/kst/what-is-an-ontolog
  y.html
• http//www.cs.umd.edu/users/hendler/sciam/walkthru
  .html
• http//ecommerce.ncsu.edu/technology/topic_XML.htm
  l
• http//ksl-web.stanford.edu/kst/ontology-sources.h
  tml
• http//www.cs.umbc.edu/kqml/

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THE ENDdanny.silver_at_acadiau.ca