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What is XML (and RDF)?

What is XML (and RDF)?. John McCarthy & Frank Olken jlmccarthy@lbl.gov olken@lbl.gov Lawrence Berkeley National Laboratory Roy Tennant rtennant@library.berkeley.edu The Library, University of California, Berkeley. http://www.lbl.gov/~olken/epa.html Metadata Registries Workshop II

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What is XML (and RDF)?

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  1. What is XML (and RDF)? John McCarthy & Frank Olken jlmccarthy@lbl.govolken@lbl.gov Lawrence Berkeley National Laboratory Roy Tennant rtennant@library.berkeley.edu The Library, University of California, Berkeley http://www.lbl.gov/~olken/epa.html Metadata Registries Workshop II Washington, DC 15 April 1998

  2. XML: Extensible Markup Language • World Wide Web Consortium (W3C) Recommendation, Version 1.0 February 1998 • Simplified SGML (Standard Generalized Markup Language, ISO 1986) • adopts UNICODE international character set • Next generation HTML: • semantic structure of document or data • extensible, industry-specific tag sets • display determined by stylesheets (CSS, XSL)

  3. A Simple XML Example <?xml version=“1.0”?> <book> <author> <name>Richard Light</name> <email>rlight@somewhere.com</email> </author> <title>Presenting XML</title> </book> Markup Character Data

  4. Goals & Philosophy of XML • Overcomes shortcomings of HTML: • allows processing of Web documents by sophisticated document processing software • Overcomes shortcomings of SGML: • allows media-independent electronic publishing • Interoperates with SGML and HTML • Provides vendor-neutral data exchange

  5. XML History • Roots in SGML • very extensible but very complicated • a simplified SGML could greatly expand the power and flexibility of the Web • XML proposal to W3C in July 1996 • John Bosak, Sun Microsystems, now XML Chair • First XML Meeting, August 1996, Seattle

  6. XML Family of Standards • XML (W3C Proposal, Version 1.0 February 1998) • simplified SGML (ISO 8879:1986) • Extensible Stylesheet Language (XSL) • based on DSSSL (stylesheet specification ISO/IEC 10179, used for SGML) • XML Linking Language (XLink) • based on HyTime (ISO/IEC 10744:1992) • provides rich linking mechanisms (e.g., multidirectional links)

  7. What is W3C? • World Wide Web Consortium (www.w3.org) • Tim Berners-Lee, Director • Staff at MIT, US; INRIA, France; Keio Univ., Japan • Over 220 member organizations (April 1998) • for profit > $50,000,000 pay $50,000/year • other for profit, gov’t, and non profit pay $5,000/year • Fast track Web standards development • Short-term, specific focus Working Groups

  8. Current W3C Development Areas • Architecture • HTTP-NG, etc. • User Interface • HTML, CSS, XSL, etc. • Privacy and Site Rating • P3P, PICS, etc. • Data Exchange • XML, RDF, etc.

  9. XML Bandwagon • Major support from vendors: • Microsoft, Sun, Netscape, ... • High-end technical publishers (SGML) • Conferences: • SGML/XML, November 1997, Wash. DC • XML Conference, March 1998, Seattle • SGML/XML, May 1998, Paris • XML World, September 1998, Ottawa • Books, Software, Web sites, Articles

  10. XML Software Tools • XML-enabled Web browsers • e.g., Microsoft Internet Explorer, Netscape • XML parsers • e.g., http://www.microsoft.com/xml/ • XML stylesheet editing software • e.g., http://www.arbortext.com/xmlstyler/ • CDF (Channel Definition Framework) • e.g., http://www.microsoft.com/standards/cdf.htm • Software for structured text • Survey: http://www.cs.uku.fi/~kuikka/systems.html • Pointers: http://www.sil.org/sgml/publicSW.html • SoftQuad (www.sq.com), Arbortext (www.arbortext.com)

  11. Discipline-Specific Proposals • Chemical Markup Language (ChemML) • Math Markup Language (MathML) • Electronic Document Interchange (XML-EDI) • Bioinformatic Sequence Markup Language (BSML) • Synchronized Multimedia Integration Language (SMIL) • Web Interface Definition Language (WIDL) • Precision Graphics Markup Language (PGML) • Information and Content Exchange (ICE) • Tutorial Markup Language (TML) • Open Software Description Format (OSD)

  12. XML and EDI • XML-EDI Group within Graphic Communications Association • XML-EDI being examined in X12 • CommerceNet Industry Initiative • creating tag sets for EDI • Telecommunications Interchange Markup (TCIF/IPI) • More information: • http://www.xmledi.org/ (http://www.geocities.com/WallStreet/Floor/5815/)

  13. General Proposals • W3C Document Object Model (DOM) • enables script access to document components • Channel Definition Format (CDF) • specifications for push content • XML-Data (Note from Microsoft) • XML encoding for DTDs and data types • Resource Description Framework (RDF) • metamodel for Web metadata

  14. Resource Description Framework • Interoperability for applications that use metadata • Enables industry-specific groups to independently define, maintain, and reuse vocabularies (schemas) • Architecture includes: • Graph data model (like NIAM, AI frames) • Transfer syntax (XML) for interchange • Human-readable and machine-parseable syntax • RDF Working Groups (http://www.w3.org/RDF/) • model and syntax • schema

  15. RDF Architecture XML replaces SGML and allows the expression of structure; RDF allows the expression of semantics. - Tim Berners-Lee

  16. XML, Metadata & Registries • Encode metadata in XML (and RDF) • Use Registries to manage tag sets • For self-describing data and metadata exchange (transmission format) • Links to reference metadata registries • Use XML/RDF for registry schemas (metamodels)

  17. W3C Namespaces Proposals • Naming Contexts (e.g., ISO 11179) • Divide and conquer name collisions • Library of Congress <title> means book title: <?xml:namespace ns=“http://www.loc.gov/” prefix=“LC”> <LC:title>From Here to Eternity</LC:title> • Department of Commerce <title> means job title: <?xml:namespace ns=“http://www.doc.gov/” prefix=“C”> <C:title>Chief Bottle Washer</C:title> • W3X document on XML Namespaces • http://www.w3.org/TR/WD-xml-names

  18. Mixing & Matching Namespaces <?xml:namespace ns=“http://books.org/” prefix=“B”?> <?xml:namespace ns=“http://ecommerc.org/” prefix=“E”?> <E:Order> <E:SoldTo> <E:LastName>Layman</E:LastName> <E:FirstName>Andrew</E:FirstName> </E:SoldTo> </E:Order> <E:Item Price=“5.95”> <B:Book> <B:Title>The Call of the Wild</B:Title> <B:Author>London, Jack</B:Author> </B:Book> </E:Item>

  19. Where XML is Going • Increasing industry interest and acceptance • Parsers in multiple computer languages: • Java, C++, Perl, Python, etc. • Additional industry-specific tag sets • Full Web browser support • Growing set of authoring/processing tools

  20. XML Resources • Standards proposals: http://www.w3.org/XML/ • Web Sites: • Robin Cover: http://www.sil.org/sgml/xml.html • Seybold/O’Reilly: http://xml.com/ • Web Review: http://webreview.com/xml/ • Electronic Discussions: • XML-L: LISTSERV@listserv.hea.ie • XML-Dev: http://www.lists.ic.ac.uk/hypermail/xml-dev/ • Documents: • FAQ: http://www.ucc.ie/xml/ • BYTE article: http://www.byte.com/art/9803/sec5/sec5.htm

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