XML:Managing data exchange

1
XMLManaging data exchange

• Words can have no single fixed meaning. Like
  wayward electrons, they can spin away from their
  initial orbit and enter a wider magnetic field.
  No one owns them or has a proprietary right to
  dictate how they will be used.
• David Lehman, End of the Word, 1991.

2
Central problems of data management

• Capture
• Storage
• Retrieval
• Exchange

3
EDI

• Electronic exchange of standard documents
• In use for some 20 years
• Standards
• ANSI X.12 (US and Canada)
• EDIFACT (International)

4
EDI Advantages

• Paper handling is reduced, saving time and money
• Data can be exchanged in real time
• There are fewer errors since data are keyed only
  once
• Enhanced data sharing enables greater
  coordination of activities between business
  partners
• Money flows are accelerated and payments received
  sooner

5
EDI Adoption

• Much information flow is still on paper
• Electronic exchange is the exception rather than
  the rule
• The Internet is a lower cost solution than EDI
  using value added networks (VANs)

6
SGML

• Document management consumes
• 15 of company revenue
• 25 of labor costs
• 10 - 60 of an office workers time
• Standard generalized markup language (SGML) was
  designed to reduce the cost of document management

7
Markup language

• Embedded information within text about the
  meaning of the text
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  between Miles Davis and Gil Evans has already
  resulted in two extraordinary albumsltcdtitlegtMile
  s Aheadlt/cdtitlegtltcdidgtCL 1041gtlt/cdidgt and
  ltcdtitlegtPorgy and Besslt/cdtitlegt ltcdidgtCL
  1274lt/cdidgt.lt/cdlinergt

8
SGML

• A vendor independent standard for publication of
  all media
• Cross system
• Portable
• Defines the structure of a document
• The parent of HTML and XML

9
SGML Advantages

• Re-use
• Same advantage as with word processing
• Flexibility
• Generate output for multiple media
• Revision
• Version control

10
SGML code

• ltchaptergt
• ltnogt16lt/nogt
• lttitlegtXML Managing Data Exchangelt/titlegt
• ltsectiongt
• ltquotegtltemph type "2"gtWords can have no single
  fixed meaning. Like wayward electrons, they can
  spin away from their initial orbit and enter a
  wider magnetic field. No one owns them or has a
  proprietary right to dictate how they will be
  used.lt/emphgtlt/quotegt
• lt/sectiongt
• lt/chaptergt

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HTML code

• lthtmlgt
• ltbodygt
• lth1gtltbgt16 lt/bgtlt/h1gt
• lth1gtltbgtXML Managing Data Exchangelt/bgtlt/h1gt
• ltpgt
• ltigtWords can have no single fixed meaning. Like
  wayward electrons, they can spin away from their
  initial orbit and enter a wider magnetic field.
  No one owns them or has a proprietary right to
  dictate how they will be used.lt/igt
• lt/pgt
• lt/bodygt
• lt/htmlgt

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The problem with HTML

• Presentation not meaning
• Reader has to infer meaning
• Machines are not very good at inferring meaning

13
XML

• Extensible markup language
• SGML for e- and m-commerce
• A meta-language
• A language to generate languages
• Will steadily replace HTML

14
XML vs. HTML

• Structured text
• User-definable structure
• Context-sensitive retrieval
• Greater hypertext linkage

• Formatted text
• Pre-defined format
• Limited retrieval
• Limited hypertext linking

15
XML rules

• Elements must have both an opening and closing
  tag
• Elements must follow a strict hierarchy with only
  one root element
• Elements may not overlap other elements
• Element names must obey XML naming conventions
• XML is case sensitive

16
HTML vs. XML
17
Processing shift

• From server to browser
• Browser can read meaning of the data
• Less data transmitted

18
Searching

• Search engines look for appropriate tags in the
  XML code
• Faster
• More precise

19
Expected gains

• Store once and format many times
• Hardware and software independence
• Capture once and exchange many times
• Accelerated targeted searching
• Less network congestion

20
XML language design

• Designers must define
• Allowable tags
• Rules for nesting tags
• Which tagged elements can be processed

21
DTD

• Document type definition
• An XML file
• Informs application how to interpret tags
• Not required, but a good idea
• XML can process well-formed XML documents

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DTD

• The DTD defines
• The names and contents of all elements that are
  permissible in a certain document
• How often an element may appear
• The order in which the elements must appear
• Whether the start- or end-tag may be omitted
• The contents of all elements
• The attributes and their default values
• The names of the reference symbols that may be
  used

23
DOM

• Document object model
• The data model for an XML document
• A tree (1m)

24
DTD (cdlib.dtd)

• lt!--DTD for CD library--gt
• lt!ELEMENT cdlibrary (cd )gt
• lt!ELEMENT cd (cdid , cdlabel , cdtitle , cdyear
  , track )gt
• lt!ELEMENT cdid (PCDATA )gt
• lt!ELEMENT cdlabel (PCDATA )gt
• lt!ELEMENT cdtitle (PCDATA )gt
• lt!ELEMENT cdyear (PCDATA )gt
• lt!ELEMENT track (trknum, trktitle, trklen)gt
• lt!ELEMENT trknum (PCDATA )gt
• lt!ELEMENT trktitle (PCDATA )gt
• lt!ELEMENT trklen (PCDATA )gt

25
DOM schema(XML Authority representation)
26
XML (cd.xml)

• lt?xml version "1.0"?gt
• lt!DOCTYPE cdlibrary SYSTEM "cdlib.dtd"gt
• ltcdlibrarygt
• ltcdgt
• ltcdidgtA2 1325lt/cdidgt
• ltcdlabelgtAtlanticlt/cdlabelgt
• ltcdtitlegtPyramidlt/cdtitlegt
• ltcdyeargt1960lt/cdyeargt
• lttrackgt
• lttrknumgt1lt/trknumgt
• lttrktitlegtVendomelt/trktitlegt
• lttrklengt230lt/trklengt
• lt/trackgt
• lt/cdgt
• lt/cdlibrarygt

27
XSL

• Extensible stylesheet language
• Defines how an XML document is rendered
• An XML file

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XSL

• Results of applying cd.xsl

29
cd.xsl

• lt?xml version"1.0"?gt
• ltxslstylesheet xmlnsxsl"http//www.w3.org/TR/WD
  -xsl"gt
• ltxsltemplate match"/"gt
• lthtmlgt
• lttitlegtComplete List of Songslt/titlegt
• ltbodygt
• lttable border"2"gt
• lttr bgcolor"khaki"gt
• ltth align"left"gtCD idlt/thgt
• ltth align"left"gtTitlelt/thgt
• ltth align"left"gtLabellt/thgt
• ltth align"left"gtYearlt/thgt
• lt/trgt
• lttrgt
• lttd align"left"gtltxslvalue-of
  select"//cdid"/gtlt/tdgt
• lttd align"left"gtltxslvalue-of
  select"//cdtitle"/gtlt/tdgt
• lttd align"left"gtltxslvalue-of
  select"//cdlabel"/gtgtlt/tdgt
• lttd align"left"gtltxslvalue-of
  select"//cdyear"/gtlt/tdgt
• lt/trgt

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Converting XML

• Transformation and manipulation
• XSLT
• One XML vocabulary to another
• FPML to finML
• Re-ordering, filtering, and sorting
• Rendering
• XSLT
• e.g., XML to WAP

31
XML and databases

• XML is a data management tool
• XML documents will have to be stored for the
  long-term
• Need a DBMS

32
DBMS requirements

• Store a large number of documents
• Store large documents
• Support access to portions of a document (e.g.,
  the data for single CD in a library of 20,000
  CDs)
• Concurrent access
• Version control
• Integrate data from other sources

33
RDBMS

• Document-centric
• Store as CLOB
• Data-centric
• Object-relational extensions to support element
  retrieval and update
• Expect RDBMS vendors to offer extensions to
  support XML

34
Database to XML

• A significant proportion of Web pages are
  generated from databases
• Instead of converting to HTML these should be
  converted to XML
• Render with XSL
• Need tools for converting relational data to XML

35
OODBMS

• A good fit to the DOM
• Little development at this stage
• Vendors have fewer resources

36
XML database

• Special purpose XML database
• Tamino
• This is a new area and you will need to monitor
  developments

37
Conclusion

• XML is a significant technological development
• Its main purpose is to support data exchange
• It will lower the cost of business transactions
• It will be an critical data management technology