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
• ltcdlinergtThis uniquely creative collaboration
  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

11
HTML code

• lthtmlgt
• ltbodygt
• lth1gtltbgt16lt/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

12
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
XML Schema

• The schema defines
• The names and contents of all elements that are
  permissible in a certain document
• The structure of the document
• How often an element might appear
• The order in which the elements must appear
• The type of data the element contains

22
DOM

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

23
Schema (cdlib.xsd)

• XML declaration and root of all schema documents
• lt?xml version"1.0" encoding"UTF-8"?gt
• ltxsdschema xmlnsxsd'http//www.w3.org/2001/XMLS
  chema'gt

24
Schema (cdlib.xsd)

• CD library definition
• ltxsdelement name"cdlibrary"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement name"cd" type"cdType
• minOccurs"1 maxOccurs"unbounded"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt
• lt/xsdelementgt

25
Schema (cdlib.xsd)

• CD definition
• ltxsdcomplexType name"cdType"gt
• ltxsdsequencegt
• ltxsdelement name"cdid" type"xsdstring"/gt
• ltxsdelement name"cdlabel" type"xsdstring"/gt
• ltxsdelement name"cdtitle" type"xsdstring"/gt
• ltxsdelement name"cdyear" type"xsdinteger"/gt
• ltxsdelement name"track" type"trackType"
  minOccurs"1"
• maxOccurs"unbounded"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt

26
Schema (cdlib.xsd)

• Track definition
• ltxsdcomplexType name"trackType"gt
• ltxsdsequencegt
• ltxsdelement name"trknum" type"xsdinteger"/gt
• ltxsdelement name"trktitle" type"xsdstring"/gt
  
• ltxsdelement name"trklen" type"xsdtime"/gt
• lt/xsdsequencegt
• lt/xsdcomplexTypegt

27
Common datatypes

• string
• boolean
• uriReference
• decimal
• float
• integer
• time
• date

28
XML (cd.xml)

• lt?xml version "1.0 encodingUTF-8?gt
• ltcdlibrary xmlnsxsi"http//www.w3.org/2001/XMLSc
  hema-instance"
• xsinoNamespaceSchemaLocation"cdlib.xsd"gt
• ltcdgt
• ltcdidgtA2 1325lt/cdidgt
• ltcdlabelgtAtlanticlt/cdlabelgt
• ltcdtitlegtPyramidlt/cdtitlegt
• ltcdyeargt1960lt/cdyeargt
• lttrackgt
• lttrknumgt1lt/trknumgt
• lttrktitlegtVendomelt/trktitlegt
• lttrklengt230lt/trklengt
• lt/trackgt
• lt/cdgt
• lt/cdlibrarygt

29
XSL

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

30
XSL

• Results of applying cd.xsl
• Pyramid, Atlantic, 1960 A2 1325
• 1 Vendome 000230
• 2 Pyramid 001046
• Ella Fitzgerald, Verve, 2000 D136705
• 1 A tisket, a tasket 000237
• 2 Vote for Mr. Rhythm 000225
• 3 Betcha nickel 000252

31

• lt?xml version"1.0" encoding"UTF-8?gt
• ltxslstylesheet xmlnsxsl"http//www.w3.org/1999/
  XSL/Transform"gt
• ltxsloutput encoding"UTF-8" indent"yes"
  method"html" version"1.0" /gt
• ltxsltemplate match"/"gt
• lthtmlgt
• ltheadgt
• lttitlegtComplete List of Songslt/titlegt
• lt/headgt
• ltbodygt
• lth2gtComplete List of Songslt/h2gt
• ltxslapply-templates select "cdlibrary" /gt
• ltxslfor-each select"cd"gt
• ltfont color"maroon"gt
• ltxslvalue-of select"cdtitle" /gt ,
• ltxslvalue-of select"cdlabel" /gt ,
• ltxslvalue-of select"cdyear" /gt
• ltxslvalue-of select"cdid" /gt
• lt/fontgt
• ltbr /gt

cd.xsl
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cd.xsl (continued)

• lttablegt
• ltxslfor-each select "track"gt
• lttrgt
• lttd align"left"gt
• ltxslvalue-of select "trknum" /gt
• lt/tdgt
• lttdgt
• ltxslvalue-of select "trktitle" /gt
• lt/tdgt
• lttd align "center" gt
• ltxslvalue-of select "trklen" /gt
• lt/tdgt
• lt/trgt
• lt/xslfor-eachgt
• lt/tablegt
• ltbr /gt
• lt/xslfor-eachgt
• lt/bodygt
• lt/htmlgt

33
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

34
XML and databases

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

35
DBMS requirements

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

36
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

37
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

38
OODBMS

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

39
XML database

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

40
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 a critical data management technology