XML in the Real World perl, xml and oakley'com

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XML in the Real Worldperl, xml and oakley.com

• by Ryan Erwin

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Overview

• Perl
• XML
• XPath
• XML Schema
• XSLT
• XML Indexes
• AxKit, SAWA

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Perl in Business Applications

• Flexible - TIMTOWTDI
• Fast Development
• Versatile
• Dictionary capable of doing many things
  competently
• Easy things Easy - Hard things possible
• Balance between power and ease of use
  suitable for business applications
• Fun
• I enjoy solving problems with Perl
• Efficient
• Others really enjoy their work with Perl

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XML / Use Cases

• Standardized Data Interchange
• EDI Replacements
• Web Services - Remote Function Calls
• XML-RPC and SOAP
• Document File Formats
• OpenOffice Word Processor
• SVG (for Flash and Illustrator some day?)
• Configuration Files
• Database Alternative
• XML-RDBMS
• Xindice (Zeen-dee-chay)
• ECommerce Product Catalog

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XML / Overview

• XML stands for eXtensible Markup Language
• XML is a markup language much like HTML
• XML was designed to describe data
• XML tags are not predefined in XML - youre free
  to define your own tags
• Remember XML does NOT do anything
• XML was created as a way to structure, store, and
  send information

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XML / File Types

• XML Data Files
• Data Oriented
• Element Nodes are usually not nested inside Text
  Nodes
• Can be visualized as a Spread Sheet (via XML Spy)
• Higher correlation with Entity-Relationship Model
• XML Document Files
• Presentation Oriented
• More like HTML
• Formatting Information (bold, italic, underline,
  color, etc)
• Stylesheets
• Difficult to visualize as a Spread Sheet

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XML / Attributes and Elements

• Use Elements whenever Possible
• Attributes are best used for Data Type
  Information attached to Elements
• Exampleltname firstryan lasterwin/gt-or-ltn
  amegt ltfirstgtryanlt/firstgt ltlastgterwinlt/lastgtlt/
  namegt

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XML / Attribute and Elements (cont)

• ltnamegt ltfirstgtryan ltetymologygtlittle
  kinglt/etymologygt lt/firstgt ltlastgterwin
  ltetymologygtfriend of the wild boarlt/etymologygt
  lt/lastgtlt/namegt

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XML / Database Alternative

• Low Cost
• Easy to Create
• No database server required
• Neither does Berkley DB or Embedded MySQL
• Easy to Change
• Easy to Make a Mess

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XML - DB - Change

• XML is just a text file
• exceptions can apply to a single file
• databases require schema changes when one special
  case breaks the previously established rules
• this is power - it can be well used or well
  abused
• Additions can easily be made to a schema without
  breaking existing code
• recall XML Attribute and Element Example

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XPath

• Query Language for XML
• Locate Information inside an XML Document
• XPath querys the data in a loaded nodeset - it
  cant find data that isnt yet loaded
• If you had an XML document containing a Map of
  the world, an XPath expression might look like
• US/CA/Foothill Ranch/Icon/One/Building/Auditorium
• XPath specifies a route rather than pointing to a
  specific set or sequence of characters, words, or
  other elements

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W3 XML Schema

• XML Based Data Validation Tool
• Alternative to XML DTD - Document Type Definition
• XML Spy Integration
• Not widely accepted / implemented
• Much more powerful than DTD
• RegEx validation against element content

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W3 XML Schema Example

• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdsimpleType name"path_absolute_type"gt lt
  xsdrestriction base"xsdstring"gt
• ltxsdpattern value
• (/xml/product/)1(_a-z0-9_\./)1,index.xml
  " /gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdschemagt

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XSLT

• Separate Content from Presentation
• One Document - Many Purposes
• The LA Times presents News Stories and
  Advertisements
• These are presented in the Newspaper and Website
• If all of the content is well organized in XML
  the Times would
• use Newspaper.xsl and send the output to the
  printing press
• use Website.xsl and send the output to the screen

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XSLT (cont)

• XML Language for Transforming XML Documents
• Many Implementations
• Very Fast, if using LibXSLT from RedHat
• Limited set of functions and power by design

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XSLT (cont)

• Programming without Assignments
• Useless for XSL with Pull Method
• PurposeDownload entire XSL File but start
  displaying an XML file when only a portion of the
  file has been downloaded

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XSLT / Models

• Push
• Event Driven by Template Matching Rules and Apply
  Templates
• More Similar to SAX
• XML DocBook
• Little Control over XSL output
• Pull
• More Similar to DOM
• Grab specific items of interest out of an XML
  document
• Very useful when multiple rules may be needed for
  one element
• Lots of Control over XSL output

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XSLT Example

• /Desktop/Presentation/XSLT

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XML Product Database

• Business Requirements always Change
• at least they do here )
• XML allows flexibility to grow
• Data Administration with XML Spy
• often able to avoid tools required to bootstrap
  your tools with data these tools also need to
  be changed as your application changes
• Flexibility to Make Exceptions
• Most eyewear is defined by a product name, lens
  color and frame color
• Oakley M-Frame and Why-3 also have a lens shape
• XML allows us to avoid complicating all of the
  normal products just to accommodate exceptions
• More Efficient way to solve many problems

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XML Product Database (cont)

• If resources were infinite and requirements never
  changed I would recommend using an RDBMS over XML
  any day
• If you live in such a world, Im happy for you -
  never leave )
• If you dont, then dont worry about building the
  perfect schema that will inevitably break, take
  a swing at defining a good enough XML Schema
  and let it grow with your needs

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MySQL XML Index

• Huge XML Drawback
• XML isnt automatically indexed
• Workaround
• Build a database schema that represents the
  required parts of your XML
• Build a tool to dump your XML into that database
  for searching
• Dont bother trying to generically convert your
  XML into an RDBMS and back
• you will loose everything that XML gives you
• Think of the relationship of your XML to your
  Database like a Photoshop file is to a JPEG
• Xindice and other projects will fix this in the
  future

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XML and Friends

• XML is just another tool...
• Java, EJBs, JDBC, etc
• Perl, DBI, Data Access Modules
• Perl, XML, XSLT, Schema, XmlSpy
• Microsoft Access

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The End

• Questions
• Comments
• Tips )