Enabling Data Exchange with XML

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IA307 - Data Exchange with XML
Christophe Coenraets Manager, Technical
Evangelists Internet Applications
Division ccoenrae_at_sybase.com
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Topics

• Drawbacks of HTML
• What is XML?
• Document Type Declaration (DTD)
• Extensible Style Language (XSL)
• XML and Java
• Simple API for XML (SAX)
• Document Object Model (DOM)

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TripFinder.htm Page

• ltcentergtlth1gtTrip Finderlt/h1gt
• ltform action"TripFinder.jsp"gt
• lttable border0gt
• lttrgtlttdgtOriginlt/tdgtlttdgtltinput name"origin"
  value"bos"gtlt/tdgtlt/trgt
• lttrgtlttdgtDestinationlt/tdgtlttdgtltinput
  name"destination" value"ARU"gtlt/tdgtlt/trgt
• lttrgtlttdgtDatelt/tdgtlttdgtltinput name"date"
  value"01/01/1900"gtlt/tdgtlt/trgt
• lt/tablegtltbrgtltinput type"submit"
  value"Search"gtlt/formgt
• ltpgtlttable border1 cellpadding4gt
• lttrgtlttdgtlta hrefPayment.jsp?trip2amount2200gtBoo
  k itlt/agtlt/tdgt
• lttdgtTNTlt/tdgtlttdgtGrand Hyatt Arubalt/tdgtlttdgt2000-05-
  01lt/tdgtlttdgt7lt/tdgtlttdgt2200lt/tdgtlt/trgt
• lttrgtlttdgtlta hrefPayment.jsp?trip8amount1900gtBoo
  k itlt/agtlt/tdgt
• lttdgtTNT lt/tdgtlttdgtPlaza Hotellt/tdgtlttdgt2000-06-01lt/t
  dgtlttdgt7lt/tdgtlttdgt1900lt/tdgtlt/trgt
• lttrgtlttdgtlta hrefPayment.jsp?trip9amount2100gtBoo
  k itlt/agtlt/tdgt
• lttdgtGWVlt/tdgtlttdgtMarriott Arubalt/tdgtlttdgt2000-06-01lt
  /tdgtlttdgt7lt/tdgtlttdgt2100lt/tdgtlt/trgt
• lt/tablegtlt/centergt

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Drawbacks of HTML

• HTML document contains both data and formatting
• HTML tags
• Describe how page elements should look
• Don't contain any information about what the data
  is
• Issues
• Difficult to identify and extract data from the
  document
• Difficult to change the presentation style

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What is XML?

• Extensible Markup Language
• World Wide Web Consortium standard that lets you
  create your own tags
• Universal data description mechanism
• XML separates the data and presentation
• Makes documents suitable for data interchange
• Allows alternative presentation styles
• Simplifies business-to-business transactions on
  the web

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XML DocumentTrip.xml

• lt?xml version"1.0" ?gt
• lttripgt
• lttrip_idgt2lt/trip_idgt
• ltorigingtBOSlt/origingt
• ltdestinationgtARUlt/destinationgt
• lthotelgtGrand Hyatt Arubalt/hotelgt
• ltarrival_dategt2000-05-01lt/arrival_dategt
• ltdaysgt7lt/daysgt
• ltpricegt2200lt/pricegt
• lt/tripgt

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XML Document Characteristics

• No presentation information
• No specification of type style or color
• No specification of format table, list, bold,
  etc
• Tags are application-oriented
• ltdestinationgt, lthotelgt, etc, instead of just ltpgt
• Easy to distinguish 123 as TripId vs Price

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Enabling Business-to-Business (B2B)
ltTripRequestgt lt/TripRequestgt
Tour Operator
ltTripListgtlt/TripListgt
Travel Agent
TripList.xmlTripList.xsl
ltTripListgtlt/TripListgt
Tour Operator
ltTripRequestgt lt/TripRequestgt
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Well Formed XML documents

• An XML document is well-formed if it is
  syntactically correct
• Document starts with lt?xmlgt
• Tags are strictly nested
• Each open lttaggt has a corresponding close lt/taggt

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Valid XML documents

• An XML document is valid if it specifies and
  conforms to the document rules defined in a DTD
• Valid XML documents are well-formed
• Well-formed XML documents may be valid

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Document Type Declaration (DTD)

• Specifies a Document Type
• Defines set of rules, grammar document must
  comply to
• Allows for predictable data

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Vacation DTDExample

• lt!ELEMENT trip (origin, destination, hotel,
  arrival, nights, price)gt
• lt!ELEMENT origin (PCDATA)gt
• lt!ELEMENT destination (PCDATA)gt
• lt!ELEMENT hotel (PCDATA)gt
• lt!ELEMENT arrival (PCDATA)gt
• lt!ELEMENT nights (PCDATA)gt
• lt!ELEMENT price (single, double)gt
• lt!ELEMENT single (PCDATA)gt
• lt!ELEMENT double (PCDATA)gt
• lt!ATTLIST hotel rating (na1234) "na"gt

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XML DocumentTrips.xml

• lt?xml version"1.0" ?gt
• lt!DOCTYPE vacation SYSTEM "vacation.dtd"gt
• lttripsgt
• lttripgt
• lttrip_idgt2lt/trip_idgt
• ltorigingtBOSlt/origingt
• ltdestinationgtARUlt/destinationgt
• lthotelgtGrand Hyatt Arubalt/hotelgt
• ltarrival_dategt2000-05-01lt/arrival_dategt
• ltdaysgt7lt/daysgt
• ltpricegt2200lt/pricegt
• lt/tripgt
• lt/tripsgt

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Presentation Using XSL

• XML documents omit all formatting
• Formatting is supplied by XSL
• XSL Extensible Style Language
• Specified separate from the XML document
• Allows multiple XSL specs for one XML document
• An XSL spec maps
• An XML document type to HTML, or
• One XML document type to another

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XML and Java

• Java and XML are complementary Technologies
• Java Code Portability
• XML Data Portability
• Java Parsers facilitate XML document manipulation
• Validate an XML document
• Handle character set issues, etc
• Return a Java object (a tree) for the document
• Also used to build such a tree and generate a
  document

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XML Parsers

• Many XML parsers are available
• Often with free license or public domain
• XML parsers use two standard interfaces
• SAX and DOM
• Applications using SAX DOM
• Can be portable across XML parsers

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Simple API for XML (SAX)

• Event-driven interface to XML parsers
• org. xml. sax. package

Event
lt?xml version"1.0" ?gt lttripgt lt/tripgt
Event
SAX
Event
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Document Object Model (DOM)

• Tree data structure interface to XML parser
• Models document structure as objects
• Defines a Java programming language binding
• org. w3c. dom. package
• DOM is also used to build XML documents

lt?xml version"1.0" ?gt lttripgt lt/tripgt
DOM
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Creating TripListXML.jspDemo
Tour Operator
ltTripListgtlt/TripListgt
Travel Agent
TripList.xmlTripList.xsl
ltTripListgtlt/TripListgt
Tour Operator
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Summary