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XML

XML. e X tensible M arkup L anguage. http://www.w3schools.com/xml http://www.cafeconleche.org. 1/23. What is XML. stands for e X tensible M arkup L anguage a markup language much like HTML designed to describe data tags not predefined you must describe your own tags

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XML

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  1. XML eXtensibleMarkupLanguage http://www.w3schools.com/xml http://www.cafeconleche.org 1/23

  2. What is XML • stands foreXtensibleMarkupLanguage • amarkup languagemuch like HTML • designed todescribe data • tags not predefined • you mustdescribe your own tags • uses aDocument Type Definition(DTD) or anXML Schemato describe data 2/23

  3. XML and HTML • different goals • HTML designed todisplay data • how data looks • about displaying information • XML designed todescribe data • what data is • about describing information • structuring, storing & sending information 3/23

  4. XML doesn’t do anything what does XML do? • XML can be used to exchange data • many different applications • over the internet • XML can be used to create new languages • WAP (Wireless Application Protocol) • WML (Wireless Markup Language) 4/23

  5. a cross-platform, software & hardware independent tool for transmitting information XML 5/23 5/23

  6. 9 XML example <?xml version=“1.0” encoding=“ISO-8859-1”?> <car make=“Honda Jazz”> <model>Vti </model> <engine capacity>1.3 litres</engine capacity> <max power>81kW @ 6000 rpm</max power> <fuel tank capacity> <quantity> 42 </quantity> <units>litres</units> </fuel tank capacity> </car> 6/23

  7. XML syntax • XML declaration • root element • XML elements 7/23

  8. XML elements • everything from (including) start tag to (including) end tag • tags are case sensitive • <LETTER> != <letter> • can have sub elements <root> <child> <subchild> … </subchild> </child> </root> 8/23

  9. 7 XML attributes • XML elements can have attributes • in the start tag • <student SID= “123456”> • <polygon name= “square” colour= “red” > • additional information about elements • not part of data • elements or attributes? 9/23

  10. elements or attributes • example 1 – date attribute • <letter date=‘1/9/05’> • <contents> ….. </contents> • </letter> • example 2 - date element • <letter> • <date> 1/9/05 </date> • <contents> ….. </contents> • </letter> • example 3 – expanded date element • <letter> • <date> • <day> 1 </day> • <month> 9 </month> • <year> 05 </year> • </date> • <contents> ….. </contents> • </letter> 10/23

  11. avoid attributes • cannot contain multiple values • not easily expandable – future • cannot describe structures • more difficult to read 11/23

  12. metadata should be stored as attributes the data should be stored as elements rule of thumb 12/23

  13. XML validation • XML with correct syntax is Well Formed • a DTD (Document Type Definition) defines the legal contents of an XML document • an XML schema is an alternative to a DTD 13/23

  14. XML schemas • ability to specify data types for content and attribute values • ability to validate complex structures • namespace awareness 14/23

  15. why not DTDs • no data typing ability • e.g. can’t say element must be an integer 1-12 • non-XML syntax • cannot be parsed by same parser • difficult to modularize and combine • cannot enforce order or number of child elements 15/23

  16. what is a schema • hypothetical outline - pattern • document that describes permissible content of a database • many schema languages for XML • W3C XML Schema Language • by convention – in .xsd extension 16/23

  17. schema example <?xml version=“1.0”?> <?xml version=“1.0”?> <GREETING> <GREETING> Hello XML! How are you? </GREETING> </GREETING> <?xml version=“1.0”?> <xsd:schema xmlns:xsd=“http://www.w3.org/2001/XML Schema”> <xsd:element name=“GREETING” type=“xsd:string”> </xsd:schema> <?xml version=“1.0”?> <GREETING xsi:noNamespaceSchemaLocation=“Greeting.xsd” xmlns:xsi=“http://www.w3.org/2001/XML Schema - instance”> Hello XML! </GREETING> 17/23

  18. schema structure • root element-schema • usually namespace bound to prefix xsd or xs • elements declared usingxsd:element • name attribute specifies which element declared • type attribute declares data type • attach schema to XML document by adding xsi:noNamespaceSchemaLocationattribute to the document’s root element 18/23

  19. 20 XML example <?xml version=“1.0” encoding=“ISO-8859-1”?> <car make=“Honda Jazz”> <model>Vti</model> <engine capacity>1.3 litres</engine capacity> <max power>81kW @ 6000 rpm</max power> <fuel tank capacity> <quantity>42 </quantity> <units>litres</units> </fuel tank capacity> </car> 19/23

  20. 19 schema example <?xml version=“1.0”?> <xsd:schema xmnls:xsd=“http://www.w3.org/2001/XML Schema”> <xsd:element name=“car” type=“vehicletype” /> <xsd:complexType name=“vehicletype”> <xsd:attribute name=“make” type=“xsd:string/> <xsd:sequence> <xsd:element name=“model” type=“xsd:string”/> <xsd:element name=“engine capacity” type=“xsd:string”/> <xsd:element name=“max power ” type=“xsd:string”/> <xsd:element name=“fuel tank capacity”> <xsd:complexType> <xsd:sequence> <xsd:element name=“quantity” type=“xsd:positiveInteger”/> <xsd:element name=“units” type=“xsd:string”/> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:sequence> </xsd:complexType> </xsd:schema> 20/23

  21. 22 XML example <?xml version=“1.0” encoding=“ISO-8859-1”?> <building id=“myHouse”> <type>house</type> <no. of storeys>3</no. of storeys> <area>180</area> <component>storey1</component <component>storey2</component> <component>storey3</component> </building> 21/23

  22. 21 schema example <?xml version=“1.0”?> <xsd:schema xmnls:xsd=“http://www.w3.org/2001/XML Schema”> <xsd:element name=“building”> <xsd:complexType> <xsd:attribute name=“id” type=“xsd:string/> <xsd:sequence> <xsd:element name=“type” type=“xsd:string”/> <xsd:element name=“no.of storeys” type=“xsd:positiveInteger” maxInclusive=“4”/> <xsd:element name=“area ” type=“xsd:float”/> <xsd:element name=“component” type=“xsd:string maxOccurs=“unbounded”/> </xsd:sequence> </xsd:complexType> </xsd:element> </xsd:schema> 22/23

  23. aecXML • working group – 1999 • for exchange of AEC specific information • http://xml.coverpages.org/aecXML.html • XML schemas for communication • designing, specifying, estimating, sourcing, installing & maintaining products & materials over the Internet • AISC steel information in XML • Bentley -2001 • aecXML & IFC • http://www.cadinfo.net/editorial/aecxml.htm 23/23

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