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XML. eXtensible Markup Language w3c standard Why? Store and transport data Easy data exchange Create more languages WSDL (Web Service Description Language) RDF (Resource Description Framework) RSS (Really Simple Syndication) Self-describing data Easy to learn Must learn.
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XML • eXtensible Markup Language • w3c standard • Why? • Store and transport data • Easy data exchange • Create more languages • WSDL (Web Service Description Language) • RDF (Resource Description Framework) • RSS (Really Simple Syndication) • Self-describing data • Easy to learn • Must learn
3 Major Components • XML • XSL (eXtensible Stylesheet Language) • Style sheet language for XML documents • XSD (XML Schema Definition) • Describes the structure of an XML document
XML Document <?xml version="1.0"?> <!-- this is a sample --> <note> <to>Tove</to> <from source=”contacts”>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> Processing Instruction Comment Element Attribute
XML Documents • Well formed and Valid • Well formed • Should only contain one root element • All tags should have corresponding end tag • Tags never overlap(<author><name> … </author></name>) • Attributes must be quoted • Valid • Must be well formed and conforms to the schema
XML Documents • Has tree structure • Tags are case sensitive • <name> is different from <Name> • Comments <!-- this is a comment -->
XML Elements • Can contain • Other elements • Text • Attributes • Valid names • <name>, <first_name>, <first2names> • Invalid names • <2nd_name>, <$amount>, <firstname>
XML elements and Attributes • Data goes as elements • <person><name>john</name></person> • Meta data goes as attributes • <image type='gif'><name>graph.gif</name></image>
1.0 vs 1.1 • 1.0 – everything not permitted is forbidden • 1.1 – everything not forbidden is permitted • 1.0 is compatible with 1.1, not vise-versa • Forward compatible • Does not affects to English documents
XML Namespaces • There can be common elements in multiple domains • File in hardware and office <file> <length>18</length> <price>3.69</price> <file> <file> <content>Employee data</content> <numberOfPages>25</numberOfPages> </file>
XML Namespaces • How to distinguish? • Solution : namespaces <h:file xmlns:h="http://www.hardware.com/"> <h:length>18</h:length> <h:price>3.69</h:price> <h:file> <o:file xmlns:o="http://www.office.com/people"> <o:content>Employee data</o:content> <o:numberOfPages>25</o:numberOfPages> </o:file>
XML Parsers • A piece of software which reads the content from the XML documents and present it to the application • Implementing xml parser • Java way • SAX (Simple API for XML) • DOM (Document Object Model) • StAX (Streaming API for XML)
XML Parsers • XML Parser Demos