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XML TUTORIAL

XML TUTORIAL. Portions from w3 schools By Dr. John Abraham. What is XML?. XML stands for E X tensible M arkup L anguage XML is a markup language much like HTML XML was designed to describe data XML tags are not predefined. You must define your own tags. Tags for XML.

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XML TUTORIAL

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  1. XML TUTORIAL Portions from w3 schools By Dr. John Abraham

  2. What is XML? • XML stands for EXtensible Markup Language XML is a markup language much like HTML XML was designed to describe dataXML tags are not predefined. You must define your own tags

  3. Tags for XML <?xml version = “1.0”?> <!Baseball player!> <player> <firstName>John</firstName> <lastName>Doe</lastName> <battingAverage>0.375</battingAverage> </Player> Each element has meaning assigned such as firstName instead of just raw data.

  4. XML Basics • XML uses a Document Type Definition (DTD) or an XML Schema to describe the data XML with a DTD or XML Schema is designed to be self-descriptiveXML is a W3C Recommendation - 1996

  5. XML • Portable, Widely supported, Open technology • Standard for storing data (as text file) that are exchanged between applications. • Not for displaying data • No predefined tags – user supplies tags. • With XML, financial information can be exchanged over the Internet

  6. XML vs. HTML • XML was designed to describe data and to focus on what data is.HTML was designed to display data and to focus on how data looks. • HTML is about displaying information, while XML is about describing information • XML can separate data from HTML

  7. ARTICLE.XML file • <?xml version = "1.0"?> • <!-- Article structured with XML --> • <article> • <title>Simple XML</title> • <date>December 6, 2001</date> • <author> • <firstName>John</firstName> • <lastName>Doe</lastName> • </author> • <summary>XML is pretty easy.</summary> • <content>In this chapter, we present a wide variety of examples that use XML. • </content> • </article>

  8. EXPLANATION • Root element is article • Child elements are title, data, author & summary • To process this file, an XML parser is required, such as msxml (microsoft), Xerces (appache), etc.

  9. XML rules • All XML elements must have a closing tag • With XML, it is illegal to omit the closing tag. • XML tags are case sensitive • All XML elements must be properly nested. Following is wrong: • <b><i>This text is bold and italic</b></i> • All XML documents must have a single root element

  10. XML attributes • XML elements can have attributes in the start tag, just like HTML. • Attribute values must always be quoted • <note date="12/11/2002"> • Avoid using attributes if you can. Use child elements instead.

  11. Processing XML Documents • Requires software called and XML parser • Microsoft xml core services (MSXML) • Apache Xerces • Expat XML Parser • Parser makes data available to applications • Parser verifies syntax

  12. DTD • A Document Type Definition defines the legal building blocks of an XML document. It defines the document structure with a list of legal elements. • A "Valid" XML document also conforms to a DTD. • A "Valid" XML document is a "Well Formed" XML document, which also conforms to the rules of a Document Type Definition (DTD) • A DTD can be declared inline in your XML document, or as an external reference • Your application can use a standard DTD to verify that the data you receive from the outside world is valid. • You can also use a DTD to verify your own data.

  13. Internal DTD • <?xml version="1.0"?> • <!DOCTYPE note [ • <!ELEMENT note (to,from,heading,body)> • <!ELEMENT to (#PCDATA)> • <!ELEMENT from (#PCDATA)> • <!ELEMENT heading (#PCDATA)> • <!ELEMENT body (#PCDATA)> • ]> • <note> • <to>Tove</to> • <from>Jani</from> • <heading>Reminder</heading> • <body>Don't forget me this weekend</body> • </note>

  14. This DTD is interpreted like this: • !DOCTYPE note (in line 2) defines that this is a document of the type note. • !ELEMENT note (in line 3) defines the note element as having four elements: "to,from,heading,body". • !ELEMENT to (in line 4) defines the to element to be of the type "#PCDATA". • !ELEMENT from (in line 5) defines the from element to be of the type "#PCDATA" • and so on.....

  15. External DOCTYPE declaration • If the DTD is external to your XML source file, it should be wrapped in a DOCTYPE definition with the following syntax: • <!DOCTYPE root-element SYSTEM "filename"> • <?xml version="1.0"?> • <!DOCTYPE note SYSTEM "note.dtd"> • <note> • <to>Tove</to> • <from>Jani</from> • <heading>Reminder</heading> • <body>Don't forget me this weekend!</body> • </note> • And this is a copy of the file "note.dtd" containing the DTD: • <!ELEMENT note (to,from,heading,body)> • <!ELEMENT to (#PCDATA)> • <!ELEMENT from (#PCDATA)> • <!ELEMENT heading (#PCDATA)> • <!ELEMENT body (#PCDATA)>

  16. XML Schema XML Schema is an XML based alternative to DTD. • An XML schema describes the structure of an XML document. • The XML Schema language is also referred to as XML Schema Definition (XSD). • An XML Schema: • defines elements that can appear in a document • defines attributes that can appear in a document • defines which elements are child elements • defines the order of child elements • defines the number of child elements • defines whether an element is empty or can include text • defines data types for elements and attributes • defines default and fixed values for elements and attributes

  17. A Simple XML Schema • This is a simple XML Schema file called "note.xsd" that defines the elements of the XML document above ("note.xml"): • <?xml version="1.0"?> • <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" • targetNamespace="http://www.w3schools.com" • xmlns="http://www.w3schools.com" • elementFormDefault="qualified"><xs:element name="note"> • <xs:complexType> • <xs:sequence> • <xs:element name="to" type="xs:string"/> • <xs:element name="from" type="xs:string"/> • <xs:element name="heading" type="xs:string"/> • <xs:element name="body" type="xs:string"/> • </xs:sequence> • </xs:complexType> • </xs:element></xs:schema>

  18. Viewing XML files • Raw XML files can be viewed in Mozilla, Firefox, Opera, Internet Explorer, and in Netscape 6+. • However, to make XML documents to display like nice web pages, you will have to add some display information • With CSS (Cascading Style Sheets) you can add display information to an XML document. • Look at this XML file: Look at this XML file: note.xml

  19. Displaying XML files with CSS • Take a look at this XML file: The CD catalog • Then look at this style sheet: The CSS file • Finally, view: The CD catalog formatted with the CSS file • XSL (the eXtensible Stylesheet Language) is the preferred style sheet language of XML. • View the XML file, the XSL style sheet, and View the result.

  20. XSLT XSLT (Extensible Stylesheet Language Tranformation) is a language for transforming XML documents into XHTML documents or to other XML documents. • XSLT is the most important part of XSL • XSLT transforms an XML document into another XML document • XSLT uses XPath to navigate in XML documents

  21. XML namespaces • Collection of elements and attribute names. • Provide a means for document authors to unambigously refer to elements with same name. • <client:name> • <student:name> • Use namespace prefix and a colon. • Use default namespace – then namespace colon not necessory.

  22. Please refer to Ch 14 for additional descriptions on XML

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