Xml
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The document defines XML as a markup language for structured data similar to HTML but designed to carry data rather than display it. XML uses user-defined tags rather than predefined tags. It was introduced in 1998 by the W3C and is used widely on the web to transport and share data between applications. XML separates data from formatting and simplifies data sharing, transport, and platform changes by making data more available.
Xml
- 2. WHAT IS XML? eXtensible Markup Language markup language for documents containing structured information much like HTML XML was designed to carry data, not to display data XML tags are not predefined. You must define your own tags Based on Standard Generalized Markup Language (SGML) Version 1.0 introduced by World Wide Web Consortium (W3C) in 1998 Bridge for data exchange on the Web 2
- 3. WHAT IS XML? a method for putting structured data into a text file; these files are: Easy to read Unambiguous Extensible software- and hardware-independent tool for carrying information. self-descriptive 3
- 4. WHAT IS XML? XML is Not a Replacement for HTML In most web applications, XML is used to transport data, while HTML is used to format and display the data. 4
- 5. HOW CAN XML BE USED? XML Separates Data from HTML XML Simplifies Data Sharing XML Simplifies Data Transport XML Simplifies Platform Changes XML Makes Your Data More Available XML is Used to Create New Internet Languages XHTML WSDL for describing available web services WAP and WML as markup languages for handheld devices RSS languages for news feeds 5
- 6. If Developers Have Sense If they DO have sense, future applications will exchange their data in XML. 6
- 7. COMPARISONS Extensible set of tags Content orientated Allows multiple output forms Fixed set of tags Presentation oriented Single presentation XML HTML 7
- 8. AUTHORING XML ELEMENTS An XML element is made up of a start tag, an end tag, and data in between. Example: <director> Matthew Dunn </director> Example of another element with the same value: <actor> Matthew Dunn </actor> XML tags are case-sensitive: <CITY> <City> <city> XML can abbreviate empty elements, for example: <married> </married> can be abbreviated to <married/> 8
- 9. AUTHORING XML DOCUMENTS A basic XML document is an XML element that can, but might not, include nested XML elements. Example: <books> <book isbn=“123”> <title> Second Chance </title> <author> Matthew Dunn </author> </book> </books> 9
- 10. XML DATA MODEL: EXAMPLE <BOOKS> <book id=“123” loc=“library”> <author>Hull</author> <title>California</title> <year> 1995 </year> </book> <article id=“555” ref=“123”> <author>Su</author> <title> Purdue</title> </article> </BOOKS> Hull Purdue BOOKS 123 555 California Su titleauthor title author article book year 1995 ref loc=“library” 10
- 11. XML EXAMPLE <?xml version="1.0" encoding="ISO-8859-1"?> <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> 11
- 12. XML SYNTAX RULES All XML Elements Must Have a Closing Tag In HTML, some elements do not have to have a closing tag: <p>This is a paragraph <p>This is another paragraph In XML, it is illegal to omit the closing tag. All elements must have a closing tag: <p>This is a paragraph</p> <p>This is another paragraph</p> 12
- 13. XML SYNTAX RULES XML Tags are Case Sensitive XML tags are case sensitive. The tag <Letter> is different from the tag <letter>. Opening and closing tags must be written with the same case: <Message>This is incorrect</message> <message>This is correct</message> 13
- 14. XML SYNTAX RULES XML Elements Must be Properly Nested In HTML, you might see improperly nested elements: <b><i>This text is bold and italic</b></i> In XML, all elements must be properly nested within each other: <b><i>This text is bold and italic</i></b> 14
- 15. XML SYNTAX RULES XML Documents Must Have a Root Element XML documents must contain one element that is the parent of all other elements. This element is called the root element. <root> <child> <subchild>.....</subchild> </child> </root> 15
- 16. XML SYNTAX RULES XML Attribute Values Must be Quoted XML elements can have attributes in name/value pairs just like in HTML. In XML, the attribute values must always be quoted. Incorrect: <note date=12/11/2007> <to>Tove</to> <from>Jani</from> </note> Correct: <note date="12/11/2007"> <to>Tove</to> <from>Jani</from> </note> 16
- 17. XML SYNTAX RULES : ENTITY REFERENCES special meaning of Some characters in XML. Error in XML: <message>if salary < 1000 then</message> To avoid this error, replace the "<" character with an entity reference: <message>if salary < 1000 then</message> There are 5 predefined entity references in XML: < < less than > > greater than & & ampersand ' ' apostrophe " " quotation mark Note: Only the characters "<" and "&" are strictly illegal in XML. The greater than character is legal, but it is a good habit to replace it. 17
- 18. Comments in XML The syntax for writing comments in XML is similar to that of HTML. <!-- This is a comment --> XML Syntax Rules 18
- 19. White-space is Preserved in XML HTML truncates multiple white-space characters to one single white-space: HTML: Hello Tove Output: Hello Tove XML: the white-space in a document is not truncated. Hello Tove Output: Hello Tove XML Syntax Rules 19
- 20. XML Stores New Line as LF Windows applications : a new line -> carriage return (CR) and line feed (LF). Unix applications : a new line -> LF character Macintosh applications : a new line -> LF character XML stores a new line as LF. XML Syntax Rules 20
- 22. XML DECLARATION The XML declaration looks like this: <?xml version="1.0" encoding="UTF-8" standalone="yes"?> The XML declaration is not required by browsers, but is required by most XML processors (so include it!) If present, the XML declaration must be first--not even whitespace should precede it Note that the brackets are <? and ?> version="1.0" is required (this is the only version so far) encoding can be "UTF-8" (ASCII) or "UTF-16" (Unicode), or something else, or it can be omitted standalone tells whether there is a separate DTD 22
- 23. An element can contain: other elements text attributes or a mix of all of the above... XML Elements 23
- 24. <bookstore> <book category="CHILDREN"> <title>Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price> </book> <book category="WEB"> <title>Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book> </bookstore> XML Elements 24
- 25. XML elements must follow these naming rules: Names can contain letters, numbers, and other characters Names cannot start with a number or punctuation character Names cannot start with the letters xml (or XML, or Xml, etc) Names cannot contain spaces XML Elements Naming Rules 25
- 26. <person sex="female"> <firstname>Anna</firstname> <lastname>Smith</lastname> </person> <person> <sex>female</sex> <firstname>Anna</firstname> <lastname>Smith</lastname> </person> XML Elements vs. Attributes 26
- 27. 1) <note date="10/01/2008"> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> XML Elements vs. Attributes 27
- 28. 2) <note> <date>10/01/2008</date> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> XML Elements vs. Attributes 28
- 29. 3) <note> <date> <day>10</day> <month>01</month> <year>2008</year> </date> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> XML Elements vs. Attributes 29
- 30. Some of the problems with using attributes are: attributes cannot contain multiple values (elements can) attributes cannot contain tree structures (elements can) attributes are not easily expandable (for future changes) Attributes are difficult to read and maintain. Use elements for data. Use attributes for information that is not relevant to the data. Avoid XML Attributes? 30
- 32. XML with correct syntax is "Well Formed" XML. XML validated against a DTD or XMLSchema is "Valid" XML. XML Validation 32
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