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Introduction to XML• XML stands for Extensible Markup Language. Because it is

extensible, XML has been used to create a wide variety of different markup vocabularies.

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CML: An XML Example

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GolfML: Another XML Example

<?xml version="1.0" encoding="utf-8"?><golfml xmlns="http://pga.com/golfml">

<course name=“The Oaks”> <tee num=“1”> <par>5</par> <handicap>15</handicap> <length units=“yds”>475</length> </tee> <tee num=“2”> … </tee> </course></golfml>

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Why is XML Important?

• XML gives us a way to create and maintain structured documents in plain text that can be rendered in a variety of different ways.

• A primary objective of XML is to completely separate content from presentation.

Example: The Asbury Park Press is a structured document containing pages, columns, etc.

The news is just plain text (including the images).

Newspapers can be rendered on paper or online.

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Where XML Fits into Other Markup Languages

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DTDs and XML Documents

• A DTD (Document Type Definition) or schema specifies the rules for what a legal XML document may contain.

• An XML document is well-formed if it contains no syntax errors and fulfills all of the specifications for XML code as defined by the W3C.

• An XML document is valid if it is well-formed and also satisfies the rules laid out in the DTD or schema attached to the document.

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The Structure of an XML Document: The Prolog

• The XML declaration is always the first line of code in an XML document. It tells the parser what follows is written using XML.

• The complete syntax is:<?xml version=“version number”

encoding=“encoding type” standalone=“yes | no” ?>

• The typical declaration is:<?xml version=“1.0” encoding=“UTF-8”

standalone = “yes” ?>

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• Closed elements have the following syntax:

<element_name>Content</element_name>For example: <Artist>Miles Davis</Artist>

• Open elements have the syntax: <element /> For example: <Jazz_Music />

• Element names are case sensitive, must begin with a letter (or _), and may not contain spaces.

• Elements can be (properly) nested. For example:

<playlist> <track>So What</track> <track>Blue in Green</track>

</playlist>• All elements must be nested within a single root element. • Comments are enclosed in <!-- comment --> (like HTML).

The Structure of an XML Document: Elements

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• An attribute is a property of an element. They are text strings placed in single or double quotes. The syntax is:

<element_name attribute=“value”>

The Structure of an XML Document: Attributes

The Element Hierarchy

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Special Character References

Special symbols can be inserted into an XML document using either the character reference or entity reference,

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CDATA Sections

• Validators can get confused by some XML:<temperatureRange>

> 100 degrees</temperatureRange>

• You must separate the file into PCDATA and CDATA.

• Parsed character data (PCDATA) is text to be parsed by a browser or parser (all the XML code: declarations, elements, attributes, comments).

• Unparsed character data (CDATA) is text not to be processed by the browser or parser. A CDATA section marks a block of text as CDATA so that parsers ignore any text within it:

<temperatureRange> <![CDATA[ > 100 degrees ]]> </temperatureRange>

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Mark Your XML with the Sections You Don’t Want Parsed

CDATA section

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Parsing an XML Document

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Displaying an XML Document in a Web Browser

If it’s well-formed

If it’s not well-formed

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Linking to a Style Sheet

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Applying Styles to the XML Elements

• To apply a style sheet to a document, use the syntax:

selector {attribute1:value1; attribute2:value2; …}

For example: artist {color:red; font-weight:bold}

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Linking the XML to the Style Sheet

• The link from the XML document to a style sheet is created using a processing statement. A processing instruction is a command that gives instructions to the XML parser.

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The XML Document Formatted with the Style Sheet