SPECIAL TOPIC

XML

Introducing XML

XML (eXtensible Markup Language)

◦ A language used to create structured documents XML vs HTML ◦ XML is designed to transport and store data (carry) ◦ ◦ ◦ ◦ HTML was designed to display data (show) Shares common structure with HTML documents Elements are indicated with markup tags that contain textual content; element names are descriptive A markup tag can contain attributes that describe a feature of the element, and a single root element contains all other elements in the document

Introducing XML

XML does not DO anything. XML was created to structure, store, and transport information.

The following example is a note to Tove, from Jani, stored as XML < to>Tove < from>Jani < heading>Reminder < body>Don't forget me this weekend! < /note>

XML Tree Structure

With XML You Invent Your Own Tags

◦ the XML language has no predefined tags XML documents form a tree structure that starts at "the root" and branches to "the leaves".

.

.

.

Introducing XML

XML declaration

It defines the XML version (1.0) and the encoding used (UTF-8).

Single root element (students) Student, name, and photo elements and the id and grade attributes provide information about individual students

o o o o o o o o

Syntax Rules

Must have closing tags Case sensitive tags Proper tag nesting Must have a Root element Attributes must be quoted Uses HTML comments Special symbols > < & ‘ “ Use entity references: < >

Syntax Rules

Comments are similar to HTML comment White-space is Preserved in XML Naming rules ◦ 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 ◦ Any name can be used, no words are reserved

XML Elements

An XML element is everything from (including) the element's start tag to (including) the element's end tag An element can contain: ◦ other elements ◦ text ◦ attributes ◦ or a mix of all of the above < book category="CHILDREN"> J K. Rowling 2005 29.99 < /book> < /bookstore>

XML attributes

XML elements can have attributes.

◦ Attributes provide additional information about an element.

computer.gif

XML Elements vs. Attributes

Take a look at these examples: < person sex="female"> Anna Smith < /person> < person> female Anna Smith < /person>

Attributes vs. Elements

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, and attributes for information that is not relevant to the data

Namespaces

XML Namespaces provide a method to avoid element name conflicts Defined by the xmlns attribute Tags that are not HTML tags have the prefix xsl, identified by the namespace xmlns:xsl="http://www.w3.org/1999/XSL/Transform": Name conflicts in XML can easily be avoided using a name prefix xmlns:h="http://www.w3schools.com/html4"> xmlns:f="http://www.w3schools.com/furniture">

e

X

tensible

S

tyle sheet

L

anguage

T

ranslation

.XSLT

Styles

Can use a CSS style sheet to format an XML document Better approach is to use XSL (eXtensible Stylesheet Language) ◦ can transform an XML document into HTML, using ◦ XSLT (eXtensible Stylesheet Language Transformation)

Transforming XML with XSLT

Extensible Stylesheet Language Transformation (XSLT)

◦ A style language developed for XML documents ◦ Allows developers to easily transform contents of an XML document into another document format ◦ A more efficient approach to transforming an XML document into HTML format than working with the document object model

The Element

The match attribute is used to associate a template with an XML element < xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> match="/" indicates the stylesheet template applies to the entire XML file < xsl:template match="/">

My CD Collection

Title	Artist
.	.

< /xsl:template> < /xsl:stylesheet>

Used to extract the value of an XML element and add to output.

< xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> < xsl:template match="/">

My CD Collection

select=" catalog/cd/artist "/>

Title
Artist

< /xsl:template>

< /xsl:stylesheet>

The Element

Allows you to do looping < xsl:stylesheet version="1.0“ xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> < xsl:template match="/">

My CD Collection

Title	Artist

< /xsl:template> < /xsl:stylesheet>

XSLT Element used to sort the output

< xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> < xsl:template match="/">

My CD Collection

Title	Artist

< /xsl:template> < /xsl:stylesheet>

XSLT Element

used to put a conditional test against the content of the XML file < xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> < xsl:template match="/">

My CD Collection

< xsl:if test="price > 10">

Title	Artist
< xsl:value-of select="title "/>	< xsl:value-of select="artist "/>

< /xsl:template> < /xsl:stylesheet>