Life of IT Professionals in Sydney. Computing Articles.

1) What is XML

XML stands for EXtensible Markup Language

XML is a markup language much like HTML

XML was designed to carry data, not to display data

XML tags are not predefined. You must define your own tags

XML is designed to be self-descriptive

XML is a W3C Recommendation

2) Example of XML

<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

3) XML must have root element

4) Entity reference

<	<	less than
>	>	greater than
&	&	ampersand
'	'	apostrophe
"	"	quotation mark

5) Comments in xml

The syntax for writing comments in XML is similar to that of HTML.

6) White space is preserved in xml

With XML, the white-space in a document is not truncated.

7) What is an xml element

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...

<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>

In the example above, <bookstore> and <book> have element contents, because they contain other elements. <book> also has an attribute (category="CHILDREN"). <title>, <author>, <year>, and <price> have text content because they contain tex

8) XML attribute

Attributes often provide information that is not a part of the data. In the example below, the file type is irrelevant to the data, but can be important to the software that wants to manipulate the element

<file type="gif">computer.gif</file>

9) What is well formed xml and valid xml

XML with correct syntax is "Well Formed" XML.

XML validated against a DTD is "Valid" XML.

10) XML DTD

<!DOCTYPE note
[
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>

11) XML Schema

<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>

12) XSLT example

<?xml version="1.0" encoding="ISO-8859-1"?>

<xsl:for-each select="breakfast_menu/food">

- <xsl:value-of select="price"/>

</div>

<xsl:value-of select="description"/>

<xsl:value-of select="calories"/> (calories per serving)

</span>

</div>

</xsl:for-each>

</body>

</html>

13) XMLHttpRequest

The XMLHttpRequest object is used to exchange data with a server behind the scenes.

The XMLHttpRequest object is a developer's dream, because you can:

Update a web page without reloading the page

Request data from a server after the page has loaded

Receive data from a server after the page has loaded

Send data to a server in the background.

14) Manipulating html using xml

<html>

<body>

<h1>W3Schools Internal Note</h1>

<div>

<b>Message:</b> <span id="message"></span>

</div>

if (window.XMLHttpRequest)

{// code for IE7+, Firefox, Chrome, Opera, Safari

xmlhttp=new XMLHttpRequest();

}

else

{// code for IE6, IE5

xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");

}

xmlhttp.open("GET","note.xml",false);

xmlhttp.send();

xmlDoc=xmlhttp.responseXML;

document.getElementById("to").innerHTML=

xmlDoc.getElementsByTagName("to")[0].childNodes[0].nodeValue;

document.getElementById("from").innerHTML=

xmlDoc.getElementsByTagName("from")[0].childNodes[0].nodeValue;

document.getElementById("message").innerHTML=

xmlDoc.getElementsByTagName("body")[0].childNodes[0].nodeValue;

</script>

</body>

</html>

Note.xml is the following

<?xml version="1.0" encoding="ISO-8859-1"?>

<note>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>

15) CDATA

Everything inside a CDATA section is ignored by the parser.
A CDATA section starts with "<![CDATA[" and ends with "]]>”

16) XPATH

Nodes

In XPath, there are seven kinds of nodes: element, attribute, text, namespace, processing-instruction, comment, and document nodes.

XML documents are treated as trees of nodes. The topmost element of the tree is called the root element.

Look at the following XML document:

<?xml version="1.0" encoding="ISO-8859-1"?>

<bookstore>
<book>
    <title lang="en">Harry Potter</title>
    <author>J K. Rowling</author>
<year>2005</year>
    <price>29.99</price>
</book>
</bookstore>

Example of nodes in the XML document above:

<bookstore> (root element node)

<author>J K. Rowling</author> (element node)

lang="en" (attribute node)

17) Selecting Nodes

nodename	Selects all child nodes of the named node
/	Selects from the root node
//	Selects nodes in the document from the current node that match the selection no matter where they are
.	Selects the current node
..	Selects the parent of the current node
@	Selects attributes

18) Xpath example

<html>

<body>

function loadXMLDoc(dname)

{

if (window.XMLHttpRequest)

{

xhttp=new XMLHttpRequest();

}

else

{

xhttp=new ActiveXObject("Microsoft.XMLHTTP");

}

xhttp.open("GET",dname,false);

xhttp.send("");

return xhttp.responseXML;

}

xml=loadXMLDoc("books.xml");

path="/bookstore/book/title"

// code for IE

if (window.ActiveXObject)

{

var nodes=xml.selectNodes(path);

for (i=0;i<nodes.length;i++)

{

document.write(nodes[i].childNodes[0].nodeValue);

document.write("<br />");

}

// code for Mozilla, Firefox, Opera, etc.

else if (document.implementation && document.implementation.createDocument)

{

var nodes=xml.evaluate(path, xml, null, XPathResult.ANY_TYPE, null);

var result=nodes.iterateNext();

while (result)

{

document.write(result.childNodes[0].nodeValue);

document.write("<br />");

result=nodes.iterateNext();

}

</script>

</body>

</html>

XML used in this example

<?xml version="1.0" encoding="ISO-8859-1"?>

<bookstore>

<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>

<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>

<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>

<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>

</bookstore>

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Saturday, February 19, 2011

XML , XSLT and XPATH Questions

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