Xml 150323102007-conversion-gate01

Notes By Niraj Bharambe
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XML Tutorial
XML stands for eXtensible Markup Language.
XML is designed to transport and store data.
XML is important to know, and very easy to learn.
XML Document Example
<?xml version="1.0"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>

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Introduction to XML
XML was designed to transport and store data.
HTML was designed to display data.
What You Should Already Know
Before you continue you should have a basic understanding of the following:
 HTML
 JavaScript
If you want to study these subjects first, find the tutorials on our Home page.
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
The Difference Between XML and HTML
XML is not a replacement for HTML.
XML and HTML were designed with different goals:
 XML was designed to transport and store data, with focus on what data is
 HTML was designed to display data, with focus on how data looks
HTML is about displaying information, while XML is about carrying information.

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XML Does Not DO Anything
Maybe it is a little hard to understand, but 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:
<note>
<to>Tove</to>
<from>Jani</from>
</note>
The note above is quite self descriptive. It has sender and receiver information, it also has a heading
and a message body.
But still, this XML document does not DO anything. It is just information wrapped in tags. Someone
must write a piece of software to send, receive or display it.
With XML You Invent Your Own Tags
The tags in the example above (like <to> and <from>) are not defined in any XML standard. These
tags are "invented" by the author of the XML document.
That is because the XML language has no predefined tags.
The tags used in HTML are predefined. HTML documents can only use tags defined in the HTML
standard (like <p>, <h1>, etc.).
XML allows the author to define his/her own tags and his/her own document structure.
XML is Not a Replacement for HTML
XML is a complement to HTML.
It is important to understand that 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.
My best description of XML is this:
XML is a software- and hardware-independent tool for carrying information.

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XML is a W3C Recommendation
XML became a W3C Recommendation on February 10, 1998.
XML is everywhere
XML is now as important for the Web as HTML was to the foundation of the Web.
XML is the most common tool for data transmissions between all sorts of applications.

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How Can XML be Used?
XML is used in many aspects of web development, often to simplify data storage and
sharing.
XML Separates Data from HTML
If you need to display dynamic data in your HTML document, it will take a lot of work to edit the HTML
each time the data changes.
With XML, data can be stored in separate XML files. This way you can concentrate on using HTML/CSS
for display and layout, and be sure that changes in the underlying data will not require any changes to
the HTML.
With a few lines of JavaScript code, you can read an external XML file and update the data content of
your web page.
XML Simplifies Data Sharing
In the real world, computer systems and databases contain data in incompatible formats.
XML data is stored in plain text format. This provides a software- and hardware-independent way of
storing data.
This makes it much easier to create data that can be shared by different applications.
XML Simplifies Data Transport
One of the most time-consuming challenges for developers is to exchange data between incompatible
systems over the Internet.
Exchanging data as XML greatly reduces this complexity, since the data can be read by different
incompatible applications.
XML Simplifies Platform Changes
Upgrading to new systems (hardware or software platforms), is always time consuming. Large
amounts of data must be converted and incompatible data is often lost.

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XML data is stored in text format. This makes it easier to expand or upgrade to new operating
systems, new applications, or new browsers, without losing data.
XML Makes Your Data More Available
Different applications can access your data, not only in HTML pages, but also from XML data sources.
With XML, your data can be available to all kinds of "reading machines" (Handheld computers, voice
machines, news feeds, etc), and make it more available for blind people, or people with other
disabilities.
XML is Used to Create New Internet Languages
A lot of new Internet languages are created with XML.
Here are some examples:
 XHTML
 WSDL for describing available web services
 WAP and WML as markup languages for handheld devices
 RSS languages for news feeds
 RDF and OWL for describing resources and ontology
 SMIL for describing multimedia for the web
If Developers Have Sense
If they DO have sense, future applications will exchange their data in XML.
The future might give us word processors, spreadsheet applications and databases that can read e ach
other's data in XML format, without any conversion utilities in between.

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XML Tree
XML documents form a tree structure that starts at "the root" and branches to "the
leaves".
An Example XML Document
XML documents use a self-describing and simple syntax:
<?xml version="1.0" encoding="ISO-8859-1"?>
<note>
<to>Tove</to>
<from>Jani</from>
</note>
The first line is the XML declaration. It defines the XML version (1.0) and the encoding used (ISO-
8859-1 = Latin-1/West European character set).
The next line describes the root element of the document (like saying: "this document is a note"):
<note>
The next 4 lines describe 4 child elements of the root (to, from, heading, and body):
<to>Tove</to>
<from>Jani</from>
And finally the last line defines the end of the root element:
</note>
You can assume, from this example, that the XML document contains a note to Tove from Jani.
Don't you agree that XML is pretty self-descriptive?
XML Documents Form a Tree Structure
XML documents must contain a root element. This element is "the parent" of all other elements.

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The elements in an XML document form a document tree. The tree starts at the root and branches to
the lowest level of the tree.
All elements can have sub elements (child elements):
<root>
<child>
<subchild>.....</subchild>
</child>
</root>
The terms parent, child, and sibling are used to describe the relationships between elements. Parent
elements have children. Children on the same level are called siblings (brothers or sisters).
All elements can have text content and attributes (just like in HTML).
Example:
The image above represents one book in the XML below:
<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>
</book>

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<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
</book>
</bookstore>
The root element in the example is <bookstore>. All <book> elements in the document are contained
within <bookstore>.
The <book> element has 4 children: <title>, < author>, <year>, <price>.

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XML Syntax Rules
The syntax rules of XML are very simple and logical. The rules are easy to learn, and
easy to use.
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.
<br>
In XML, it is illegal to omit the closing tag. All elements must have a closing tag:
<p>This is a paragraph.</p>
<br />
Note: You might have noticed from the previous example that the XML declaration did not have a
closing tag. This is not an error. The declaration is not a part of the XML document itself, and it has no
closing tag.
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>
Note: "Opening and closing tags" are often referred to as "Start and end tags". Use whatever you
prefer. It is exactly the same thing.
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:

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<b><i>This text is bold and italic</i></b>
In the example above, "Properly nested" simply means that since the <i> element is opened inside
the <b> element, it must be closed inside the <b> element.
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 rootelement.
<root>
<child>
<subchild>.....</subchild>
</child>
</root>
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.
Study the two XML documents below. The first one is incorrect, the second is correct:
<note date=12/11/2007>
<to>Tove</to>
<from>Jani</from>
</note>
<note date="12/11/2007">
<to>Tove</to>
<from>Jani</from>
</note>
The error in the first document is that the date attribute in the note element is not quoted.
Entity References
Some characters have a special meaning in XML.
If you place a character like "<" inside an XML element, it will generate an error because the parser
interprets it as the start of a new element.
This will generate an XML error:

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

White-space is Preserved in XML
HTML truncates multiple white-space characters to one single white-space:
HTML: Hello Tove
Output: Hello Tove
With XML, the white-space in a document is not truncated.
XML Stores New Line as LF
In Windows applications, a new line is normally stored as a pair of characters: carriage return (CR)
and line feed (LF). In Unix applications, a new line is normally stored as an LF character. Macintosh
applications also use an LF to store a new line. XML stores a new line as LF.

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XML Elements
An XML document contains XML Elements.
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>
</book>
<book category="WEB">
<title>Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
</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 contentbecause they contain text.
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.

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Best Naming Practices
Make names descriptive. Names with an underscore separator are nice: <first_name>, <last_name>.
Names should be short and simple, like this: <book_title> not like this: <the_title_of_the_book>.
Avoid "-" characters. If you name something "first-name," some software may think you want to
subtract name from first.
Avoid "." characters. If you name something "first.name," some software may think that "name" is a
property of the object "first."
Avoid ":" characters. Colons are reserved to be used for something called namespaces (more later).
XML documents often have a corresponding database. A good practice is to use the naming rules of
your database for the elements in the XML documents.
Non-English letters like éòá are perfectly legal in XML, but watch out for problems if your software
vendor doesn't support them.
XML Elements are Extensible
XML elements can be extended to carry more information.
Look at the following XML example:
<note>
<to>Tove</to>
<from>Jani</from>
</note>
Let's imagine that we created an application that extracted the <to>, <from>, and <body> elements
from the XML document to produce this output:
MESSAGE
To: Tove
From: Jani
Don't forget me this weekend!
Imagine that the author of the XML document added some extra information to it:

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<note>
<date>2008-01-10</date>
<to>Tove</to>
<from>Jani</from>
</note>
Should the application break or crash?
No. The application should still be able to find the <to>, <from>, and <body> elements in the XML
document and produce the same output.
One of the beauties of XML, is that it can be extended without breaking applications.

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XML Attributes
XML elements can have attributes, just like HTML.
Attributes provide additional information about an element.
XML Attributes
In HTML, attributes provide additional information about elements:
<img src="computer.gif">
<a href="demo.asp">
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>
XML Attributes Must be Quoted
Attribute values must always be quoted. Either single or double quotes can be used. For a person's
sex, the person element can be written like this:
<person sex="female">
or like this:
<person sex='female'>
If the attribute value itself contains double quotes you can use single quotes, like in this example:
<gangster name='George "Shotgun" Ziegler'>
or you can use character entities:
<gangster name="George "Shotgun" Ziegler">
XML Elements vs. Attributes
Take a look at these examples:

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<person sex="female">
<firstname>Anna</firstname>
<lastname>Smith</lastname>
</person>
<person>
<sex>female</sex>
<firstname>Anna</firstname>
<lastname>Smith</lastname>
</person>
In the first example sex is an attribute. In the last, sex is an element. Both examples provide the
same information.
There are no rules about when to use attributes or when to use elements. Attributes are handy in
HTML. In XML my advice is to avoid them. Use elements instead.
My Favorite Way
The following three XML documents contain exactly the same information:
A date attribute is used in the first example:
<note date="10/01/2008">
<to>Tove</to>
<from>Jani</from>
</note>
A date element is used in the second example:
<note>
<date>10/01/2008</date>
<to>Tove</to>
<from>Jani</from>
</note>
An expanded date element is used in the third: (THIS IS MY FAVORITE):
<note>
<date>
<day>10</day>
<month>01</month>
<year>2008</year>
</date>
<to>Tove</to>
<from>Jani</from>

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</note>
Avoid XML Attributes?
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.
Don't end up like this:
<note day="10" month="01" year="2008"
to="Tove" from="Jani" heading="Reminder"
body="Don't forget me this weekend!">
</note>
XML Attributes for Metadata
Sometimes ID references are assigned to elements. These IDs can be used to identify XML elements in
much the same way as the id attribute in HTML. This example demonstrates this:
<messages>
<note id="501">
<to>Tove</to>
<from>Jani</from>
</note>
<note id="502">
<to>Jani</to>
<from>Tove</from>
<heading>Re: Reminder</heading>
<body>I will not</body>
</note>
</messages>
The id attributes above are for identifying the different notes. It is not a part of the note itself.
What I'm trying to say here is that metadata (data about data) should be stored as attributes, and the
data itself should be stored as elements.

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XML Validation
XML with correct syntax is "Well Formed" XML.
XML validated against a DTD is "Valid" XML.
Well Formed XML Documents
A "Well Formed" XML document has correct XML syntax.
The syntax rules were described in the previous chapters:
 XML documents must have a root element
 XML elements must have a closing tag
 XML tags are case sensitive
 XML elements must be properly nested
 XML attribute values must be quoted
<note>
<to>Tove</to>
<from>Jani</from>
</note>
Valid XML Documents
A "Valid" XML document is a "Well Formed" XML document, which also conforms to the rules of a
Document Type Definition (DTD):
<!DOCTYPE note SYSTEM "Note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
</note>
The DOCTYPE declaration, in the example above, is a reference to an external DTD file. The content of
the file is shown in the paragraph below.

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XML DTD
The purpose of a DTD is to define the structure of an XML document. It defines the structure with a
list of legal elements:
<!DOCTYPE note
[
<!ELEMENT note (to,from,heading,body)>
<!ELEMENT to (#PCDATA)>
<!ELEMENT from (#PCDATA)>
<!ELEMENT heading (#PCDATA)>
<!ELEMENT body (#PCDATA)>
]>
If you want to study DTD, you will find our DTD tutorial on our homepage.
XML Schema
W3C supports an XML-based alternative to DTD, called 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>
If you want to study XML Schema, you will find our Schema tutorial on our homepage.
A General XML Validator
To help you check the syntax of your XML files, we have created an XML validator to syntax-check
your XML.
Please see the next chapter.

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XML Validator
Use our XML validator to syntax-check your XML.
XML Errors Will Stop You
Errors in XML documents will stop your XML applications.
The W3C XML specification states that a program should stop processing an XML document if it finds
an error. The reason is that XML software should be small, fast, and compatible.
HTML browsers will display documents with errors (like missing end tags). HTML browsers are big and
incompatible because they have a lot of unnecessary code to deal with (and display) HTML errors.
With XML, errors are not allowed.
Syntax-Check Your XML
To help you syntax-check your XML, we have created an XML validator.
Paste your XML into the text area below, and syntax-check it by clicking the "Validate" button.
<?xml version="1.0" ?>
<note>
<to>Tove</to>
<from>Jani</Ffrom>
<body>Don't forget me this w eekend!</body>
</note>
Note: This only checks if your XML is "Well formed". If you want to validate your XML against a DTD,
see the last paragraph on this page.
Syntax-Check an XML File
You can syntax-check an XML file by typing the URL of the file into the input field below, and then click
the "Validate" button:

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Filename:
http://w w w .w 3schools.com/xml/note_error.xml
Validate
Note: If you get an "Access denied" error, it's because your browser security does not allow file
access across domains.
The file "note_error.xml" demonstrates your browsers error handling. If you want to see an error free
message, substitute the "note_error.xml" with "cd_catalog.xml".
Validate Your XML Against a DTD
If you run Internet Explorer, you can validate your XML against a DTD in the text area below.
Just add the DOCTYPE declaration (with the DTD) after the <xml> element, and click the "Validate"
button:
<?xml version="1.0" ?>
<!DOCTYPEnote [
<!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>
<message>Don't forget me this w eekend!</message>
</note>

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Viewing XML Files
Raw XML files can be viewed in all major browsers.
Don't expect XML files to be displayed as HTML pages.
Viewing XML Files
- <note>
<to>Tove</to>
<from>Jani</from>
</note>
Look at this XML file: note.xml
The XML document will be displayed with color-coded root and child elements. A plus (+) or minus
sign (-) to the left of the elements can be clicked to expand or collapse the element structure. To view
the raw XML source (without the + and - signs), select "View Page Source" or "View Source" from the
browser menu.
Note: In Safari, only the element text will be displayed. To view the raw XML, you must right click the
page and select "View Source"
Viewing an Invalid XML File
If an erroneous XML file is opened, the browser will report the error.
Look at this XML file: note_error.xml
Other XML Examples
Viewing some XML documents will help you get the XML feeling.
An XML CD catalog
This is a CD collection, stored as XML data.

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An XML plant catalog
This is a plant catalog from a plant shop, stored as XML data.
A Simple Food Menu
This is a breakfast food menu from a restaurant, stored as XML data.
Why Does XML Display Like This?
XML documents do not carry information about how to display the data.
Since XML tags are "invented" by the author of the XML document, browsers do not know if a tag like
<table> describes an HTML table or a dining table.
Without any information about how to display the data, most browsers will just display the XML
document as it is.
In the next chapters, we will look at different solutions for the display problem, using CSS, XSLT, and
JavaScript.

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Displaying XML with CSS
With CSS (Cascading Style Sheets) you can add display information to an XML
document.
Displaying your XML Files with CSS?
It is possible to use CSS to format an XML document.
Below is an example of how to use a CSS style sheet to format an XML document:
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
Below is a fraction of the XML file. The second line links the XML file to the CSS file:
<?xml-stylesheet type="text/css" href="cd_catalog.css"?>
<CATALOG>
<CD>
<TITLE>Empire Burlesque</TITLE>
<ARTIST>Bob Dylan</ARTIST>
<COUNTRY>USA</COUNTRY>
<COMPANY>Columbia</COMPANY>
<PRICE>10.90</PRICE>
<YEAR>1985</YEAR>
</CD>
<CD>
<TITLE>Hide your heart</TITLE>
<ARTIST>Bonnie Tyler</ARTIST>
<COUNTRY>UK</COUNTRY>
<COMPANY>CBS Records</COMPANY>
<PRICE>9.90</PRICE>
<YEAR>1988</YEAR>
</CD>
.
.
.
</CATALOG>
Formatting XML with CSS is not the most common method.
W3C recommends using XSLT instead. See the next chapter.

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Displaying XML with XSLT
With XSLT you can transform an XML document into HTML.
Displaying XML with XSLT
XSLT is the recommended style sheet language of XML.
XSLT (eXtensible Stylesheet Language Transformations) is far more sophisticated than CSS.
XSLT can be used to transform XML into HTML, before it is displayed by a browser:
Display XML with XSLT
If you want to learn more about XSLT, find our XSLT tutorial on our homepage.
Transforming XML with XSLT on the Server
In the example above, the XSLT transformation is done by the browser, when the browser reads the
XML file.
Different browsers may produce different results when transforming XML with XSLT. To reduce this
problem the XSLT transformation can be done on the server.

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The XMLHttpRequest Object
The XMLHttpRequest Object
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
To learn more about the XMLHttpRequest object, study our XML DOM tutorial.
XMLHttpRequest Example
When you type a character in the input field below, an XMLHttpRequest is sent to the server - and
name suggestions are returned (from a file on the server):
Type a letter in the input box:
First Name
Suggestions:
Create an XMLHttpRequest Object
All modern browsers (IE7+, Firefox, Chrome, Safari, and Opera) have a built-in XMLHttpRequest
object.
Syntax for creating an XMLHttpRequest object:
xmlhttp=new XMLHttpRequest();
Old versions of Internet Explorer (IE5 and IE6) use an ActiveX Object:
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); In the next chapter, we will use the
XMLHttpRequest object to retrieve XML information from a server.

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XML Parser
All modern browsers have a built-in XML parser.
An XML parser converts an XML document into an XML DOM object - which can then be
manipulated with JavaScript.
Parse an XML Document
The following code fragment parses an XML document into an XML DOM object:
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.open("GET","books.xml",false);
xmlhttp.send();
xmlDoc=xmlhttp.responseXML;
Parse an XML String
The following code fragment parses an XML string into an XML DOM object:
txt="<bookstore><book>";
txt=txt+"<title>Everyday Italian</title>";
txt=txt+"<author>Giada De Laurentiis</author>";
txt=txt+"<year>2005</year>";
txt=txt+"</book></bookstore>";
if (window.DOMParser)
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(txt,"text/xml");
}
else // Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.loadXML(txt);
}

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Note: Internet Explorer uses the loadXML() method to parse an XML string, while other browsers use
the DOMParser object.
Access Across Domains
For security reasons, modern browsers do not allow access across domains.
This means, that both the web page and the XML file it tries to load, must be located on the same
server.
The XML DOM
In the next chapter you will learn how to access and retrieve data from the XML DOM object.

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XML DOM
A DOM (Document Object Model) defines a standard way for accessing and
manipulating documents.
The XML DOM
The XML DOM defines a standard way for accessing and manipulating XML documents.
The XML DOM views an XML document as a tree-structure.
All elements can be accessed through the DOM tree. Their content (text and attributes) can be
modified or deleted, and new elements can be created. The elements, their text, and their attributes
are all known as nodes.
You can learn more about the XML DOM in our XML DOM tutorial.
The HTML DOM
The HTML DOM defines a standard way for accessing and manipulating HTML documents.
All HTML elements can be accessed through the HTML DOM.
You can learn more about the HTML DOM in our HTML DOM tutorial.
Load an XML File - Cross-browser Example
The following example parses an XML document ("note.xml") into an XML DOM object and then
extracts some info from it with a JavaScript:
Example
<html>
<body>
<h1>W3Schools Internal Note</h1>
<div>
<b>To:</b> <span id="to"></span><br />
<b>From:</b> <span id="from"></span><br />
<b>Message:</b> <span id="message"></span>
</div>
<script>

31
}
else
}
xmlhttp.open("GET","note.xml",false);
xmlhttp.send();
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>
Try it yourself »
Important Note!
To extract the text "Tove" from the <to> element in the XML file above ("note.xml"), the syntax is:
getElementsByTagName("to")[0].childNodes[0].nodeValue
Notice that even if the XML file contains only ONE <to> element you still have to specify the array
index [0]. This is because the getElementsByTagName() method returns an array.
Load an XML String - Cross-browser Example
The following example parses an XML string into an XML DOM object and then extracts some info from
it with a JavaScript:
Example
<html>
<body>
<h1>W3Schools Internal Note</h1>
<div>
<b>To:</b> <span id="to"></span><br />
<b>From:</b> <span id="from"></span><br />
<b>Message:</b> <span id="message"></span>
</div>

32
<script>
txt="<note>";
txt=txt+"<to>Tove</to>";
txt=txt+"<from>Jani</from>";
txt=txt+"<heading>Reminder</heading>";
txt=txt+"<body>Don't forget me this weekend!</body>";
txt=txt+"</note>";
if (window.DOMParser)
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(txt,"text/xml");
}
else // Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.loadXML(txt);
}
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>

33
XML in HTML
Display XML Data in an HTML Page
In the following example, we open an XML file ("cd_catalog.xml"), then we loop through each CD
element, and display the value of the ARTIST element and the TITLE element in an HTML table:
Example
<html>
<body>
<script>
}
else
}
xmlhttp.open("GET","cd_catalog.xml",false);
xmlhttp.send();
document.write("<table border='1'>");
var x=xmlDoc.getElementsByTagName("CD");
for (i=0;i<x.length;i++)
{
document.write("<tr><td>");
document.write(x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue
);
document.write("</td><td>");
document.write(x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue)
;
document.write("</td></tr>");
}
document.write("</table>");
</script>
</body>
</html>

34
XML Applications
This chapter demonstrates some small XML applications built on XML, HTML, XML DOM
and JavaScript.
The XML Document Used
In this application we will use the "cd_catalog.xml" file.
Display the First CD in an HTML div Element
The following example gets the XML data from the first CD element and displays it in an HTML element
with id="showCD". The displayCD() function is called when the page is loaded:
Example
x=xmlDoc.getElementsByTagName("CD");
i=0;
function displayCD()
{
artist=(x[i].getElementsByTagName("ARTIST")[0].childNodes[0].nodeValue);
title=(x[i].getElementsByTagName("TITLE")[0].childNodes[0].nodeValue);
year=(x[i].getElementsByTagName("YEAR")[0].childNodes[0].nodeValue);
txt="Artist: " + artist + "<br />Title: " + title + "<br />Year: "+ year;
document.getElementById("showCD").innerHTML=txt;
}
Try it yourself »
Navigate Between the CDs
To navigate between the CDs, in the example above, add a next() and previous() function:
Example
function next()
{ // display the next CD, unless you are on the last CD
if (i<x.length-1)
{
i++;
displayCD();
}

35
}
function previous()
{ // displays the previous CD, unless you are on the first CD
if (i>0)
{
i--;
displayCD();
}
}
Try it yourself »

36
XML Namespaces
XML Namespaces provide a method to avoid element name conflicts.
Name Conflicts
In XML, element names are defined by the developer. This often results in a conflict when trying to
mix XML documents from different XML applications.
This XML carries HTML table information:
<table>
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>
This XML carries information about a table (a piece of furniture):
<table>
<name>African Coffee Table</name>
<width>80</width>
<length>120</length>
</table>
If these XML fragments were added together, there would be a name conflict. Both contain a <table>
element, but the elements have different content and meaning.
An XML parser will not know how to handle these differences.
Solving the Name Conflict Using a Prefix
Name conflicts in XML can easily be avoided using a name prefix.
This XML carries information about an HTML table, and a piece of furniture:
<h:table>
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
<f:table>

37
<f:name>African Coffee Table</f:name>
<f:width>80</f:width>
<f:length>120</f:length>
</f:table>
In the example above, there will be no conflict because the two <table> elements have different
names.
XML Namespaces - The xmlns Attribute
When using prefixes in XML, a so-called namespace for the prefix must be defined.
The namespace is defined by the xmlns attribute in the start tag of an element.
The namespace declaration has the following syntax. xmlns:prefix="URI".
<root>
<h:table xmlns:h="http://www.w3.org/TR/html4/">
<h:tr>
<h:td>Apples</h:td>
</h:tr>
</h:table>
<f:table xmlns:f="http://www.w3schools.com/furniture">
</f:table>
</root>
In the example above, the xmlns attribute in the <table> tag give the h: and f: prefixes a qualified
namespace.
When a namespace is defined for an element, all child elements with the same prefix are associated
with the same namespace.
Namespaces can be declared in the elements where they are used or in the XML root element:
<root xmlns:h="http://www.w3.org/TR/html4/"
xmlns:f="http://www.w3schools.com/furniture">
<h:table>
<h:tr>
<h:td>Apples</h:td>
</h:tr>
</h:table>

38
<f:table>
</f:table>
</root>
Note: The namespace URI is not used by the parser to look up information.
The purpose is to give the namespace a unique name. However, often companies use the namespace
as a pointer to a web page containing namespace information.
Try to go to http://www.w3.org/TR/html4/.
Uniform Resource Identifier (URI)
A Uniform Resource Identifier (URI) is a string of characters which identifies an Internet Resource.
The most common URI is the Uniform Resource Locator (URL) which identifies an Internet domain
address. Another, not so common type of URI is the Universal Resource Name (URN).
In our examples we will only use URLs.
Default Namespaces
Defining a default namespace for an element saves us from using prefixes in all the child elements. It
has the following syntax:
xmlns="namespaceURI"
This XML carries HTML table information:
<table xmlns="http://www.w3.org/TR/html4/">
<tr>
<td>Apples</td>
<td>Bananas</td>
</tr>
</table>
This XML carries information about a piece of furniture:
<table xmlns="http://www.w3schools.com/furniture">
<name>African Coffee Table</name>
<width>80</width>
<length>120</length>
</table>

39
Namespaces in Real Use
XSLT is an XML language that can be used to transform XML documents into other formats, like HTML.
In the XSLT document below, you can see that most of the tags are HTML tags.
The tags that are not HTML tags have the prefix xsl, identified by the namespace
xmlns:xsl="http://www.w3.org/1999/XSL/Transform":
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<html>
<body>
<h2>My CD Collection</h2>
<table border="1">
<tr>
<th align="left">Title</th>
<th align="left">Artist</th>
</tr>
<xsl:for-each select="catalog/cd">
<tr>
<td><xsl:value-of select="title"/></td>
<td><xsl:value-of select="artist"/></td>
</tr>
</xsl:for-each>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

40
XML CDATA
All text in an XML document will be parsed by the parser.
But text inside a CDATA section will be ignored by the parser.
PCDATA - Parsed Character Data
XML parsers normally parse all the text in an XML document.
When an XML element is parsed, the text between the XML tags is also parsed:
<message>This text is also parsed</message>
The parser does this because XML elements can contain other elements, as in this example, where the
<name> element contains two other elements (first and last):
<name><first>Bill</first><last>Gates</last></name>
and the parser will break it up into sub-elements like this:
<name>
<first>Bill</first>
<last>Gates</last>
</name>
Parsed Character Data (PCDATA) is a term used about text data that will be parsed by the XML parser.
CDATA - (Unparsed) Character Data
The term CDATA is used about text data that should not be parsed by the XML parser.
Characters like "<" and "&" are illegal in XML elements.
"<" will generate an error because the parser interprets it as the start of a new element.
"&" will generate an error because the parser interprets it as the start of an character entity.
Some text, like JavaScript code, contains a lot of "<" or "&" characters. To avoid errors script code can
be defined as CDATA.
Everything inside a CDATA section is ignored by the parser.

41
A CDATA section starts with "<![CDATA[" and ends with "]]>":
<script>
<![CDATA[
function matchwo(a,b)
{
if (a < b && a < 0) then
{
return 1;
}
else
{
return 0;
}
}
]]>
</script>
In the example above, everything inside the CDATA section is ignored by the parser.
Notes on CDATA sections:
A CDATA section cannot contain the string "]]>". Nested CDATA sections are not allowed.
The "]]>" that marks the end of the CDATA section cannot contain spaces or line breaks.

42
XML Encoding
XML documents can contain non ASCII characters, like Norwegian æ ø å , or French ê è
é.
To avoid errors, specify the XML encoding, or save XML files as Unicode.
XML Encoding Errors
If you load an XML document, you can get two different errors indicating encoding problems:
An invalid character was found in text content.
You get this error if your XML contains non ASCII characters, and the file was saved as single-byte
ANSI (or ASCII) with no encoding specified.
Single byte XML file with encoding attribute.
Same single byte XML file with no encoding attribute.
Switch from current encoding to specified encoding not supported.
You get this error if your XML file was saved as double-byte Unicode (or UTF-16) with a single-byte
encoding (Windows-1252, ISO-8859-1, UTF-8) specified.
You also get this error if your XML file was saved with single-byte ANSI (or ASCII), with double-byte
encoding (UTF-16) specified.
Double byte XML file without encoding.
Same double byte XML file with single byte encoding.
Windows Notepad
Windows Notepad save files as single-byte ANSI (ASCII) by default.
If you select "Save as...", you can specify ANSI, UTF-8, Unicode(UTF-16), or Unicode Big.
Experiment with the XML below (without any coding attribute), and save it as ANSI, UTF-8, and
Unicode.

43
<?xml version="1.0"?>
<note>
<from>Jani</from>
<to>Tove</to>
<message>Norwegian: æøå. French: êèé</message>
</note>
Try to drag the files into your browser, ands see the result. Different browsers will display different
results.
Experiment with different encodings:
<?xml version="1.0" encoding="us-ascii"?>
<?xml version="1.0" encoding="windows-1252"?>
<?xml version="1.0" encoding="UTF-8"?>
<?xml version="1.0" encoding="UTF-16"?>
Try these:
Note saved with right encoding
Note saved with wrong encoding
Conclusion
 Always use the encoding attribute
 Use an editor that supports encoding
 Make sure you know what encoding the editor uses
 Use the same encoding in your encoding attribute

44
XML on the Server
XML files are plain text files just like HTML files.
XML can easily be stored and generated by a standard web server.
Storing XML Files on the Server
XML files can be stored on an Internet server exactly the same way as HTML files.
Start Windows Notepad and write the following lines:
<note>
<from>Jani</from>
<to>Tove</to>
<message>Remember me this weekend</message>
</note>
Save the file on your web server with a proper name like "note.xml".
Generating XML with ASP
XML can be generated on a server without any installed XML software.
To generate an XML response from the server - simply write the following code and save it as an ASP
file on the web server:
<%
response.ContentType="text/xml"
response.Write("<?xml version='1.0' encoding='ISO-8859-1'?>")
response.Write("<note>")
response.Write("<from>Jani</from>")
response.Write("<to>Tove</to>")
response.Write("<message>Remember me this weekend</message>")
response.Write("</note>")
%>
Note that the content type of the response must be set to "text/xml".
See how the ASP file will be returned from the server.
If you want to study ASP, you will find our ASP tutorial on our homepage.

45
Generating XML with PHP
To generate an XML response from the server using PHP, use following code:
<?php
header("Content-type: text/xml");
echo "<?xml version='1.0' encoding='ISO-8859-1'?>";
echo "<note>";
echo "<from>Jani</from>";
echo "<to>Tove</to>";
echo "<message>Remember me this weekend</message>";
echo "</note>";
?>
Note that the content type of the response header must be set to "text/xml".
See how the PHP file will be returned from the server.
If you want to study PHP, you will find our PHP tutorial on our homepage.
Generating XML From a Database
XML can be generated from a database without any installed XML software.
To generate an XML database response from the server, simply write the following code and save it as
an ASP file on the web server:
<%
response.ContentType = "text/xml"
set conn=Server.CreateObject("ADODB.Connection")
conn.provider="Microsoft.Jet.OLEDB.4.0;"
conn.open server.mappath("/db/database.mdb")
sql="select fname,lname from tblGuestBook"
set rs=Conn.Execute(sql)
response.write("<?xml version='1.0' encoding='ISO-8859-1'?>")
response.write("<guestbook>")
while (not rs.EOF)
response.write("<guest>")
response.write("<fname>" & rs("fname") & "</fname>")
response.write("<lname>" & rs("lname") & "</lname>")
response.write("</guest>")
rs.MoveNext()
wend
rs.close()
conn.close()

46
response.write("</guestbook>")
%>
See the real life database output from the ASP file above.
The example above uses ASP with ADO.
If you want to study ASP and ADO, you will find the tutorials on our homepage.
Transforming XML with XSLT on the Server
This ASP transforms an XML file to XHTML on the server:
<%
'Load XML
set xml = Server.CreateObject("Microsoft.XMLDOM")
xml.async = false
xml.load(Server.MapPath("simple.xml"))
'Load XSL
set xsl = Server.CreateObject("Microsoft.XMLDOM")
xsl.async = false
xsl.load(Server.MapPath("simple.xsl"))
'Transform file
Response.Write(xml.transformNode(xsl))
%>
Example explained
 The first block of code creates an instance of the Microsoft XML parser (XMLDOM), and loads
the XML file into memory.
 The second block of code creates another instance of the parser and loads the XSL file into
memory.
 The last line of code transforms the XML document using the XSL document, and sends the
result as XHTML to your browser. Nice!
See how it works.
Saving XML To a File Using ASP
This ASP example creates a simple XML document and saves it on the server:
<%
text="<note>"
text=text & "<to>Tove</to>"
text=text & "<from>Jani</from>"
text=text & "<heading>Reminder</heading>"

47
text=text & "<body>Don't forget me this weekend!</body>"
text=text & "</note>"
set xmlDoc=Server.CreateObject("Microsoft.XMLDOM")
xmlDoc.async=false
xmlDoc.loadXML(text)
xmlDoc.Save("test.xml")
%>

48
XML DOM Advanced
The XML DOM - Advanced
In an earlier chapter of this tutorial we introduced the XML DOM, and we used the
getElementsByTagName() method to retrieve data from an XML document.
In this chapter we will explain some other important XML DOM methods.
You can learn more about the XML DOM in our XML DOM tutorial.
Get the Value of an Element
The XML file used in the examples below: books.xml.
The following example retrieves the text value of the first <title> element:
Example
txt=xmlDoc.getElementsByTagName("title")[0].childNodes[0].nodeValue;
Try it yourself »
Get the Value of an Attribute
The following example retrieves the text value of the "lang" attribute of the first <title> element:
Example
txt=xmlDoc.getElementsByTagName("title")[0].getAttribute("lang");
Try it yourself »
Change the Value of an Element
The following example changes the text value of the first <title> element:
Example
x=xmlDoc.getElementsByTagName("title")[0].childNodes[0];
x.nodeValue="Easy Cooking";

49
Try it yourself »
Create a New Attribute
The XML DOM setAttribute() method can be used to change the value of an existing attribute, or to
create a new attribute.
The following example adds a new attribute (edition="first") to each <book> element:
Example
x=xmlDoc.getElementsByTagName("book");
for(i=0;i<x.length;i++)
{
x[i].setAttribute("edition","first");
}
Try it yourself »
Create an Element
The XML DOM createElement() method creates a new element node.
The XML DOM createTextNode() method creates a new text node.
The XML DOM appendChild() method adds a child node to a node (after the last child).
To create a new element with text content, it is necessary to both create a new element node and a
new text node, and then append it to an existing node.
The following example creates a new element (<edition>), with the following text: First, and adds it to
the first <book> element:
Example
newel=xmlDoc.createElement("edition");
newtext=xmlDoc.createTextNode("First");
newel.appendChild(newtext);
x=xmlDoc.getElementsByTagName("book");
x[0].appendChild(newel);
Try it yourself »
Example explained:

50
 Create an <edition> element
 Create a text node with the following text: First
 Append the text node to the new <edition> element
 Append the <edition> element to the first <book> element
Remove an Element
The following example removes the first node in the first <book> element:
Example
x=xmlDoc.getElementsByTagName("book")[0];
x.removeChild(x.childNodes[0]);

51
XML Don't
Here are some technologies you should try to avoid when using XML.
Internet Explorer - XML Data Islands
What is it? An XML data island is XML data embedded into an HTML page.
Why avoid it? XML Data Islands only works with Internet Explorer browsers.
What to use instead? You should use JavaScript and XML DOM to parse and display XML in HTML.
For more information about JavaScript and XML DOM, visit our XML DOM tutorial.
XML Data Island Example
This example uses the XML document "cd_catalog.xml".
Bind the XML document to an <xml> tag in the HTML document. The id attribute defines an id for the
data island, and the src attribute points to the XML file:
Example
This example only works in IE
<html>
<body>
<xml id="cdcat" src="cd_catalog.xml"></xml>
<table border="1" datasrc="#cdcat">
<tr>
<td><span datafld="ARTIST"></span></td>
<td><span datafld="TITLE"></span></td>
</tr>
</table>
</body>
</html>
Try it yourself »
The datasrc attribute of the <table> tag binds the HTML table to the XML data island.

52
The <span> tags allow the datafld attribute to refer to the XML element to be displayed. In this case,
"ARTIST" and "TITLE". As the XML is read, additional rows are created for each <CD> element.
Internet Explorer - Behaviors
What is it? Internet Explorer 5 introduced behaviors. Behaviors are a way to add behaviors to XML
(or HTML) elements with the use of CSS styles.
Why avoid it? The behavior attribute is only supported by Internet Explorer.
What to use instead? Use JavaScript and XML DOM (or HTML DOM) instead.
Example 1 - Mouseover Highlight
The following HTML file has a <style> element that defines a behavior for the <h1> element:
<html>
<head>
<style type="text/css">
h1 { behavior: url(behave.htc) }
</style>
</head>
<body>
<h1>Mouse over me!!!</h1>
</body>
</html>
The XML document "behave.htc" is shown below (The file contains a JavaScript and event handlers for
the elements):
<attach for="element" event="onmouseover" handler="hig_lite" />
<attach for="element" event="onmouseout" handler="low_lite" />
<script>
function hig_lite()
{
element.style.color='red';
}
function low_lite()
{
element.style.color='blue';
}
</script>
Try it yourself »
Example 2 - Typewriter Simulation

53
The following HTML file has a <style> element that defines a behavior for elements with an id of
"typing":
<html>
<head>
<style type="text/css">
#typing
{
behavior:url(typing.htc);
font-family:'courier new';
}
</style>
</head>
<body>
<span id="typing" speed="100">IE5 introduced DHTML behaviors.
Behaviors are a way to add DHTML functionality to HTML elements
with the ease of CSS.<br /><br />How do behaviors work?<br />
By using XML we can link behaviors to any element in a web page
and manipulate that element.</p>v </span>
</body>
</html>
The XML document "typing.htc" is shown below:
<attach for="window" event="onload" handler="beginTyping" />
<method name="type" />
<script>
var i,text1,text2,textLength,t;
function beginTyping()
{
i=0;
text1=element.innerText;
textLength=text1.length;
element.innerText="";
text2="";
t=window.setInterval(element.id+".type()",speed);
}
function type()
{
text2=text2+text1.substring(i,i+1);
element.innerText=text2;
i=i+1;
if (i==textLength)
{
clearInterval(t);
}
}
</script>
Try it yourself »

54
XML Related Technologies
Below is a list of XML technologies.
XHTML (Extensible HTML)
A stricter and cleaner XML based version of HTML.
XML DOM (XML Document Object Model)
A standard document model for accessing and manipulating XML.
XSL (Extensible Style Sheet Language) XSL consists of three parts:
 XSLT (XSL Transform) - transforms XML into other formats, like HTML
 XSL-FO (XSL Formatting Objects)- for formatting XML to screen, paper, etc
 XPath - a language for navigating XML documents
XQuery (XML Query Language)
An XML based language for querying XML data.
DTD (Document Type Definition)
A standard for defining the legal elements in an XML document.
XSD (XML Schema)
An XML-based alternative to DTD.
XLink (XML Linking Language)
A language for creating hyperlinks in XML documents.
XPointer (XML Pointer Language)
Allows the XLink hyperlinks to point to more specific parts in the XML document.
SOAP (Simple Object Access Protocol)
An XML-based protocol to let applications exchange information over HTTP.
WSDL (Web Services Description Language)
An XML-based language for describing web services.
RDF (Resource Description Framework)
An XML-based language for describing web resources.
RSS (Really Simple Syndication)
A format for syndicating news and the content of news-like sites.
SVG (Scalable Vector Graphics)
Defines graphics in XML format.

55
XML in Real Life
Some examples of how XML can be used to exchange information.
Example: XML News
XMLNews is a specification for exchanging news and other information.
Using such a standard makes it easier for both news producers and news consumers to produce,
receive, and archive any kind of news information across different hardware, software, and
programming languages.
An example XMLNews document:
<nitf>
<head>
<title>Colombia Earthquake</title>
</head>
<body>
<headline>
<hl1>143 Dead in Colombia Earthquake</hl1>
</headline>
<byline>
<bytag>By Jared Kotler, Associated Press Writer</bytag>
</byline>
<dateline>
<location>Bogota, Colombia</location>
<date>Monday January 25 1999 7:28 ET</date>
</dateline>
</body>
</nitf>
Example: XML Weather Service
An example of an XML national weather service from NOAA (National Oceanic and Atmospheric
Administration):
<?xml version="1.0" encoding="ISO-8859-1" ?>
<current_observation>
<credit>NOAA's National Weather Service</credit>
<credit_URL>http://weather.gov/</credit_URL>
<image>
<url>http://weather.gov/images/xml_logo.gif</url>

56
<title>NOAA's National Weather Service</title>
<link>http://weather.gov</link>
</image>
<location>New York/John F. Kennedy Intl Airport, NY</location>
<station_id>KJFK</station_id>
<latitude>40.66</latitude>
<longitude>-73.78</longitude>
<observation_time_rfc822>Mon, 11 Feb 2008 06:51:00 -0500 EST
</observation_time_rfc822>
<weather>A Few Clouds</weather>
<temp_f>11</temp_f>
<temp_c>-12</temp_c>
<relative_humidity>36</relative_humidity>
<wind_dir>West</wind_dir>
<wind_degrees>280</wind_degrees>
<wind_mph>18.4</wind_mph>
<wind_gust_mph>29</wind_gust_mph>
<pressure_mb>1023.6</pressure_mb>
<pressure_in>30.23</pressure_in>
<dewpoint_f>-11</dewpoint_f>
<dewpoint_c>-24</dewpoint_c>
<windchill_f>-7</windchill_f>
<windchill_c>-22</windchill_c>
<visibility_mi>10.00</visibility_mi>
<icon_url_base>http://weather.gov/weather/images/fcicons/</icon_url_base>
<icon_url_name>nfew.jpg</icon_url_name>
<disclaimer_url>http://weather.gov/disclaimer.html</disclaimer_url>
<copyright_url>http://weather.gov/disclaimer.html</copyright_url>
</current_observation>

57
XML Editors
If you are serious about XML, you will benefit from using a professional XML Editor.
XML is Text-based
XML is a text-based markup language.
One great thing about XML is that XML files can be created and edited using a simple text-editor like
Notepad.
However, when you start working with XML, you will soon find that it is better to edit XML documents
using a professional XML editor.
Why Not Notepad?
Many web developers use Notepad to edit both HTML and XML documents because Notepad is included
with the most common OS and it is simple to use. Personally I often use Notepad for quick editing of
simple HTML, CSS, and XML files.
But, if you use Notepad for XML editing, you will soon run into problems.
Notepad does not know that you are writing XML, so it will not be able to assist you.
Why an XML Editor?
Today XML is an important technology, and development projects use XML-based technologies like:
 XML Schema to define XML structures and data types
 XSLT to transform XML data
 SOAP to exchange XML data between applications
 WSDL to describe web services
 RDF to describe web resources
 XPath and XQuery to access XML data
 SMIL to define graphics
To be able to write error-free XML documents, you will need an intelligent XML editor!

58
XML Editors
Professional XML editors will help you to write error-free XML documents, validate your XML against a
DTD or a schema, and force you to stick to a valid XML structure.
An XML editor should be able to:
 Add closing tags to your opening tags automatically
 Force you to write valid XML
 Verify your XML against a DTD
 Verify your XML against a Schema
 Color code your XML syntax
we have been using XMLSpy for many years. XMLSpy is our favorite XML editor. These are some of
the features we especially like:
 Available in 32-bit and 64-bit versions
 Easy to use
 Context-sensitive entry helpers
 Syntax coloring and pretty printing
 Smart Fix validation with auto-correction of errors
 Easy switching between text view and grid view
 Graphical XML Schema editor
 Database import and export for all major databases
 SharePoint® Server support
 Built in templates for many XML document types
 Chart creation for displaying XML data
 Intelligent XPath 1.0/2.0 auto-completion
 XSLT 1.0/2.0 editor, profiler, and debugger
 XQuery editor, profiler, and debugger
 SOAP client and debugger
 Graphical WSDL 1.1/2.0 editor
 XBRL validation & taxonomy editing
 Support for Office 2007 / OOXML
 Code generation in Java, C++, and C#
 HTML5 and CSS3 support

59
XML - E4X
E4X adds direct support for XML to JavaScript.
E4X Example
var employees=
<employees>
<person>
<name>Tove</name>
<age>32</age>
</person>
<person>
<name>Jani</name>
<age>26</age>
</person>
</employees>;
document.write(employees.person.(name == "Tove").age);
This example works in Firefox only!
Try it yourself »
XML As a JavaScript Object
E4X is an official JavaScript standard that adds direct support for XML.
With E4X, you can declare an XML object variable the same way as you declare a Date or an Array
object variable:
var x = new XML()
var y = new Date()
var z = new Array()
E4X is an ECMAScript (JavaScript) Standard
ECMAScript is the official name for JavaScript. ECMA-262 (JavaScript 1.3) was standardized in
December 1999.

60
E4X is an extension of JavaScript that adds direct support for XML. ECMA-357 (E4X) was standardized
in June 2004.
The ECMA organization (founded in 1961) is dedicated to the standardization of Information and
Communication Technology (ICT) and Consumer Electronics (CE). ECMA has developed standards for:
 JavaScript
 C# Language
 International Character Sets
 Optical Disks
 Magnetic Tapes
 Data Compression
 Data Communication
 and much more...
Without E4X
The following example is a cross browser example that loads an existing XML document ("note.xml")
into the XML parser and displays the message from the note:
Example
var xmlDoc;
//code for Internet Explorer
if (window.ActiveXObject)
{
xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async=false;
xmlDoc.load("note.xml");
displaymessage();
}
// code for Mozilla, Firefox, etc.
else (document.implementation && document.implementation.createDocument)
{
xmlDoc= document.implementation.createDocument("","",null);
xmlDoc.onload=displaymessage;
}
function displaymessage()
{
document.write(xmlDoc.getElementsByTagName("body")[0].firstChild.nodeValue);
}
Try it yourself »

61
With E4X
The following example is the same as above but using E4X:
var xmlDoc=new XML();
document.write(xmlDoc.body);
Much simpler, isn't it?
Browser Support
Firefox is currently the only browser with relatively good support for E4X.
There are currently no support for E4X in Opera, Chrome, or Safari.
So far there is no indication for of E4X support in Internet Explorer.
The Future of E4X
E4X is not widely supported. Maybe it offers too little practical functionality not already covered by
other solutions:
 For full XML processing, you still need the XML DOM and XPath
 For accessing XMLHttpRequests, JSON is the preferred format.
 For easy document handling, JQuery selectors are easier.

62
XML Summary. What is Next?
 XML Summary
 XML can be used to exchange, share, and store data.
 XML documents form a tree structure that starts at "the root" and branches to "the leaves".
 XML has very simple syntax rules. XML with correct syntax is "Well Formed". Valid XML also
validates against aDTD.
 XSLT is used to transform XML into other formats like HTML.
 All modern browsers have a built-in XML parser that can read and manipulate XML.
 The DOM (Document Object Model) defines a standard way for accessing XML.
 The XMLHttpRequest object provides a way to communicate with a server after a web page
has loaded.
 XML Namespaces provide a method to avoid element name conflicts.
 Text inside a CDATA section is ignored by the parser.
 Our XML examples also represent a summary of this XML tutorial.

 What to Study Next?
 Our recommendation is to learn about the XML DOM and XSLT.
 If you want to learn more about validating XML, we recommend DTD and XML Schema.
 Below is a short description of each subject.

 XML DOM (Document Object Model)
 The XML DOM defines a standard way for accessing and manipulating XML documents.
 The XML DOM is platform and language independent and can be used by any programming
language like Java, JavaScript, and VBScript.
 If you want to learn more about the DOM, please visit our XML DOM tutorial.

 XSLT (XML Stylesheet Language Transformations)
 XSLT is the style sheet language for XML files.
 With XSLT you can transform XML documents into other formats, like XHTML.
 If you want to learn more about XSLT, please visit our XSLT tutorial.

 XML DTD (Document Type Definition)
 The purpose of a DTD is to define what elements, attributes and entities are legal in an XML
document.
 With DTD, each of your XML files can carry a description of its own format with it.
 DTD can be used to verify that the data you receive, and your own data, is valid.
 If you want to learn more about DTD, please visit our DTD tutorial.

 XML Schema
 XML Schema is an XML based alternative to DTD.
 Unlike DTD, XML Schemas has support for datatypes, and XML Schema use XML Syntax.

Xml 150323102007-conversion-gate01

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