XML Syntax Rules

The syntax  rules  for  XML are very simple and strict. These  are  easy to learn and  use. Because of this, creating software that can read and manipulate XML is very easy. Xml enables an user to create  his own tags.

Note - XML documents use a self-describing and simple syntax

Let's develop a simple XML document :

The XML declaration:  Always the first line in the xml document: 

The XML declaration should always be included. It defines the XML version and the character encoding used in the document. In this case the document conforms to the 1.0 specification of  XML and uses the ISO-8859-1 (Latin-1/West European) character set.

Root Element: The next line defines the first element of the document . It is called as the root element 

Child Elements: The next 4 lines describe the four child elements of the root (To, From, Subject and Body).

And finally the last line defines the end of the root element .

you may feel from this example that the XML document contains a  E-mail To Rohan  From Amit. Don't you agree that XML is quite self-descriptive?

Now let's discuss its syntax-rules which are very simple to learn.

All XML elements must have a closing tag

In XML all the elements must have a closing tag like this:

XML tags are case sensitive

XML tags are case sensitive. The tag <To> is different from the tag <to>.Hence the opening and closing tags must  be written with the same case:

XML Elements Must be Properly Nested

Improper nesting of tags makes no sense to XML. In XML all elements must be properly nested within each other like this in a logical order:

XML Documents Must Have a Root Element

All XML documents must contain a single tag pair to define a root element. All other elements must be written within this root element. All elements can have sub elements called as child elements. Sub elements must be correctly nested within their parent element:

Always Quote the XML Attribute Values 

In XML the attribute value must always be quoted. XML elements can have attributes in name/value pairs just like in HTML. Just look the two XML documents below.  

<?xml version=1.0 encoding="ISO-8859-1"?>
<E-mail date=12/11/2002/>

The second document is correct:

<?xml version="1.0" encoding="ISO-8859-1"?>
<E-mail date="12/11/2002"/>

With XML, White Space is Preserved

With XML, the white space in a document is  preserved .

So a sentence like this :   Hello              How are you, will be displayed like this:

Comments in XML

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