The XML syntax has the following rules:
1. - Any label must have a closing tag (</tag>)
2. - The tag names are case sensitive.
<message> and <Message> are different labels, because the second begins with a capital.
3. - The tags must be nested correctly.
We can not close a parent tag if we have not closed before all the labels of their children.
4. - Each XML document must have a single parent or root element.
For example, for the following XML, document root is <messages>, which of course must be closed at the end.
5. - All attributes must be enclosed in double quotes.
All tags may or may not have attributes.
An attribute is used to provide additional information to the contents of a label.
For example, the tag may have an attribute <message> 'type' indicates the message type.
6. - Do not use special characters.
You can not use the characters (< , >, &, ', ") at any value of the labels.
7. - Comments
Comments can be put anywhere in an XML document