relationships. They have simple naming rules.

XML Elements are Extensible
XML documents can be extended to carry more information.

Look at the following XML example:

Let’s suppose that we create an application to fetch data from the above XML document and produce this output:

E-mail

To: Rohan
From: Amit

Be ready for a cruise...i will catch u tonight

Now, the author wants to add a new feature (let it be a subject line). He can easily achieve it by adding one more tag ie..<Subject>in the xml document. So the new modified xml document will look like this:

Now the new generated output will look like this:

E-mail

To: Rohan
From: Amit

Subject: Surprise....

Be ready for a cruise...i will catch u tonight

XML Elements have Relationships

Elements in a xml document are related as parents and children.

Imagine that this xml document is a description of e-mail:

Here, E-mail is the root element while To, From, Subject and Body are the child elements of the E-mail. Here, E-mail is the parent element of To, From, Subject and Body. To, From, Subject and Body are siblings (or sister elements)
because they have the same parentage. Hence
all the XML Elements have Relationships.

XML Element Naming conventions:

XML elements must follow these naming conventions:

Names must not start with a number or punctuation character but it can contain letters, numbers, and other characters without spaces.

Names must not start with the letters xml (or XML, or Xml, etc).

XML Attributes

XML elements can have attributes in the start tag, just like HTML. Attributes are used to provide additional information about elements. 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