How do i know what are the elements ,subments ,attributes in a xml file ?

For a struts2 application i have used validations using the validation.xml

In that i use various elements , How do i know ,what are the elements ,subelemts are there ,and what are the attributes for them ,what are the values i shoukd use for the attributes ....?

I have saw in the dtd url mentioned in DOCTYPE but there is no detail information about the elements ...

Thank

I think you should go for XML then you can uderstand what is DTD and how to create XML file from that .
After that you can get what are element ,attribute.

I mean to say that while creating the validation file ,I am not knowing what will the value for the attributes in the elements
for ex.

<field-validator type="requiredstring"> what all the values type attribute of <feild-validator > element with have ,how are they used ....

like that where can i find detail information of an element ,its subelemts ,its attributes ,the attribute values .........

Sorry I take it wrog
It means you need details information about that attributes and elements
Its better to go with struts documentation or any good book

The Struts 2 documentation?

http://struts.apache.org/2.1.8/docs/validation.html