help with extending saxparser todefine some addtional rules

[Sharad Singh]

Hi,

I am using the SAXParser provided in the xerces.jar through which i am able to validate xml based on dtd validations. Now I need to extend the Saxparser functionality so that i can define some additional rules and perform validations on that rules. Can anyone please tell me how can i do that?

for EXAMPLE i would like to validate _expression_ : a+(b+c)
on following grammar that the brackets are properly closed and the operator + must have two operands....
I will have the _expression_ written in the xml as
<mytag> a+(b+c) </mytag>

thanks in advance...
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Thanks/Regards
Sharad Kumar Singh