HTML -> XML

Running in an 8i environment with 9iAS. Application generates HTML using the PL/SQL web toolkit. Not come into contact with XML etc - but understand that if the app were modified to generate XML then one could apply a stylesheet to define how the data is rendered in a browser.

I am looking for a 'primer' resource - something that explains in simple terms how this works, what minimum technology stack etc would be required.

Any pointers greatly appreciated.

Thanks!

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jeremy