1. Define the types of updates you wish to do to these XML and HTML objects
2. Learn about (and, if they don't exist, write) methods that do this for you already
3. Describe (in some design methodology you like, which could be ad-hoc or on-the-fly) how you wish to use said methods
4. Use said methods

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.