UDF questions

[Mark]

What methods should I be implemented when creating my own UDF's other 
than the ones that are required.

For example, when creating a EvalFunc<Tuple> I see there are a bunch of 
classes that override outputSchema, or getArgToFuncMapping.

Should I consider overriding these methods too? Is there any 
documentation on what these methods do and when and why someone should 
override them?

Thanks