Block Definition Diagram query

[Vikas]

Hi,
In my Block Definition Diagram, the input parameters and the return
type of a Operation must be XML. The input parameters and the return
type may have different XML structure (i.e they use different XML
schema).

What is the best way to model this ? If I use primitive type "String"
for input and return type this doesn't capture the structure of the
XML. Should I use DataType block to describe the structure for each
type ?

Thanks in advance,
Vikas Patel