CPP/CPA specification clarification

[Eric Chiu <echiu@imservice.com>]

I have read through the CPP/CPA specification several times, and trying to 
understand the implementation issues implied in the document. 

I assume the goal is to provide a clear guideline for inter-enterprise 
communication by providing a standard document set that can be 
exchanged, similar to the X12 document standard. 

How does this piggyback on X12, or not? Also what's the dependency 
on the registry? Do I pull the CPP and CPA from the repository? 

Does the CPP and CPA become the payload when transferred as a 
message? 

Perhaps an expert on this topic can provide a step-by-step guideline
on usage. 

Thanks,
Eric Chiu