>>Variable definition
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Section 2.4.2 is not clear about what kind of data a "variable" as defined 
here can contain. Should it be limited to info that are relevant to 
interaction? For example, in a credit approval choreography, while it's 
necessary to communicate the "approve"/"reject" decision,  I don't see any 
reason a choreography should expose data used to make such decision.  

In addtion, variable definition is another example that different grouping 
criteria are used. I am very lost in trying to understand  the differences of 
each kind of variables here

I also note that the definitions are the same for "information exchange 
variable" and "information variable".