DAML-S: Conditional E/Os

Hi All,
              Lets take the example of ExpressCongoBuy atomic service. 
This service has 2 conditional  outputs- congoOrderShippedOut and 
congoOutOfStockOutput. Only one of these will materialize (depending on 
the BookInStock and BookOutStock conditions) on service execution.

In this case what is the use of BookInStock/BookOutStock? The "values" 
of these variables are not part of the advertisement, since the value 
depends on congoBuyBookISBN (input). The value of this variable can be 
known only when the response from service provider is received. Now, if 
I get the desired output then I won't be interested in BookInStock 
because I know it is true. If I get the undesired output, then I can use 
the value of the condition variable to determine whether failure was due 
to a normal problem (book being out of stock) or a abnormal problem 
(book was in stock and still the service did  not execute as intended). 
So, is diagnosis the only purpose of condition variable.

--
Mithun Sheshagiri
http://www.cs.umbc.edu/~mits1