Implementation issue from Gary:

. Business messages can be correlated to a channel instance and
choreography session using identity information derived (through
the use of token locators) from the message contents
.  However, channels passed over other channel instances do not
carry any business information, and therefore how can they be
correlated?
.  Approach taken in pi4soa is currently restricted to use of WSAddressing
endpoint reference, which it stores the identity token
values of the channel on which the exchange is occurring 
however this is not interoperable, as it relies on prior knowledge
of the identity token encoding within the endpoint reference

. Channel passing is also restrictive, as it can only be passed within
its own exchange
. This is currently necessary to enable the formal verification to
identify where the channels are being passed

. However, for subsequent versions of CDL, we should investigate
the ability to describe message exchanges where a channel's
details are passed as part of a business message, but still remain
explicit enough for formal verification.