FW: Last Call Issue: CHOICE WITH MIXTURE OF BLOCKING AND NON-BLOCKING ELEMENTS

 

-----Original Message-----
From: public-ws-chor-request@w3.org
[mailto:public-ws-chor-request@w3.org] On Behalf Of Gary Brown
Sent: 05 January 2005 14:22
To: public-ws-chor@w3.org
Subject: Last Call Issue: CHOICE WITH MIXTURE OF BLOCKING AND
NON-BLOCKING ELEMENTS


If a choice construct has a mixture of blocking and non-blocking
elements, then it is not clear how these should be processed.

"If the choice has Work Units with guard conditions, the first Work Unit
that matches the guard condition is selected and the other Work Units
are disabled."

Does this mean the 'first' with respect to time, or the first in lexical
order?

For example, if the choice construct has two elements, the first one
blocks awaiting some information, while the second element is
non-blocking:

- should the choice construct evaluate the first item and then suspend
until the first element has a known value.

- or should the blocking element be skipped as its value cannot be
determined, and therefore the second element is evaluated?

However, if this second element evaluates to false, then does this mean
that the choice suspends awaiting one of the blocked elements (i.e. the
first element in this case) to be evaluated to true, or until no
elements remain to be evaluated?

The semantics of the choice construct are unclear in this situation.

Regards

Gary and Steve