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Re: The meaning of conditional output and effect

From: Drew McDermott <drew.mcdermott@yale.edu>
Date: Thu, 2 Oct 2003 13:42:20 -0400 (EDT)
Message-Id: <200310021742.h92HgKu19136@pantheon-po04.its.yale.edu>
To: www-ws@w3.org

   [Yuzhong Qu]
   Based on my understanding, it seems that:

   1) A process can have any number of outputs, the information that
      the process provides, conditionally, after its execution.

   2) A process can have any number of effects, and effects are the
      result of the successful execution of a service.

   3) Outputs and effects can have conditions associated with them.

   My question is as follows!

   a) What's the intended meaning of the condition associated with a
   conditional output?

      Choice 1. if you get an output, then the condition associated
      with the output must be true (implied).

      Choice 2. if the condition associated with an output is
      evaluated to be true, then the output is **guaranteed** to be
      provided by the service.

      Choice 3. Neither 1, nor 2. (The condition is just a hint)

Choice 1 AND Choice 2.  You get the output with this name if and only
if the condition is true.

Perhaps someone else from the DAML-S group may want to correct me
here.  Some of our papers seem to blend together the _existence_ of an
output and the _value_ of an output.  E.g., instead of saying a
boolean output always exists, and has a value that depends on a
condition, we sometimes say that the output _exists_ only if the
condition is true.  This seems like a bad convention to me, if for no
other reason than that it works only for boolean outputs.

   b) In the case of mutilple conditional outputs, suppose two
   conditions associated with two different conditional outputs are
   satisfied in a situation, there should exist two parts in the
   output? (or two outputs?)

   Furthermore, two different (co)conditions being simultaneously
   satisfied are allowed? or this kind of usage is discouraged in the
   design stage?

Again, it seems to me that there is no problem with overlapping
conditions; but if two outputs are being used to express a single
boolean output (in that exactly one of the two outputs exists on any
given invocation of the service), then it would make no sense to have
overlapping coConditions.

   c) What's the intended meaning of the condition within a conditional effect?

The effect occurs ("is imposed") if the condition is true.

   d) How about in the case of multiple conditional effect?

Here it seems there is no room for ambiguity: If more than one
condition is true, then more than one effect is imposed.

                                             -- Drew McDermott
                                                Yale University CS Dept.
Received on Thursday, 2 October 2003 13:42:21 UTC

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