- From: Sheshagiri, Mithun <Mithun.Sheshagiri@hp.com>
- Date: Fri, 12 Sep 2003 19:43:09 +0100
- To: "'Monika Solanki'" <monika@dmu.ac.uk>, "Sheshagiri, Mithun" <Mithun.Sheshagiri@hp.com>
- Cc: "'Sheila McIlraith'" <sam@ksl.Stanford.EDU>, www-ws@w3.org
- Message-ID: <5E13A1874524D411A876006008CD059F07383747@0-mail-1.hpl.hp.com>
-----Original Message-----
From: Monika Solanki [mailto:monika@dmu.ac.uk]
Sent: Friday, September 12, 2003 6:18 PM
To: Sheshagiri, Mithun
Cc: 'Sheila McIlraith'; www-ws@w3.org
Subject: Re: Preconditions /effects vs Preconditions/Postconditions
Sheshagiri, Mithun wrote:
I might be be wrong but I think Monika and Sheila are talking about two
different conditions.
Monika is talking about Effect of execution being a condition and this she
terms as postcondition.
:-) .. Incidentally, by "Postcondition" , I mean precisely, the conditions
under which the "effect" is produced and which is alos a subclass of
ceCondition (which is also what Sheila is referring to), and not "the effect
of execution being a condition".
[Sheshagiri, Mithun]
I was under the impression that postcondition would be something that holds
after the service is executed.
AtomicProces: BuyBook
input: bookName
precondition: validUser
effect: points to disjointUnionOf(BookShippedEffect,
BookWillBeShippedEffect)
(BookShippedEffect, BookWillBeShippedEffect ) subClassOf ConditionalEffect
BookShippedEffect
+------ceEffect BookShipped
+------ceCondition BookImmAvail
BookWillBeShippedEffect
+-------ceEffect BookWillBeShipped
+-------ceCondition ¬BookImmAvail
BookImmAvail determines the effect so is it correct to call it a
postcondition?
On the other hand,
The effect of executing an AtomicProcess might be the assertion of a
condition. I thought this would be a postcondition
AtomicProcess: ValidateCC
input: CCname, CCnum, CCexpiry
effect: points disjointUnionOf(ValidEffect, InValidEffect)
(ValidEffect, InValidEffect) subClassOf ConditionalEffect
ValidEffect
+------ceEffect Valid
+------ceCondition CreditApproved
InValidEffect
+-------ceEffect InValid
+-------ceCondition ¬CreditApproved
ValidP sameValues Valid
Now Valid and ValidP could be subClassOf process.owl#Condition and Valid is
this case, IMHO, is a postcondition. And since ceEffect can point to
owl:Thing, this is permitted.
phew! I need a program that generates names for my classes and properties.
--Monika
(ceEffect points to a concept which is a subclassof
process:#Condition. And Sheila is talking about the condition being pointed
by ceCondition which decides the effect.
mithun
-----Original Message-----
From: Sheila McIlraith [mailto:sam@ksl.Stanford.EDU
<mailto:sam@ksl.Stanford.EDU> ]
Sent: Thursday, September 11, 2003 5:45 PM
To: Monika Solanki
Cc: www-ws@w3.org <mailto:www-ws@w3.org>
Subject: Re: Preconditions /effects vs Preconditions/Postconditions
Monika,
In DAML-S we are able to express conditional effects. These
are the side effects of a web service, as contrasted with its
output. E.g., AcmeBookSeller Web Service:
*output* is purchase receipt
*conditionalEffect* is comprised of a *condition* and an *effect*
the *effect* is that the book is sent to the customer,
under the *condition* that the book is in stock.
Side effects of services are critical to encode for the
purposes of automated WS composition, where such effects must
be considered in composing and executing services.
(Something we humans do all the time.)
As to how this relates to the wschor document you were
reading, it would be helpful to have the citation, but
without seeing it, here is a general answer. In the AI
planning literature the term "effect" is often used
synonymously with the term "postcondition". It is used
generically to captures the notion of effects which are
either conditional (i.e., conditional effects) or unconditional.
I'm guessing that ws-chor's notion of "postcondition" is used
in this context. It is possible that they have done away
with the notion of condition in their "postcondition",
because this is simpler, but I would argue, is not
sufficiently expressive to capture the true side effects of
web services.
As for what we need for WS composition, we need both the
*effect* and the *condition*, but the *effect* is the key notion.
Regards,
Sheila McIlraith
On Thu, 11 Sep 2003, Monika Solanki wrote:
In DAML-S we have Preconditions and Effects(Conditions and Effect).
BPEL4WS does not have the notion of Preconditions and
Postconditions(
to the best of my knowledge). However the ws-chor group
have defined
Precondition and Postcondition for the use cases in their
requirement
document.
I am wondering if the semantics of the "Conditions" for
"Effects" as
defined in DAML-S are different from "Post conditions" in
ws-chor doc,
as what we are really interested in is the condition itself. What
would be lost (just for the sake of argument) if we were to discard
the notion of "effect" and retain only the condition part
of "Effect"
i.e if I may call it, "Post condition". I say this because I feel
that in some way the effect part gets reflected in the
output. Maybe
"Effect" makes it more explicit. I guess even for service
composition,
what we are really interested in apart from input -output is the
conditions that are captured in Preconditions and Effects. I guess
what I am really trying to say is can we simplfy the notion of
Conditional effects by attributing it as "post condition" without
compromising anything that is not covered in any other property
parameter.
Any comments / thoughts well appreciated
Thanks,
Monika
--
**>><<**>><<**>><<**>><<**>><<**>><<**>><<**
Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Hawthorn building, H00.18
The Gateway
Leicester LE1 9BH, UK
phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk <mailto:monika@dmu.ac.uk>
web: http://www.cse.dmu.ac.uk/~monika <http://www.cse.dmu.ac.uk/~monika>
**>><<**>><<**>><<**>><<**>><<**>><<**>><<**
==============================================================
================
*** Moving to Dept. Computer Science, University of Toronto ***
Sheila McIlraith, PhD Phone: 650-723-7932
Senior Research Scientist Fax: 650-725-5850
Knowledge Systems Lab
Department of Computer Science
Gates Sciences Building, 2A-248
http://www.ksl.stanford.edu/people/sam
<http://www.ksl.stanford.edu/people/sam>
Stanford University
E-mail: sam-at-ksl-dot-stanford-dot-edu
Stanford, CA 94305-9020
--
**>><<**>><<**>><<**>><<**>><<**>><<**>><<**
Monika Solanki
Software Technology Research Laboratory(STRL)
De Montfort University
Hawthorn building, H00.18
The Gateway
Leicester LE1 9BH, UK
phone: +44 (0)116 250 6170 intern: 6170
email: monika@dmu.ac.uk <mailto:monika@dmu.ac.uk>
web: http://www.cse.dmu.ac.uk/~monika <http://www.cse.dmu.ac.uk/~monika>
**>><<**>><<**>><<**>><<**>><<**>><<**>><<**
Received on Friday, 12 September 2003 14:44:51 UTC