W3C home > Mailing lists > Public > www-ws@w3.org > September 2003

RE: Preconditions /effects vs Preconditions/Postconditions

From: Sheshagiri, Mithun <Mithun.Sheshagiri@hp.com>
Date: Fri, 12 Sep 2003 17:53:57 +0100
Message-ID: <5E13A1874524D411A876006008CD059F07383746@0-mail-1.hpl.hp.com>
To: "'Sheila McIlraith'" <sam@ksl.Stanford.EDU>, Monika Solanki <monika@dmu.ac.uk>
Cc: www-ws@w3.org

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. (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] 
> Sent: Thursday, September 11, 2003 5:45 PM
> To: Monika Solanki
> Cc: 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
> > web: 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
> Stanford University    
>                E-mail: sam-at-ksl-dot-stanford-dot-edu
> Stanford, CA 94305-9020
> 
> 
> 
> 
> 
Received on Friday, 12 September 2003 13:04:25 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Tuesday, 3 July 2007 12:25:44 GMT