- From: Monika Solanki <monika@dmu.ac.uk>
- Date: Mon, 15 Sep 2003 09:01:32 +0100
- To: www-ws@w3.org
Hi David, David Martin wrote: > Hi Monika - > > I believe you have been saying that a "postcondition" in DAML-S (if > that term were used) would be the same as the condition of a > conditional effect. I guess, since we don't normally talk about > "postconditions" in DAMl-S documentation, there's no precise answer. > But I tend to think of it differently than (I think) you've been > saying. more below ... > > Monika Solanki wrote: > > >> Short reply for now. >> >> I guess, we all are talking about the same thing. The difference is >> maybe only in the way we put it across. Post condition is indeed the >> condition which is true after service execution. However, in the >> terminology that we use in DAML-S, an "Effect" may be produced >> under certian condition and this condition is true only after service >> execution, > > > > If you are talking about conditions of conditional effects, it > doesn't seem quite accurate to say they are true only after service > execution. At least for some such conditions they may also be true > before service execution. For example, "book in stock" might > certainly be true (or false) both before service execution and after. > > therefore this condition is the "Post condition". > > Actually, I tend to think of "postcondition" and "effect" as > synonymous. So then, in my mind at least, a postcondition would not > be the same as the condition part of a conditional effect; rather it > would be the same as the effect part. The ambiguity in thinking about it in this way is that the "Effect" part maps to "Thing", while only the "Condition" part maps to "Condition". This is also what I had mentioned in the first or second email of this thread. Is this "Effect part" a logical formulae, if it is the same as a condition? If it were indeed to be , then I believe, that ceEffect should map to "Condition" as well , although I am still not sure, if the semantics of "Post Condition" would be that of "Effect " or "Condition part of Effect" or a conjunction of the two. > > I can't say for sure whether others in the DAML-S Coalition hold the > same view on this as me, but I think most probably do. > > Regards, > -- David > > Quoting > >> from WSMF document: >> >> The pre-condition is the condition that has to be true >> for the input in order for the web service to be able to successfully >> execute it. The postcondition >> is the condition that holds once the complex service has been executed >> successfully, i.e., it defines constraints on its output. >> >> >> Sheshagiri, Mithun wrote: >> >>> >>> >>> -----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] 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 >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>>> >>>> >>> >>> -- **>><<**>><<**>><<**>><<**>><<**>><<**>><<** >>> 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 >>> **>><<**>><<**>><<**>><<**>><<**>><<**>><<** >>> >> >> -- >> **>><<**>><<**>><<**>><<**>><<**>><<**>><<** >> 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 >> **>><<**>><<**>><<**>><<**>><<**>><<**>><<** >> > -- **>><<**>><<**>><<**>><<**>><<**>><<**>><<** 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 **>><<**>><<**>><<**>><<**>><<**>><<**>><<**
Received on Monday, 15 September 2003 03:55:05 UTC