- From: Jos de Bruijn <jos.de-bruijn@uibk.ac.at>
- Date: Mon, 15 Sep 2003 09:38:03 +0200
- To: Monika Solanki <monika@dmu.ac.uk>
- Cc: www-ws@w3.org
- Message-ID: <3F656C5B.4000500@uibk.ac.at>
Dear all, Here is a better quote from the WSMF document about what a post-condition is in terms of Web Services: Post-conditions describe what a web service returns in response to its input. A post-condition provides a declarative description of the relation that must hold between the input and the output of the service. A limitation of DAML-S in my opinion is the limited of the effect. Since DL does not include variables, it is currently not possible to formulate the post-condition of the service in the DAML-S "effect". Best, Jos 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, therefore this condition is the "Post condition". 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 > **>><<**>><<**>><<**>><<**>><<**>><<**>><<** > -- Jos de Bruijn Institute of Computer Science University of Innsbruck Technikerstraße 13 A-6020 Innsbruck Austria Tel: +43 512 507 6475 Fax: +43 512 507 9872 Email: jos.de-bruijn@uibk.ac.at Homepage: http://homepage.uibk.ac.at/~c703239/ Next Web Generation research group http://www.nextwebgeneration.org/
Received on Monday, 15 September 2003 03:38:14 UTC