Re: Effects in OWL-S

I think this is better viewed as an effect, because it describes the
relationship between the before-state of a service (one where the input
msg was sent) and the after-state (where the input msg was consumed and an
output msg sent back).

I think theoretically we can always view states as persistent by assuming
that messages are treated as objects that are inserted into or deleted from
some kind of a database. Even for your example where the service is just an
arithmetic function you can view it as a service that has a state.

Even if you don't want to view such a service as having a state, the
description that you are proposing defines what the service does and is in
some sense similar to the frame axioms. But this analogy it also comes out
as a description of the effect.


	--michael  


> Michael Kifer wrote:
> > Steve,
> > According to you, a postcondition is nothing but a logical consequence of
> > the frame axioms. This is not very useful.
> > 
> > Why would you want to specify a postcondition like that if it can be
> > derived by a reasoning system? Because of the limitations of the reasoning
> > system? 
> > 
> > In my view, a postcondition should be viewed as a constraint on the
> > after-state of an action, if the effect of the action is non-deterministic.
> 
> What about my original example(s) - where what I want to express is 
> something about the relationship between the input(s) and output(s). 
> For instance, I want to say something like:
> 
>    (1)
>    interest_based_on_daily_compounding(InRate, InBalance, OutInterest)
> 
> where the predicate interest_based_on_daily_compounding is defined in 
> some standard accounting ontology.
> 
> Would you be comfortable calling (1) a postcondition?  Or does 
> postcondition, for you, have to do with an "after-state" that is persistent?
> 
> Thanks,
> David
> 
> > 
> > 
> > 	--michael  
> > 
> > 
> > Battle, Steve writes:
> > 
> >>Here's another way of thinking about this - essentially from the situation
> >>calculus. An effect describes things that are true _because_ of an action,
> >>whereas, a postcondition describes things that are true _following_ an
> >>action.
> >>
> >>Not everything that is true following an action is true because of it. A
> >>small example : If I add item A to my shopping trolley, then the effect is
> >>that "item A is in my trolley". If I then add item B to my trolley, then the
> >>effect is that "item B is in my trolley". Now, it's reasonable to assume
> >>that "item A is in my trolley" remains true because nothing I've done claims
> >>to effect the truth of it. So given that "item A is in my trolley" is a
> >>precondition of the "add item to trolley" action then "item A is in my
> >>trolley" is a reasonable post-condition, but not an effect. A lot of good
> >>work has gone into working out what post-conditions are reasonable given the
> >>effects (see the 'frame problem').
> >>
> >>Steve
> >>
> >>
> >>>-----Original Message-----
> >>>From: public-sws-ig-request@w3.org
> >>>[mailto:public-sws-ig-request@w3.org]On Behalf Of Charlie Abela
> >>>Sent: Wednesday, April 14, 2004 6:26 PM
> >>>To: Public-Sws-Ig@W3. Org
> >>>Subject: Re: Effects in OWL-S
> >>>
> >>>
> >>>
> >>>With all these ideas going on about preconditions and effects 
> >>>in OWL-S it is
> >>>quite difficult to capture the general idea of how to define 
> >>>actual effects
> >>>in WSs.
> >>>
> >>>I had the impression that an effect was something that will 
> >>>become true when
> >>>the WS has executed but that also brought some changes to the 
> >>>world, but now
> >>>there is talk of making use of post-condition instead. 
> >>>Actually from the
> >>>readings that I found, these two words seem to be used 
> >>>interchangeably,
> >>>depending on the research context, and thus I always presumed 
> >>>that they are
> >>>somewhat synonymous.
> >>>
> >>>What are the views of the OWL-S ppl on this? Cause with all 
> >>>these somewhat
> >>>radical changes being proposed it is quite difficult to get people to
> >>>actually make use of these ontologies. Will there every be a 
> >>>stable set of
> >>>OWL-S ontologies?
> >>>
> >>>Some time back there was a long discussion on the topic; I guess some
> >>>clarification is now due.
> >>>
> >>>Regards
> >>>
> >>>Charlie
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>
> >>
> > 
> > 
> 
>

Received on Tuesday, 27 April 2004 18:19:27 UTC