Re: Effects in OWL-S

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 15:48:24 UTC