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Re: Semantics of Preconditions and Effects

From: Monika Solanki <monika@dmu.ac.uk>
Date: Wed, 27 Aug 2003 18:34:12 +0100
Message-ID: <3F4CEB94.4060708@dmu.ac.uk>
To: Sheila McIlraith <sam@ksl.Stanford.EDU>
Cc: daml-process@bbn.com, www-ws <www-ws@w3.org>

Hi Sheila,

Thanks for your Reply.

Sheila McIlraith wrote:

>Hi Monika,
>
>As you know, DAML-S enables the modeler to associate the following
>properties with a process
>- input
>- (conditional) output
>- precondition
>- (conditional) effect
>
>"inputs" and "outputs" should be obvious.  A "precondition" describes some
>state of the world that must be true in order for the service to be
>invoked.  "(condiitonal) effect" describes the side effect of the program.
>E.g., if executing the amazon.com service has the side effect that a
>book is shipped to the address provided, then this is encoded as a
>"(conditional) effect".  Note it is conditional if the effect occuring
>depends on some condition.
>
>As we argued in the paper you referenced below, "inputs" and "outputs"
>can be regarded as "knowledge preconditions" and "knowledge effects".
>That is, they pertain to the agent (executors) state of knowledge.
>If ISBN is the "input" to amazon, it is identical to say that the agent
>must *Know* the ISBN number;  this is a knowledge precondition of the
>process.  Likewise, if the "output" is the price of the book,
>then it follows that the knowledge effect of the process is that the
>agent *Knows* the price of the book.
>
>So, to answer your question, the agent can have knowledge effects, but
>they are encoded as and "output" of a process.  That is the way
>the agent's state of knowledge is updated.  Note also that the agent
>*Knows* all the effects of the process it is invoking, so it follows
>that any "effect" is also a "knowledge effect".
>
So does it actually mean that these knowledge preconditions and effects 
are ineffect  manifestations of "input" and "output" and different from 
the actual preconditions and effects that we usually need for a DAML-S 
specification? I mean, can we actually use these knowledge preconditions 
and effects to specify the preconditions and effects of the service?

>Sheila McIlraith
>

-- 
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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
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Received on Wednesday, 27 August 2003 13:28:58 GMT

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