RE: Preconditions /effects vs Preconditions/Postconditions

I agree that this post-condition reflect the terminology better. Also I
believe for applications that they don't distinguish the output, effect, and
postcondition in a well-agreed way.  

Thanks.
Yinsheng

> -----Original Message-----
> From: Charlie Abela [mailto:abcharl@keyworld.net]
> Sent: Monday, September 15, 2003 1:05 PM
> To: Li, Yinsheng
> Cc: www-ws@w3.org
> Subject: RE: Preconditions /effects vs Preconditions/Postconditions
> 
> 
> IMHO, the distinction between the post-condition and effect is not a
> clear-cut distinctionme definitions that I found for 
> "post-condition" over the web:
> 
> i. The post condition is a statement of what the world should 
> look like
> after an operation. For instance if we define the operation 
> square on a
> number the post-condition would be of the form result = this 
> * this (where
> result is the output and this is the object on which the operation was
> invoked). The post condition is a useful way of saying what 
> we do, without
> saying how we do it, separating interface from implementation.
> ii. Post Condition: State of the system after executing the operation.
> iii. A post-condition specifies some facts about the world 
> which can be
> expected to be valid after the service operation has finished 
> its execution
> regularly.
> 
> As for the defined example I'd say that the distinction could 
> become clearer
> if:
> 
> Post-condition: credit card billed/not billed
> Effect: transaction successful/failed
> 
> Charlie
> 
> -------------------------------------------------
> Charlie Abela
> Research Student,
> Dept. of Computer Science and AI
> University of Malta,
> MSD06. Malta
> Web: http://www.semantech.org
> Email: abcharl@keyworld.net
> 
> -----Original Message-----
> 
> 
> 
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Received on Monday, 15 September 2003 13:19:47 UTC