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Re: Preconditions /effects vs Preconditions/Postconditions

From: Charlie Abela <charlie@semantech.org>
Date: Tue, 16 Sep 2003 04:14:25 +0800
Message-ID: <1063656865.3f661da1d93fc@>
To: Jeff Lansing <jeff@polexis.com>
Cc: "www-ws@w3.org" <www-ws@w3.org>

I wonder whether it is expected for a Web Service developer creating such a 
service to go into such a hussle as to identify all these possible combinations 
of pre and postconditions, effects, you name it. 

I think the more this is complicated the less it is looked at in a favourable 
way. I also think that there should be some way by which to say that given a 
number of preconditions and postconditions or effects then a service can be 
identified, and other extended information regarding such service would be made 
available in some other location, maybe also in some repository that defines 
general business logic.


Quoting Jeff Lansing <jeff@polexis.com>:

> Walden Mathews wrote:
> >How about this:
> >
> >The post-condition of a (successful) credit card transaction
> >is that your loan balance is increased and your available credit
> >is decreased, both by the transaction amount.
> >
> >  
> >
> If post-conditions are conditions, then there are 2 post-conditions 
> here, which could be stated as:
> 1) the increase in the loan balance is equal to the transaction amount
> 2) the decrease in the available credit is equal to the transaction amount.
> (and which could be conjoined into a single post-condition, if you prefer).
> There are also two effects:
> a) the loan balance has been increased (by the transaction amount, as it 
> happens)
> b) the available credit has been decreased (also by the transaction 
> amount, as it happens).
> Jeff

Charlie Abela
Research Student,
CSAI, Department,
University of Malta

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