Re: No exceptions?

From: paul c <>
Date: Fri, 30 Jun 2006 01:18:41 GMT
Message-ID: <RZ_og.109403$Mn5.72708_at_pd7tw3no>

Bob Badour wrote:
> paul c wrote:

>> Bob Badour wrote:
>>> paul c wrote:
>>>> J M Davitt wrote:
>> ...
>>>>> It almost seems as though you want to declare an analogue for DUM,
>>>>> syntax-check some expressions, and add attributes to your relation
>>>>> with the confidence that your expressions are still correct.
>>>> Not exactly how I thought of it, but I think that's fair, after all, 
>>>> one can add attributes, subject to one's external conception, to 
>>>> relation definitions that don't have empty headings, in fact not 
>>>> that the observation is of any use, that seems to be what happens 
>>>> when one defines a relation with one attribute.
>>> I suggest an empty candidate key in a relation with any number of 
>>> attributes is closer.
>> I don't catch your drift.  If we are on the same page, then trying to 
>> equate a relation that has either no rows or one row with a relation 
>> whose name is mis-spelled is indeterminate.  If doing that is the same 
>> then I would have to give up on my original question.

> You suggested that adding an attribute to a degree zero relation is a
> degree one relation. However, whether one adds one attribute or an
> arbitrary number of attributes is less important than the fact that the
> candidate key will have an empty set of attributes.
> ...

Thanks, I will try to ponder that in some way different from how I've been looking at it. Strictly speaking, I wasn't aware that one could 'add' an attribute to a relation, nor that any 'key' would persevere.

> Identifying the error condition is easy. The problem of identification
> only arises after you replace the error with DEE or DUM.
> ...

It seems (as usual) that I haven't explained myself well enough. While at the UI, I think most people would consider a spelling error an error, I would like, at a very low internal level, to ignore typo's of that sort, evaluate it as written, and give a result that is logically consistent (assuming that is logically possible). I want to postpone what error decisions are shown at the UI level.

p Received on Fri Jun 30 2006 - 03:18:41 CEST

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