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Re: No exceptions?

From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 30 Jun 2006 22:31:23 GMT
Message-ID: <%Chpg.111333$Mn5.20411_at_pd7tw3no> 






paul c wrote:

> Jon Heggland wrote:




>> paul c wrote:

>>> Let me re-phrase my original question:  Is there a logical flaw in


>>> substituting TABLE_DUM for x in the expression "x join y" when x is not

>>> in the catalogue?

>>>

>>

>> I don't know what precisely you mean by "logical flaw", so I'll pass

>> judgement. If something should be substituted for x (a "default value",

>> so to speak), TABLE_DUM does seem the natural choice, though, as it

>> corresponds to false/zero in some sense.

>> ...




[Quoted] I suppose my "logic", if I may call it that, went like this (at 
evaluation time):



    
  
  1.   according to syntax, x must be a relation
[Quoted]   
  2.   according to the catalogue, there are no attributes for a relation 
named x, so given that the syntax insists x is a relation, it must be 
the same relation as either TABLE_DEE or TABLE_DUM
  
  3.   because x is not in the catalogue, it has no tuple in the database
[Quoted]   
  4.   since x has no attributes and no tuple, it must have the same value 
as TABLE_DUM







[Quoted] That seems okey-dokey, but what if I make an innocuous change to step 3, 
eg.,



[Quoted] 3) because x is not in the catalogue, it has no known value in the database



Now, it seems I'm stuck, the choice between DEE and DUM is 
indeterminate.  So I guess by logical flaw, I meant either a mistake in 
the reasoning OR a misleading assumption.



p
Received on Sat Jul 01 2006 - 00:31:23 CEST












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