Re: Storing data and code in a Db with LISP-like interface

From: paul c <toledobythesea_at_oohay.ac>
Date: Mon, 17 Apr 2006 02:40:26 GMT
Message-ID: <ueD0g.30741$P01.28425_at_pd7tw3no>


JOG wrote:

> Bob Badour wrote:
> 

>>JOG wrote:
>>
>>
>>>topmind wrote:
>>>
>>>
>>>>Nulls are a vendor-specific idea, not inherent to relational.
>>>
>>>While I agree with much of your post, nulls now appear to me to be
>>>essential to the relational model (whatever their rights and wrongs).
>>>If one fully normalizes a database then it is likely a join will
>>>require the use of null to pad the resulting virtual relation. Just
>>>because these relations are not persisted on disk, makes them no less
>>>'relations' in the sense of Codd's algebra. As such i am currently
>>>struggling with how one can be against nulls (as per Date's perfectly
>>>justified view) but pro-RM from a completely theoretical standpoint.
>>
>>With all due respect, is it possible you confound NULL with missing
>>information?
> 
> 
> Quite possibly Bob, and if so I stand corrected. I was referring to
> fill values generated via outer joins, which are of course not
> synonomous with the black holes that are SQL NULLS. I presonally avoid
> external joins as much as possible, but they seem prevalent enough that
> (if I recall correctly) they figure in Date and Darwen's D.
> 
> 

>>Obviously, missing information is a difficult problem no matter what
>>data model one uses. We currently have no theory regarding missing
>>information which means we have no theory to overcome the practical
>>problem in any data model.
>>
>>In fact, missing information is rather anathema to science. Take
>>interpolation for example: We either use sampling theory and error
>>analysis to decide whether it is valid to interpolate, or we interpolate
>>predictively as a method to falsify an hypothesis. Neither use accepts
>>truly missing information as fact. Ditto for extrapolation.
>>
> 
> 
> Tell me about it. I'm of the view that if my data is missing and I
> can't satisfy the required predicate, I shouldn't be entering it into
> the damn extension at all. ...

Right.

p Received on Mon Apr 17 2006 - 04:40:26 CEST

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