Re: ?? Functional Dependency Question ??
Date: Tue, 21 Oct 2008 16:48:25 GMT
Message-ID: <tJnLk.2945$fF3.2848_at_edtnps83>
Bob Badour wrote:
> paul c wrote:
>> David BL wrote:
>> ...
>>
>>> Consider that in the FD world symbol X represents a set of attributes
>>> from some relation R. Let some tuple of R be given. Then as a
>>> proposition we interpret X as implying that we are given or can deduce
>>> (for the given tuple) the values of all the attributes associated with
>>> X. This interpretation makes it obvious that unions of attributes
>>> map to logical conjunctions, and that an FD maps to a logical
>>> implication.
>>
>> Thanks, but how does that interpretation work when R has no attributes?
>
> The same way DEE works with join.
I'm not sure about that. Maybe I'm being too literal in asking about this, but David B is talking about a mapping that involves values of attributes. I don't know what the value of "no attribute" is. Received on Tue Oct 21 2008 - 18:48:25 CEST