Re: A Logical Model for Lists as Relations

On Thu, 11 May 2006 19:45:43 +0200, mAsterdam <mAsterdam_at_vrijdag.org> wrote:

>David Cressey wrote:
>> x wrote:
>>>David Cressey wrote:
>>>>Jay Dee wrote:
>>>>
>>>>>>If one has a numeric index that differs for each tuple,
>>>>>>one never has duplication.
>>>>>>If one has duplication, one wonders how to refer to the
>>>>>>duplicates. As Codd observed long ago, once one has said
>>>>>>a thing is true, what does saying it again achieve?
>>>>>
>>>>>Yes, I agree. If one were, for example, compiling a list of what
>>>>>folks were going to bring to the picnic, it might be nice to know
>>>>>that potato salad had been recorded many more times than fried
>>>>>chicken...
>>>
>>>>That's counting, not asserting. Asserting something twice is no more
>>>>consequential than asserting it once.
>>>
>>>The assertion depend on when, where, who, ... made it. :-)
>
>Yep. See below.
>
>> As data in databases is generally understood, the database itself is making
>> an assertion, once a transaction has been committed and accepted that makes
>> that assertion. Of course, an application could attach to every assertion
>> an indication of the author of the assertion. In which case, that same
>> author, asserting something more than once is no more consequential than
>> that author asserting it once.
>
>I said this before:
>Implementation strategies we are comfortable with tend
>to bias the way we state problems.
>
>At 10:10 John asserts "Two minutes ago Bob insulted me."
>
>At 11:30 John asserts "Two minutes ago Bob insulted me again."
>
>At 15:10 John asserts "Two minutes ago Bob insulted me again."
>
>Hardly consequential, though. Admitted.
>
>:-)

     The assertions are different because of the time element. John's assertions are that he was insulted at three different times. Contrast with:

     At 10:10 John asserts "Two minutes ago Bob insulted me."

     At 10:28 John asserts "Twenty minutes ago Bob insulted me."

     At 11:08 John asserts "One hour ago Bob insulted me."

     These all are that Bob insulted John at 10:08. If that John is making a statement is what is to be recorded, then it is a different situation.

Sincerely,

Gene Wirchenko Received on Thu May 11 2006 - 23:19:38 CEST