Re: A Logical Model for Lists as Relations

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Thu, 11 May 2006 23:47:28 +0200
Message-ID: <4463b0d2$0$31656$e4fe514c@news.xs4all.nl>

Gene Wirchenko wrote:

> mAsterdam 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. 

My teenage daugther would now loudly and slowly say "duh-uh". A collegue of mine would make two jokes about technically correct but useless statements.

But they are not me.

I say: No, the 2nd and 3rd assertions are the same. (Try to just look at them without any implementation strategy   in mind)

Their context is what is different.
Furthermore, /if/ these assertions are relevant to us, we need their context.

> 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.  

You had to do some quite sophisticated human interpretation of both the assertions, their context, and the relationship between assertion and context to arrive at that.

> If that John is
> making a statement is what is to be recorded, then it is a different
> situation.

Ceterum censeo Carthaginem delendam esse. Context matters. Received on Thu May 11 2006 - 16:47:28 CDT