Re: Surrogate Keys: an Implementation Issue
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sun, 30 Jul 2006 19:44:09 GMT
Message-ID: <d_7zg.29448$pu3.405787_at_ursa-nb00s0.nbnet.nb.ca>
>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>> news:qt4zg.281144$IK3.267521_at_pd7tw1no...
>>
>>> Brian Selzer wrote:
>>>
>>>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>>>> news:zTOyg.269253$IK3.233927_at_pd7tw1no...
>>>>
>>>>> Brian Selzer wrote:
>>>>>
>>>>>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>>>>>> news:g9Nyg.263082$iF6.250988_at_pd7tw2no...
>>>>>>
>>>>>>> Brian Selzer wrote:
>>>>>>>
>>>>>>>> What's the point of a database if it doesn't reflect some aspect
>>>>>>>> of reality. ...
>>>>>>>
>>>>>>> To talk precisely about whatever we want to talk about. Nothing
>>>>>>> more. Doesn't need to be real.
>>>>>>>
>>>>>> Agreed. But even a conceived universe subsumes certain absolutes,
>>>>>> such as time.
>>>>>>
>>>>> In that case, the statements in the database should talk about
>>>>> time, ie., aspects of time. These are different from statements
>>>>> about the time it takes the database to say something.
>>>>>
>>>> There can be no discussion without time. Relational assignment
>>>> cannot exist without the concepts of before and after. ...
>>>
>>> For some people, unfortunately, that is a matter of belief. In the
>>> context of RT, I'd say it is mere willfullness. To see why, try to
>>> avoid the words 'before' and 'after', using say, x and y instead to
>>> stand for two relations (which might be the same). To ask which one
>>> (or two) does the db state at this moment in time is the same as
>>> asking does it state x or does it state y. But to ask which one(s)
>>> was stated yesterday requires that we deliberately add time
>>> information. This is a choice that allows us to ask the second
>>> question. The point is that we may not be interested in the second
>>> question and choose not to state information about time which makes
>>> the use of a time concept arbitrary.
>>
>> But the assignment operation by its nature determines the order of the
>> states x and y: one must always precede the other because the
>> operation itself produces that other.
>> ...
>>> require any notion of time. Nor does algebraic difference.
>>
>> Could you please elaborate on that? Replacement, as I understand it,
>> subsumes that something exists and will be superceded by something
>> else. Algebraic difference isn't even related to assignment.
>> Difference is an operator, assignment is an operation. I don't
>> understand why you included it. Perhaps you're conflating the
>> concepts of operator and operation.
Date: Sun, 30 Jul 2006 19:44:09 GMT
Message-ID: <d_7zg.29448$pu3.405787_at_ursa-nb00s0.nbnet.nb.ca>
paul c wrote:
> Brian Selzer wrote: >
>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>> news:qt4zg.281144$IK3.267521_at_pd7tw1no...
>>
>>> Brian Selzer wrote:
>>>
>>>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>>>> news:zTOyg.269253$IK3.233927_at_pd7tw1no...
>>>>
>>>>> Brian Selzer wrote:
>>>>>
>>>>>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>>>>>> news:g9Nyg.263082$iF6.250988_at_pd7tw2no...
>>>>>>
>>>>>>> Brian Selzer wrote:
>>>>>>>
>>>>>>>> What's the point of a database if it doesn't reflect some aspect
>>>>>>>> of reality. ...
>>>>>>>
>>>>>>> To talk precisely about whatever we want to talk about. Nothing
>>>>>>> more. Doesn't need to be real.
>>>>>>>
>>>>>> Agreed. But even a conceived universe subsumes certain absolutes,
>>>>>> such as time.
>>>>>>
>>>>> In that case, the statements in the database should talk about
>>>>> time, ie., aspects of time. These are different from statements
>>>>> about the time it takes the database to say something.
>>>>>
>>>> There can be no discussion without time. Relational assignment
>>>> cannot exist without the concepts of before and after. ...
>>>
>>> For some people, unfortunately, that is a matter of belief. In the
>>> context of RT, I'd say it is mere willfullness. To see why, try to
>>> avoid the words 'before' and 'after', using say, x and y instead to
>>> stand for two relations (which might be the same). To ask which one
>>> (or two) does the db state at this moment in time is the same as
>>> asking does it state x or does it state y. But to ask which one(s)
>>> was stated yesterday requires that we deliberately add time
>>> information. This is a choice that allows us to ask the second
>>> question. The point is that we may not be interested in the second
>>> question and choose not to state information about time which makes
>>> the use of a time concept arbitrary.
>>
>> But the assignment operation by its nature determines the order of the
>> states x and y: one must always precede the other because the
>> operation itself produces that other.
>> ...
> > I think you are pre-supposing a particular imperative implementation. >>>> replacement, aka pointer replacement. Logical replacement doesn't
>>> Maybe the confusion arises from Codd mentioning 'time-varying
>>> relations'. In the interest of making his main points in an efficient
>>> way, I suspect he didn't want to dot every last 'i'. As soon as you
>>> talk about relational assignment you are talking about variable
>>> require any notion of time. Nor does algebraic difference.
>>
>> Could you please elaborate on that? Replacement, as I understand it,
>> subsumes that something exists and will be superceded by something
>> else. Algebraic difference isn't even related to assignment.
>> Difference is an operator, assignment is an operation. I don't
>> understand why you included it. Perhaps you're conflating the
>> concepts of operator and operation.
> > Sorry, I don't see what words like subsuming or conflating have to do > with this unless they are what you are trying to embody for mystical > reasons.
Difference and assignment are equally operations, and the symbols that signify the operations are operators. Apparently, words mean something unique in Selzer's mind. That could explain his inability to extract meaning from relatively simple english sentences.
With malaprops like 'subsumes' etc. above, one wonders whether Selzer is really Daman Wayans just pulling our legs. Received on Sun Jul 30 2006 - 21:44:09 CEST