Re: Trying to define Surrogates

Brian Selzer wrote:
> "David Cressey" <dcressey_at_verizon.net> wrote in message
> news:KShGg.1199$HW1.451_at_trndny03...
>

>>"Brian Selzer" <brian_at_selzer-software.com> wrote in message
>>news:760Gg.9898$1f6.4300_at_newssvr27.news.prodigy.net...
>>
>>>I've changed my position.  I just had a revelation that the need for key
>>>stability is a symptom of the problem, not the problem itself.  I still
>>>think that the model has a problem, but the root cause has nothing to do
>>>with how stable a key is: rather, it is that there isn't a mechanism
>>
>>defined
>>
>>>in the model to correlate tuples during an update.  I posted in the other
>>>thread the line of thinking that led to this revelation, but I'm going to
>>>repost, so that others who are not following that thread can comment. 
>>>I'm
>>>going to use the subject "Relation Schemata vs. Relation Variables" if
>>
>>you'd
>>
>>>like to follow it.
>>
>>
>>The minute you start "correlating tuples" instead of correlating the 
>>things
>>the data describes  you are starting down the path of reducing the RDM to
>>the GDM.  (graph data model).  Tuples aren't correlated.  Data items are.
>>

Uh... How many types of co-relation can you think of? One? The appearance-not-identity-changing correlation? Are there also identity-not-appearance-changing corrrelations? The astute would name +A+I corrrrelation and -A-I corrrrrelation, too! (Don't want to waste any opportunities)

Of course, a different set of rules control things when tuples /CAN NOT/ be correlated, wouldn't you say?

  There are
> two ways to be sure that something that you talked about before a change is
> the same as what you're talking about now.

[Not if you're doing the talking...]

   One is to choose a set of
> identifying properties of the thing that you can be certain will remain
> constant throughout the change, and the other is to observe it throughout
> the change, noting how it changed. In the context of a database, you can
> choose identifying properties of each thing that are certain to remain
> constant throughout the change and reference them in the facts about the
> thing, or you can observe the things that are changing, noting how each
> changed.

Uh... Are you sure there are two alternatives? Which is it? How would you know? Received on Tue Aug 22 2006 - 03:14:25 CEST