Re: RM and abstract syntax trees
Date: Tue, 13 Nov 2007 17:19:00 -0400
Ed Prochak wrote:
> On Nov 12, 9:42 pm, paul c <toledobythe..._at_ooyah.ac> wrote:
>>Pointers of either kind are nothing more than implementation devices >>when it comes to the RM. I'm even getting the impression that some >>people think a data design that involves surrogate attributes must >>involve pointers.
> No I am saying that too many new Relational Database developeres treat
> surrogate attributes as if they were pointers.
>> This seems to imply that those are the only kind of >>attributes that could do that whereas I would say that as far as the RM >>is concerned, no attributes are ever equivalent to pointers. If one is >>using a dbms that has a feature to generate keys, I don't see why one >>would take that to be a relational feature, don't see why a logical data >>design needs pointers in the first place, don't see what surrogates have >>to do with the RM, don't see what lazy instant gratification has to do >>with logical data design, blah, blah, blah.
> You nailed it, "lazy instant gratification".
> Surrogates do come into RM at the higher normalization levels, I
> Can one of the knowledgable theorists correct me here?
"Surrogates" have nothing to do with normalization. The design criteria for keys are: uniqueness, irreducibility, simplicity, stability and familiarity. Sometimes the criteria conflict requiring design tradeoffs.
A lot of developers ignore familiarity as a criterion. Regardless whether one adds an extra numeric attribute as an arbitrary key, one needs to declare all candidate keys to the dbms, or the dbms cannot manage integrity. Received on Tue Nov 13 2007 - 22:19:00 CET