Re: By The Dawn's Normal Light

From: Dawn M. Wolthuis <dwolt_at_tincat-group.comREMOVE>
Date: Sat, 23 Oct 2004 14:49:53 -0500
Message-ID: <clecle$p04$1_at_news.netins.net>


"Marshall Spight" <mspight_at_dnai.com> wrote in message news:ZMxed.303809$D%.296516_at_attbi_s51...
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message
news:clc0k2$ed1$1_at_news.netins.net...
> >
> > There are two types of collections -- "files" and "nested lists". The
> > nested lists may have one or more attribute types and zero to many
attribute
> > values. Whether the user cares about the ordering or not, the database
> > orders these, while the files are keyed, and therefore logically
ordered.
> > So, both top level structures (files) and their substructures are
logically
> > ordered.
>
> It's funny: the RM has no facilities for handling lists; the Pick model
> has no facilities for handling relations.

I'm not sure I would say it that way. Given that every Pick file has a single identified primary key (which may consist of multiple attributes), I guess that makes each file logically ordered, but you don't every access files (which resemble relations) by asking for the 4th one. The nested structures do have that operator, however.

> Sometimes you have ordered data, and sometimes you have unordered
> data. Which primitive operations you want depends on which one
> you have. Each model handles one well and ignores the other.
>
> I propose that the ideal model would handle both, and have
> relatively simple ways of transforming one into the other.

I'm in.

> Lists are simpler and sometimes therefore the better choice.
> Relations are more powerful, but that can mean more
> complexity than you need.

Functions are even more powerful -- you know you have a unique primary key that, effectively, maps to the remainder of the data for that, uh, record. I'm not sure what the current view of that is with relations, but I believe that each relation must have one or more (sets of) candidate keys. In that case, we can view them as functions as well, choosing one of the candidate key sets as the "from" and the remainder of the attributes as the "to". --dawn

>
> Marshall
>
>
Received on Sat Oct 23 2004 - 21:49:53 CEST

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