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Re: repeating groups

From: Jon Heggland <heggland_at_idi.ntnu.no>
Date: Mon, 20 Feb 2006 08:28:11 +0100
Message-ID: <MPG.1e638df9eab10b65989767@news.ntnu.no>


In article <1140329504.824686.293790_at_o13g2000cwo.googlegroups.com>, marshall.spight_at_gmail.com says...
> Jonathan Leffler wrote:
> > mAsterdam wrote:
> > > Marshall Spight wrote:
> > >>>[...snippage...]
> > >> Sure. But there are several ways out of the repeating groups problem
> > >>
> > >> 1) decomposing relations, aka "classical" 1NF
> > >> 2) higher-than-1 cardinality attributes: lists or sets
> > >
> > > Aren't you jumping over the "order may have meaning" problem
> > > here by taking these two together?
> >
> > It depends whether you take the OR in 'lists or sets' to be inclusive or
> > exclusive, doesn't it? If it is inclusive, then lists handle the 'order
> > has meaning' case and sets handle the 'order is not significant case'.
> > But you've complicated the algebra - instead of just sets, you've now
> > got to deal with lists and sets (and the alternatives you list below).
>
> Yes, *exactly*!
>
> Complicating the algebra should give us pause, but I now believe
> it is something that we have to do.

Can anybody please take half a minute to explain to a poor ignoramus why list attributes affects the (relational, I assume(?)) algebra? It seems to be taken for granted around here, but I can't figure out how/why. What am I missing?

-- 
Jon
Received on Mon Feb 20 2006 - 01:28:11 CST

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