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Home -> Community -> Usenet -> comp.databases.theory -> Re: Stored fields ordered left to right
"Marshall Spight" <mspight_at_dnai.com> wrote in message
news:LaJHb.687449$Fm2.593735_at_attbi_s04...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
news:ON6dnTDvsbMQAHOiRVn-hg_at_golden.net...
> >
> > Mathematical relations do not rely on attribute order. The physical
> > representation of mathematical relations using written symbols on planar
> > surfaces conventionally uses attribute order for succinctness.
>
> This doesn't seem correct to me.
>
> Consider the union of two sets of ordered pairs:
>
> { (1,2) }
> union
> { (2,1) }
>
> The union of those sets is a set with two elements, yes? How
> are we distinguishing between (1,2) and (2,1) if not by order?
The order is implicit in the physical representation.
> Is there some hidden information?
Yes. The semantics of the pairs. Why is the first one { (1,2) } and not { (2,1) } ?
The order in which we choose to list the dimensions is entirely arbitrary. Received on Sun Dec 28 2003 - 23:25:17 CST