Re: In an RDBMS, what does "Data" mean?

In message <QBpDc.122156$Sw.52192_at_attbi_s51>, Marshall Spight <mspight_at_dnai.com> writes
>"Anthony W. Youngman" <wol_at_thewolery.demon.co.uk> wrote in message news:1aPaN6Am2x0AFwN3_at_thewolery.demon.co.uk...
>>
>> Note that it's easy to go from a list to either of the other two. But in
>> order to go back, the set or bag needs to contain extra data (ie the
>> order) over the list.
>
>I don't see how you could consider that data "extra" if it was
>there originally.
>
>Anyway, the list [A, B, C] expressed as a set is { (1, A), (2, B), (3, C) }
>where [] denotes an ordered collection and {} denotes an unordered
>collection.

Well, you have just created a field called ORDER, and created the values 1, 2 and 3.

The point is that the data was NOT there initially - it was implicit. If something is implicit, then it quite clearly does not have existence in its own right.
>
>Going back to the list from the information-preserving set is not that hard.

Correct. But surely it's better to throw away the implicit ordering if it's unnecessary at the point of use, than to suddenly discover that it was necessary but that it's been thrown away by accident ... :-)

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
HEX wondered how much he should tell the Wizards. He felt it would not be a
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The Science of Discworld : (c) Terry Pratchett 1999