Re: MV Keys

"Jon Heggland" <heggland_at_idi.ntnu.no> wrote in message news:MPG.1e6fa30f17a25f9598976d_at_news.ntnu.no...
> In article <3bla025sc4m8u59a7qoc09bipjtnh5tmuk_at_4ax.com>,
> invalid_at_bigfoot.com says...
>> I don't agree with this. Strings are (IMHO) scalar types because they
>> can be sorted.
>
> Anything can be sorted. You just have to define an order. The order of
> strings is essentially arbitrary, and you can sort lists of characters
> the same way you sort strings.
>
>> However, mathematical operations on them, except for
>> comparison operators, are not possible. But there are other
>> operations, such as concatenation and substring, which are.
>
> What is a mathematical operation, and why are they important in this
> context? Any list can support concatenation and "subbing"---what point
> are you trying to make?
>
>> Also, the characters by themselves are meaningless much as the bits in
>> a number by themselves are meaningless. It is the order of the bits,
>> and the order of the characters, that give the number or string any
>> meaning. Therefore, if you consider VARCHAR to be a compound type, you
>> would have to say that DECIMAL is, too. And with real compound types
>> such as lists or arrays, it is the elements themselves, and not the
>> collection of elements, which gives the type semantic meaning.
>
> I'd say the meaning is primarily in the mind of the human using the
> system. But I agree(?) that DECIMAL may indeed be considered compound. I
> can use an int32 as an array of bits, each bit with a "meaning" in
> itself---and I can likewise use a string as an array of characters. It
> is just a matter of perspective, of mindset. The computer can't tell the
> difference.
>
>> But I'm not a mathematician, so I couldn't say what it takes to prove
>> whether something is a scalar type or not. Is there a formal
>> definition?
>
> Exactly my question. I don't think there can be, but I may be wrong. :)

Doesn't the determination of whether a type is scalar or not depend upon the universe of discourse? I think that a string is a scalar if any of the following statements hold: (1) individual character values don't belong to the universe of discourse, (2) the meaning of the individual character values aren't directly augmented by the attribute name, (3) the meaning of the individual character values aren't augmented by their position in the list, or (4) it is only the permutation of character values that has meaning with respect to the containing relation. For example, the elements in a list of birth dates aren't just dates, they're birth dates; the numbers in a coordinate aren't just numbers, they're longitude and lattitude. I think that some of those properties could be applied to other types as well, though I can't think of an example just now.

> --
> Jon
Received on Wed Mar 01 2006 - 13:45:26 CET