Re: MV Keys

"Jon Heggland" <heggland_at_idi.ntnu.no> wrote in message news:MPG.1e720c9612b942ff98977d_at_news.ntnu.no...
> In article <GHgNf.26120$_S7.24277_at_newssvr14.news.prodigy.com>,
> brian_at_selzer-software.com says...
>> Doesn't the determination of whether a type is scalar or not depend upon
>> the
>> universe of discourse?
>
> In that case, scalar-ness is not a property of a type, but a property of
> the use of a type in a certain context. I'd say that severely reduces
> the usefulness of the concept (if it *has* any usefulness to begin
> with:).
>

I don't see it that way. If you can talk intelligently about values that are contained in a list apart from that list within the constraints imposed by the universe, then the list is not atomic or scalar with respect to the universe of discourse. The list can be resolved into components that have meaning with respect to the universe independent of the list.

>> 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;
>
> Speaking of dates, is date a scalar type? Its components (year, month,
> day) do belong to the universe of discourse in most cases.

Absolutely. Year, month and day are not components, they're transformations. Time is a continuum, and dates are points along that continuum. Year, month and day are functions of the number of days that have passed since a widely accepted point in time.

> --
> Jon
Received on Fri Mar 03 2006 - 11:21:16 CET