Re: So what's null then if it's not nothing?

On Thu, 24 Nov 2005 09:49:46 +0200, x wrote:

(snip)
>Then how do you distinguish among Objects that are known to have no Color
>and Objects that have an unknown Color ?

Hi x,

If it's relevant to distinguish, then it has to be part of the data model.

If a certain type of objects is known never to have a color, then this has to be done with a subtype - the color attribute should only be present on the subtypes that can have a color.

If it's not related to object type but only to specific objects and the distinction between "known not to have a color" or "color unknown" is relevant, then there as to be an attribute "reason of color absense".

Best, Hugo

-- 

(Remove _NO_ and _SPAM_ to get my e-mail address)