Re: Normalisation

Jon Heggland wrote:
> In article <iCCxe.135818$lx6.7272566_at_phobos.telenet-ops.be>,
> jan.hidders_at_REMOVETHIS.pandora.be says...
>

>>>Well, the "atomicity" definition doesn't hold up under scrutiny, and the 
>>>"you shouldn't have more than one column about the same thing" 
>>>definition is too informal.
>>
>>Yeah, that's what Date claims. Many disagree, including me.

Roughly, I would say that it means that all your data manipulation can be expressed as operations over a signature that consists only of (1) domains described by an abstract data type and (2) relations that contain in their fields only values from these domains.

An unnest operation, for example, cannot be described in that way.

• Jan Hidders