Date: Wed, 31 Oct 2007 19:58:59 GMT
Bob Badour wrote:
> paul c wrote:
>> David BL wrote: >> >>> On Oct 31, 4:31 pm, "Roy Hann" <specia..._at_processed.almost.meat> >> >> ... >> >>>> 1NF does not *require* that values be atomic. It asserts that >>>> values will >>>> be *treated as* atomic. Big difference. Essential difference. >>>> >>>> Roy >>> >>> Can that be formalised? I agree with Bob that in general we have a >>> set of operators and they can allow us to see internal structure. >>> What does it mean for a value to be *treated* as atomic? >> >> I think it means that relational algebra operators are not allowed to >> decompose it.
> Actually, the structure is illusory and representation-dependent.
> Domains have operations that appear to reveal internal structure even
> when that internal structure may not physically exist.
Okay, maybe it's clearer to say that relational algebra operators don't decompose (attribute) values.
(There might be operators that do decompose, eg., aggregate operators, but they aren't part of the essential algebra. Also, I think decomposing a representation structure is quite different from decomposing a value. I was trying to say that I think the relops don't do either.) Received on Wed Oct 31 2007 - 20:58:59 CET