Re: Modelling Disjoint Subtypes

"Marshall" <marshall.spight_at_gmail.com> wrote in news:1174761278.831402.100630_at_y66g2000hsf.googlegroups.com:

> On Mar 24, 9:04 am, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:
>>

>> In other words,  under what circumstances,  other than an attempt to
>> emulate object oriented viewpoint,  "R <x, y>; R1 <super R, z>; R2
>> <super R, w>" is 'better' than just "R1<x,y,z>, R2<x,y,w>" ?  What is
>> achieved by such decomposition ?  Clearly,  there is no data
>> redundancy because R1 and R2 are disjoint !

When I said "because R1 and R2 are disjoint", I implied that there is a constraint of course, e.g.: "R1 join R2 is_empty" or similar, as there would be with the three relvars !. Having dealt with that diversion, back to the original question: "under what circumstances, other than an attempt to emulate object oriented viewpoint, "R <x, y>; R1 <super R, z>; R2 <super R, w>" is 'better' than just "R1<x,y,z>, R2<x,y,w>" ? What is achieved by such decomposition ?"

I am not sure I understand the relevancy of your appeal to functional and OOP point of view.

> Nothing stops us from doing:
>
> insert R1(x, y, z) (1,1,1);
> insert R2(x, y, w) (1, 1, 1);
>
>
> Marshall
>
Received on Sat Mar 24 2007 - 20:26:16 CET