Re: object algebra

> > RDM (data expressed as collections of tuples contrained by the header,
> > etc) is less general than relational [ie ((((ab)cd)e)f)(gh)].
>
> What does that last thing represent? Is it some kind of s-expression
> syntax? So you're showing us a pair of trees and saying it's more
> general than relations? Why did you show a pair of trees when
> multiple heterogeneous trees are no more general than a single
> heterogeneous tree?

I was trying to express the flexibility offered by RDM vs relational algrebra.

RDM is like this:

Relation1
a b c d
z y m a
d f l NULL
d o q r

Relation2
a b c d e f g
z y m a v p m
d f l d l q NULL
d o q r z e p

Relational algebra (and TDM) is more like this:

a b
j
o m r u v l
q c
m z r

Do you see how RDM is "rectangularish" and incurs NULLs? Received on Thu Feb 26 2004 - 00:17:58 CET