Re: object algebra

> > Tables are not relations, and neither of them are "rectangular." You can
> > display, for example, a 4-dimensional tessaract (hypercube) as a table if
> > you like - that doesn't mean it's rectangular.
>
> You have to be prepared to forgive people at least a little for making
> this mistaken assumption.

I realize that things can be presented in mulitple formats regardless of how it is actually stored. For example XDb1's GUI presents things in tables, trees or sentences but the things themselve aren't stored that way. What I am saying is that the internal format of RDM is "rectangularish" and while it can also display things as tables, trees and sentences, it is clumsier at some things like trees compared to tables. TDM/XDb1's internal structure is more general and therefore more neutral to either. In fact RDM's "rectangularish" internal structure (aka relation) is the cause of NULLs. If one doubts that RDM's "rectangularish" relation makes it clumsy at trees, one might try to replicate the example shown at www.xdb1.com/Example/Ex076.asp

> - xBase was often described as a "relational database" despite the
> fact that it certainly wasn't;

All information systems are relational to some degree. RDM is simply one of the closest to pure relational algebra.

> - I haven't seen much evidence of commercial SQL system vendors
> having produced systems that are convenient to use with data
> that isn't shaped pretty blindly like a "table."

While XDb1 is only experimental, it does provide a way to manage things thru tables, trees and sentences.

> Perhaps a relational data representation _should_ be analagous to Lisp
> structures or Prolog facts, and therefore be able to be of pretty much
> any shape. But in the absence of conspicuous implementations of such,
> it shouldn't be surprising for people to make the "table" mistake...

XDb1 allows things of variable shapes to be entered via table, tree and english-like sentences. For example, the following sentences creates the equivalent of a relation with 2 tuples.

person isa thing.
john isa person.
mary isa person.

For more details, see www.xdb1.com/NLI/Default.asp and www.xdb1.com/Example/Ex001.asp Received on Wed Feb 25 2004 - 05:22:30 CET