Subject: Re: [lojban] Re: zil

From: John Cowan <[email-masked]>
Date: Thu, 17 Oct 2002 15:29:06 -0400 (EDT)

Jorge Llambias scripsit:

> This serves as a superficial analogy, but it's not quite the same thing.
> zi'o expands the meaning of a selbri, a projection doesn't. A projection
> just fixes the value of one of the arguments, or restricts in some way
> the relationship between the arguments. zi'o goes the other way.

By my understanding, what you are calling a projection is really a selection
followed by a projection. Projection as such just shrinks the number of
domains in the relation. The reason why new tuples can then appear in the
Lojban context is because Lojban is an open world, where new relationships
can appear from thin air, whereas implementations of relational algebra
are closed worlds, where the tuples that initially exist are all the ones
that will ever exist unless they are explicitly added.

-- 
John Cowan <[email-masked]> 
http://www.reutershealth.com http://www.ccil.org/~cowan
Yakka foob mog. Grug pubbawup zink wattoom gazork. Chumble spuzz.
-- Calvin, giving Newton's First Law "in his own words"