Re: TRUE and FALSE values in the relational lattice

On Jun 19, 11:40 pm, Jon Heggland <jon.heggl..._at_idi.ntnu.no> wrote:
> Vadim Tropashko wrote:
> > As expected this expression is valued to 00 or 01, so Marshall was
> > eventually right when interpreting those relations as TRUE and FALSE.
>
> Not to disparage your contributions or anything, but hasn't the
> association between TABLE_DUM / 00 and FALSE, and TABLE_DEE / 01 and
> TRUE been known for many, many years?

Not sure who the "you" in "your" is here, but I figure it's either me or Vadim. Yes, in the regular relational algebra, the correspondence
has been known for years. In the relational lattice, it hasn't been established whether that's the best choice yet. In fact, it's not clear what the correspondence *means.* Note that various authors, such as Dijkstra and D&D (in TTM) advocate a dedicated two-valued boolean type, despite the correspondence. I've been thinking for a while that that may not be necessary; it may be sufficient just to use DEE (aka 01) and some other value, either 00 or 10 depending on when you ask me. :-)

Marshall Received on Thu Jun 21 2007 - 06:21:21 CEST