comments on the BLD proposal

Hi list members,

I would like to add a few comments/questions on the BLD spec.

My interest in RIF is mostly driven by my implementation work, and in
particular
by my current interest in using expressive KBs in relational databases. I am
considering using
RIF BLD as one of the input languages in a query answering system. This is a
prelude, just to describe
my angle of view on the subject.


(1) First of all, I would like to say a word in support of the inclusion of
(RHS) equalities.
This is one of the features that makes RIF BLD useful and interesting for my
work.
Without it, it would be a rather weak alternative to, e.g., SWRL. Perhaps,
my case is not unique.
I also have some practical experience with knowledge engineering with
FOL-based
formalisms, and one of the lessons is that without equality, possibly
restricted,
it can become quite painful.

(2) The current spec of the frame semantics is really confusing me.  The
condition on I_{frame} (in 3.2) creates a very strong
impression that o[a->b a->b] will not be equivalent to o[a->b] and, in
general, o[a->b c->d] will not
be equivalent to o[a->b] & o[c->d]. However, in 3.4 TVal_I on frames
respects the latter property.

(3) Use case 4.2 in http://www.w3.org/TR/2008/WD-rif-ucr-20080730/ uses
frames as (individual-valued) base terms.
The BLD spec does not seem to provide either syntax or semantics for such
use. Does it mean that such use was
considered initially but didn't make it to the spec?

(4) In general, it would be extremely helpful (to me as an implementer) to
see a reference translation to FOL.
IMHO, the standard would be the right place for it.

(5) Minor thing: isn't External(c) a well-formed (base) term when c is a
constant?


Thanks in advance for any help on (1)-(4).


Finally, thanks to the BLD team for doing an overall good job and good luck
with passing
the standartisation formalities!

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Dr. Alexandre Riazanov (Alexander Ryazanov)
Montreal, Canada
cell: +1 - 514 - 961 86 89
http://www.freewebs.com/riazanov/
http://www.linkedin.com/in/riazanov
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