Re: re-post: comments on OWL 2 RL Profile (April 21 2009 public draft)

% followup note with comments on OWL 2 Profile, public draft of 2009-04-21
% by Benjamin Grosof, May 28, 2009
% in reply to Ian Horrocks reply on behalf of the W3C OWL Working Group of
%  May 18, 2009 to original comments note of May 12, 2009

Hi Ian, Boris, Zhe, and other OWL 2 Working group folks,

This is to follow up on Ian's reply of May 18 to my comments note of May 12.
Sorry for the delay in sending this, I've been really buried in work lately.

1. Regarding the semantics of rule systems, the text you added is
good, but I'd like to see it a bit more elaborated.  Here is some
suggested specific additional text to insert nearby, please:

- The semantics of most existing implemented rule systems is either
  based on, or equivalent to, or closer to, the declarative logic
  programs (LP) logical knowledge representation (KR) rather than FOL,
  when in the Horn case.  OWL 2 RL's expressiveness is roughly
  equivalent to a subset of Horn FOL.  For Horn FOL, there is a quite
  close semantic relationship to Horn LP.  See for example
  [<cite>[[#ref-Lloyd]]</cite>], especially section 6 (pp. 35-40).

  o ref-Lloyd:  Lloyd, J.W. Foundations of Logic Programming, 2nd ed.
                Springer-Verlag, Berlin, Germany, 1987.

2. Regarding establishing a mechanism for recognizing and naming useful
subsets of expressiveness, thanks for passing the suggestion on to the
Semantic Web Coordination Group.

- I recommend a process of 2-3 years in length, rather than of
  indefinite length, should be set up.  That could then be extended in
  length if it seems desirable later.

OWLED and future W3C submissions will also indeed be good venues.

5. Regarding the expressive restrictions in OWL, I suggest you briefly
indicate, where possible, the design rationale for them when that is
based on implementation rather than expressive considerations.  E.g.,
for reflexive object properties in particular.

Regarding the primer (3.) and the proof of theorem PR1 (4.), please just
informally encourage these to happen.

That's it.

Compliments on a quite good job overall.

Best,
Benjamin



Benjamin Grosof, PhD -- Semantic Technologies.
Sr. Research Program Manager, Vulcan Inc.
Head of Project Halo Advanced Research (HalAR) program.