From: Julie Letchner (letchner_at_cs.washington.edu)
Date: Tue Oct 21 2003 - 16:03:56 PDT
Authors: Jon Doyle, Ramesh Patil
The fundamental theme of the paper is the tradeoff between the expressivity
of a language, and the performance-in terms of efficiency, soundness, and
completeness-that it can guarantee. The authors explore this theme in the
context of an argument favoring expressivity over guarantees.
The first part of the argument is that KL-ONE-derived systems are too
restrictive to be general-purpose. The authors present various examples of
situations in which this is the case. While none of their examples are
surprises, an encompassing list of the limitations of contemporary systems
was probably valuable in 1991 as a tool for motivating a change in the
philosophy underlying the development of these systems.
The second part of the argument is that a new philosophy emphasizing
generality over performance guarantees is both justified and beneficial.
The author's arguments here are pretty common-sense, and while this may not
have been the first time that such a design philosophy had been proposed, I
think that the direct feature-by-feature comparison of system was clear and
powerful (though a bit lengthy!), and probably reached more KR people than a
stand-alone paper on the virtues of generality-based systems would have.
It seems that the KL-ONE-derived systems were the standard when this paper
was published, which makes this presentation of an alternate approach
valuable.
I think the biggest flaw in the paper is its relative one-sidedness. The
authors explain the limitations of one system and propose their own to cope
with these limitations, but they don't address the obvious fact that the
system they propose has obvious limits. The paper would have been more
powerful as a presentation of two ends of a spectrum, instead of an argument
for the basic superiority of one end over the other.
Another major problem I had with the paper was its organization; it was long
and repetitive, and included more detail than was necessary to get the point
across. I think it could have been more appropriately divided into two
papers: one discussing the basic tradeoffs of KR system design, and the
other exploring this tradeoff in a neutral comparison of the two systems
described.
Finally, the paper made it clear that we need a way to formalize the
effectiveness of a KR system. It could be either a single effectiveness
measurement, or a multi-faceted evaluation that determines effectiveness
over several axes such as computational efficiency, expressivity, cost to
the user/developer, etc. Without a concrete method of evaluation, the
debate in this paper will see no resolution. More importantly, the reality
is that both extremes of the spectrum have potential applications in the
real world, and a concrete evaluation method will allow users to choose the
KR system most appropriate to their situation.
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