From: Lucas Kreger-Stickles (lucasks_at_cs.washington.edu)
Date: Wed Oct 22 2003 - 10:58:53 PDT
Lucas Kreger-Stickles
Paper: Two Theses of Knowledge Representation / Doyle and Patil
Summary: Doyle and Patil explore the trade-off between efficiency and
expressibility in knowledge based systems, arguing that languages should
not be restricted in the quest for guaranteed polynomial execution but
rather a general purpose system should allow the user to selectively
request information within certain constraints of completeness and runtime.
Most Important Ideas:
*There is a trade off between efficiency and expressibility and this
trade off should be left for the user (not the system designer ) to
decide.
The authors argue that when the system designer determines this trade
off it makes so many ideas inexpressible that it defeats the purpose of
the system. Essentially, the restrictions don't force the programmer to
say what they were going to say in a better way, but instead make it so
they can't say it at all.
*Classification and worst case run time are not the most accurate
measures of the viability of a system.
The authors argue that classification is only one operation performed by
a system and that system performance depends on "the complete mix of
operations performed". Furthermore they suggest that certain systems do
not need 100% accuracy nor do they need worst case bounded performance.
They argue that the success of a system should be determined by its
utility given the function it must perform and this is the true behavior
of a 'rational' agent or system.
Largest Flaws:
*The authors indicate that for knowledge bases, the decisions about
which constructs to use should be left to the programmer, arguing that
"what works best is for programmers to know when they are using a
dangerous construct." However, they make no attempt to address how
difficult it is to know when a construct is 'dangerous'. Furthermore,
they spend so much of their paper arguing that 'dangerous' constructs
are the most intuitive (or only) way of describing certain information
that it seems clear that a programmer given the choice could abuse their
freedom.
*They don't in anyway address the feasibility of their 'solution' to the
problem of general purpose knowledge base systems. This is
particularily troublesome in that they indicate that a systems
performance depends on all the operations that it performs. Clearly such
an augmentation would be difficult to encode and would incur significant
runtime overhead, therefore making it an impractical solution for
'critical' applications.
Open Research Questions:
*Could a system such as the one which the authors propose (a 'librarian'
type knowledge base) be constructed, which is actually helpful and for
which the overhead is not prohibitive?
*What are some other solutions to the trade off between efficiency and
expressibility?
This archive was generated by hypermail 2.1.6 : Wed Oct 22 2003 - 10:58:53 PDT