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Re: defaults

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 23 Jan 2002 07:31:32 -0500
To: hendler@cs.umd.edu
Cc: las@olin.edu, Frank.van.Harmelen@cs.vu.nl, www-webont-wg@w3.org
Message-Id: <20020123073132X.pfps@research.bell-labs.com>
From: Jim Hendler <hendler@cs.umd.edu>
Subject: Re: defaults
Date: Tue, 22 Jan 2002 22:04:07 -0500

> At 4:23 PM -0500 1/22/02, Lynn Andrea Stein wrote:
> >I believe that we will have a difficult if not impossible time in
> >producing a "reasonable" default mechanism.

[...]

> The overwhelming "anti-default" span of this discussion forces me to 
> mention that the "other half" of the KR world (the frames folks) have 
> never had any real problem with defaults (or non-monotonicity). 

Hmm.  I seem to remember lots of problems with defaults in frames.


Taken from the Parka 3.2 Manual
(http://www.cs.umd.edu/projects/plus/Parka/parka3-manual.ps):

	A slot for predicate p is inherited only by frames which do not
	already have an explicit slot for p [even if p can have multiple
	values].  [p. 19]

	If an inheritance conflict cannot be resolved [because Parka's
	inferential distance ordering algorithm computes identical numbers
	for multiple inheritable frames], Parka randomly chooses one of the
	frames to inherit the slot from. [p. 19]

In Parka, as far as I can tell, all frame-specified slot information for
slots that inherit using IDO inheritance can be overridden.


I would not call this problem-free by any stretch of the imagination.


peter
Received on Wednesday, 23 January 2002 07:31:53 GMT

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