Technical report --- negated knowledge and inconsistency

[Lokendra Shastri]

        Dealing with negated knowledge and inconsistency in a neurally
	motivated model of memory and reflexive reasoning.

        Lokendra Shastri and Dean J. Grannes
        TR-95-041
	ICSI
        August 1995

	Recently, SHRUTI has been proposed as a connectionist model of
	rapid reasoning. It demonstrates how a network of simple neuron-
	like elements can encode a large number of specific facts as well
	as systematic knowledge (rules) involving n-ary relations, quanti-
	fication and concept hierarchies, and perform a class of reasoning
	with extreme efficiency. The model, however, does not deal with
	negated facts and rules involving negated antecedents and 
	consequents. We describe an extension of SHRUTI that can encode
	positive as well as negated knowledge and use such knowledge
	during reflexive reasoning. The extended model explains how an
	agent can hold inconsistent knowledge in its long-term memory
	without being ``aware'' that its beliefs are inconsistent, but
	detect a contradiction whenever inconsistent beliefs that are 
	within a certain inferential distance of each other become 
	co-active during an episode of reasoning. Thus the model is not
	logically omniscient, but detects contradictions whenever it tries 
	to use inconsistent knowledge. The extended model also explains how
	limited attentional focus or action under time pressure can lead an
	agent to produce an erroneous response.  A biologically signficant
	feature of the model is that it uses  only local inhibition to
	encode negated knowledge. Like the basic model, the extended model
	encodes and propagates dynamic bindings using temporal synchrony.

	Key Words: long-term memory; rapid reasoning; dynamic bindings;
		   synchrony; knowledge representation; neural oscillations;
		   short-term memory; negation; inconsistent knowledge.


ftp-server:	ftp.icsi.berkeley.edu (128.32.201.55)
ftp-file:	/pub/techreports/1995/tr-95-041.ps.Z


Lokendra Shastri
International Computer Science Institute
1947 Center Street, Suite 600
Berkeley, CA 94704
http://www.icsi.berkeley.edu/~shastri

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