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Dynamic Memory. A Theory of Reminding and Learning in Computers and People - Schank R.C.

Schank R.C. Dynamic Memory. A Theory of Reminding and Learning in Computers and People - Cambridge University Press, 1982. - 250 p.
Download (direct link): dinamycmemory1982.djvu
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The final principle behind IPPís confidence scheme involves the treatment of spec-MOPs once they have been confirmed, i.e., an adequate amount of positive evidence has been accumulated to assume that the generalization represents the situation in the world. At this point the spec-MOP has the same status in memory as the S-MOPs that IPP starts with-it is permanent and cannot be deleted. Clearly this position is too strong, but it reflects the tendency of people to stick to the conclusions that they have made, unless there is overwhelming conflicting evidence.
Once a spec-MOP has been confirmed, it is effectively permanent.
This point cannot be illustrated as easily as the others. Intuitively, once a conclusion has been made, only a large amount of negative evidence, or some sort of logical explanation as to why the situation should have changed will alter that conclusion. A typical example would be a case in which when a very strong generalization had been made, such as concluding that the IRA carried out their attacks in Northern Ireland. Then a few minor anomalies, such as an attack in Germany by the IRA would do very little to undermine confidence in the generalization. Such stories would just be viewed as odd cases.
IPP can develop alternative models for situations in which spec-MOPS have been confirmed (for example, generalizing that many attacks in Northern Ireland are carried out by the Ulster Defense Regiment), but the confirmed generalization would still be available to explain relevant events. In effect, what IPP develops is a set of explanations, any one of which might accurately describe a specific story. When a story that fits more than one explanation is found, the predictions that can be made will be less certain, but they still represent the best possible information
Summary
We have seen that modification of long-term memory is an integral part of the text understanding process used by IPP. Such memory modification takes two basic forms. IPP makes generalizations by noticing similarities
Computer experiments
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among events and uses these generalizations as organizing points for its memory. In addition, as part of the understanding process, IPP constantly evaluates the validity of generalizations it has made, possibly leading to the abandonment of those that are not accurate representations of the world. A final point worth recalling about IPP is that it always interprets new input in terms of its generalization-based memory, and thus can display different behavior when processing the same story depending upon the state of its memory.
Knowledge-based self-organizing memory2
As new unanticipated items are added to a memory, it must be able to reorganize itself to maintain retrieval efficiency. CYRUS is a program that employs a knowledge-based memory reorganization scheme together with a fact retrieval system,
Given a new fact about former Secretaries of State Cyrus Vance or Edmund Muskie, CYRUS integrates it into its already-existing memory organization. It retrieves facts from its memory when queried in English. Following is a dialog with CYRUS:
Has Vance talked to Gromyko recently?
YES, MOST RECENTLY IN GENEVA IN DECEMBER.
Did he talk to him about SALT?
YES, FOR 5 HOURS,
When did he leave Geneva?
ON DECEMBER 24,
Initial memory organization
CYRUS uses structures called Episodic Memory Organization Packets (E-
MOPs). E-MOPs organize similar episodes according to their differences and keep track of their similarities (Kolodner, 1980; Schank, 1980). An E-MOP is a net in which each node is either an E-MOP or an event. Each E-MOP has two important aspects-(1) generalized information characterizing its episodes, and (2) tree-like structures that index its episodes by their differences. An E-MOPís norms include information describing its events, such as their usual participants, locations, and topics, and their usual relationships to other events.
An E-MOPís indices correspond to event features, and can index either
2 This section was written by Janet Kolodner It describes work that she did while she was a graduate student at Yale University, She is now an assistant professor at Georgia Institute of Technology, Department of Information and Computer Science
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Dynamic memory
(MOP 1)
Norms: The actor is Cyrus Vance
Participants are foreign diplomats Topics are international contracts Participants talked to each other Goal was to resolve disputed contract
Norms:
Differences: Participants
(3) Begin (MOP 2)
Participants include Begin Topic concerns Israel and Arabs Specialization of MOP1
Gromyko SALT
Norms:
Topic
(2) Jerusalem
EV 3
(4) Camp David Accords (MOP 3)
Topic is the CDA Participants are Israeli Specification of MOPl
Differences: Topic
Differences: Participants
í5) Jerusalem
(6) Camp David Accords (MOP 4)
(7) Begin (MOP 4)
(8) Dayan
I
EV 4
Figure 10
individual events or specialized E-MOPs. When an E-MOP holds only one episode with a particular feature, the corresponding index will point to the individual episode. When two or more episodes in an E-MOP share the same feature, its corresponding index will point to a specialized individual episode. When two or more episodes in an E-MOP share the same feature, its corresponding index will point to a specialized sub-MOP which organizes the events with that feature. In this way, MOP/sub-MOP hierarchies are formed. The MOP in Figure 10 is part of CYRUSí diplomatic meetings E-MOP
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