(a) Write a brief note on ‘Episodic Memory Organization Packets’ (E-MOPS)

Roger Schank and his students at Yale University have developed several computer systems which perform different functions related to the use of natural language, text, knowledge representation, and memory organization. One system of particular interest was developed by Janet Kolodner (1983a, 1983b, 1984) to study problems associated with the retrieval and organization of reconstructive memory. Her system, called CYRUS (Computerized Yale Retrieval and Updating System) stores episodes from the lives of former secretaries of state Cyrus Vance and Edmund Muskie. The episodes are indexed and stored in long-term memory for subsequent use in answering queries posted in English. The system has many of the other features.

The basic memory model in CYRUS is a network consisting of Episodie Memory Organization Packets (E-MOPs). Each such E-MOP is a frame-like node structure which contains conceptual information related to different categories of episodic events. E-MOPs are indexed in memory by one or more distinguishing features. For example, there are basic E-MOPs for diplomatic meetings with foreign dignitaries, specialized political conferences, traveling, sightseeing, negotiations, state dinners, as well as other basic events related to diplomatic state functions. The diplomatic-meeting E-MOP, called $MEET, contains information which is common to all diplomatic meeting events. The common information which characterizes such an E-MOP is called its content. For example, $MEET might contain the following information:

Actio : Cyrus Vance

Participants : foreign diplomats

Topics : international contracts

Actions : participants talk to each other

Goals : to resolve disputed contract

A second type of information contained in E-MOPs are the indices which index either individual episodes or other E-MOPs which have become specializations of their parent E-MOPs. For instance, specific diplomatic meetings are indexed by features unique to the individual meetings such as location, actual topic discussed, or the actual meeting participants. A typical $MEET E-MOP which has indices to two particular event meetings EV1 and EV2, is illustrated in following figure (b1).

 

Figure (b1) : An example of an EMOP with two indexed events EV1 and EV2

One of the meeting indexed was between Vance and Gromyko of the USSR in which they discussed SALT (arms limit talks). This is labeled as event EV1 in the figure. The second meeting was between Vance and Begin of Israel in which they discussed Arab-Israeli peace. This is labeled as event EV2. Note that each of these events can be accessed through more than one feature (index). For example peace, “through a participants’ nationality value of “Israel,” through a participants’ occupation value of “head of state,” and so on.

As new diplomatic meetings are entered into the system, they are either integrated with the $MEET E-MOP as a separately indexed event or merged with another event to form a new specialized meeting E-MOP. When several events belonging to the same MOP category are entered, common event features are used to generalize the E-MOP. This information is collected in the frame contents. Specialization may also be required when over-generalization has occurred. Thus, memory is continually being reorganized as new facts are entered. This process prevents the addition of excessive memory entries and much redundancy which would result if every event entered resulted in the addition of a separate event. Reorganization can also cause forgetting, since originally assigned indices may be changed when new structures are formed. When this occurs, an item cannot be located; so the system attempts to derive new indices from the context and through other indices by reconstructing related events.

To see how CYRUS builds and maintains a memory organization, we briefly examine how a basic E-MOP grows and undergoes revision with time. Initially, the $MEET E-MOP of Figure (b1) would consist of the content part of the frame only. Then, after a first meeting occurred, indices relevant and unique to that meeting are established and recorded, and pointers are set to the corresponding event. Subsequent meetings also result in the determination of new event indices, or, if two or more of the new meetings have some features in common, a new sub-E-MOP would be formed with indices established and pointers are set to the new E-MOP would be formed with indices established and pointers set to the new E-MOP. This process continues with new indices to events added or new E-MOPs formed and indexed as new meetings occur. Furthermore, the content portion of all E-MOPs is continually monitored and modified to better describe the common events it indexes. Thus generalized to include this property and new indices are determined. When over generalization occurs, subsequent events will result in a correction through some specialization and recomputation of indices.

After the two diplomatic meetings described above had been entered, indices are developed by the system to index the events (EV1 and EV2) using features which discriminate between the two meetings (figure b1). If a third meeting is now entered, say one between Vance and Sadat of Egype, which is also about Arab-Israeli peace, new E-MOPs will be formed sice this meeting has some features in common with the Begin (V1) meeting. One of the new E-MOPs that is formed is indexed under the previous topic index. It has the following structure.

The key issues in this type of organization are the same as those noted earlier. They are

(1) the selection and computation of good indices for new events so that similar events can be located in memory for new event integration.

(2) Monitoring and reorganization of memory to accommodate new events as they occur, and

(3) Access of the correct event information when provided clues for retrieval.

Associative Network of ‘Indira Gandhi National Open University’

'Episodic Memory Organization Packets’ (E-MOPS)

'Frame Problem’ in context of ‘Knowledge Organization and Management’.

Object description of ‘windshield wiper’ State what variable bindings , if any, will make the following lists match:

(?x *y a b c(d e))
and
(a (j k (f)) a b c *z)