I ndexi ng strategi es for goal speci fi c retri eval of cases M i chael J. Pazzani D epar tm ent of I nfor m ati on and Com puter Sci ence U ni versi ty of Cal i forni a, I rvi ne, CA 92717 pazzani @ i cs. uci . edu O ne of the m ost curi ous features of the hi story of econom i c sancti ons has been the the extent to w hi ch the exper i ence of past cases has been overl ooked or i gnored- - Robi n Renw i ck 1 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
O utl i ne I . Probl em : retri eval of i ndi vi dual cases for m ul ti pl e purposes A . Expl anati on B. Predi cti on I I . W hy i ndexi ng i s the ri ght w ay to thi nk about retri eval A . Psychol ogi cal - 1. Reconstructi ve m em ory 2. Encodi ng speci fi ci ty & l evel s of processi ng B. Com putati onal Retri evi ng rel evant rather than si m i l ar cases I I I . I ndexi ng strategi es for goal speci fi c retri eval of cases A . Retri eval of i ndi vi dual and general i zed cases 1. Type of pr ocessi ng done at stor age ti m e 2. Content of retri eval cue 3. G oal of retri eval B. I ndi ces 1. Surface (rather than abstract) features 2. Strategi c goal (expl ai n vs. predi ct) 3. Featur e to be expl ai ned or pr edi cted 2 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
Question: What would happen if the United States refused to sell computers to South Korea unless South Korea stopped exporting automobiles to Canada? OCCAM 1 : The goal of the United States that South Korea not sell automobiles to Canada will fail and South Korea will purchase computers from a country which exports computers. This happened when the United States did not sell grain to the Soviet Union after the Soviet Union invaded Afghanistan. Argentina sold grain to the Soviet Union. Also, Australia did not sell uranium to France after France exploded nuclear weapons in the South Pacific. South Africa sold uranium to France. 1. O CCA M ’ s output i s edi ted sl i ghtl y, by addi ng tense i nf or m ati on to ver bs. 3 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
Question: What would the United States do if Turkey invaded Cyprus? OCCAM : The United States would refuse to sell a commodity to Turkey if Turkey invaded Cyprus. This happened when Greece invaded Bulgaria. The League of Nations refused to sell food to Greece. Also, when the Soviet Union invaded Afghanistan, the United States refused to sell grain to the Soviet Union. 4 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
W hy i ndexi ng i s the ri ght w ay to thi nk about retri eval : Reconstructi ve m em ory (Bartl ett, 1932; Schank 1980; Kol odner 1984) • A case i s organi zed i n m em ory by the know l edge structures that gui ded the com pr ehensi on of case. Corol l ary: A case w i l l be i ndexed i n m ul ti pl e pl aces i f m ore than one know l edge structure i s accessed duri ng com prehensi on • O nl y those aspects of a case w hi ch di ffer from those of the know l edge structure used for com prehensi on are stored. D i fferi ng features becom e i ndi ces that al l ow retri eval of the case w hen that feature i s present i n the retri eval cue (or i nferred from i nform ati on i n the retri eval cue) • A s m ore cases are added to m em ory, addi ti onal know l edge structures are created to organi ze new experi ences. 5 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
W hy i ndexi ng i s the ri ght w ay to thi nk about retri eval : Experi m ental Evi dence •Sem anti c m em ory (Freedm an & Loftus, 1971) Categor y (e. g. vegetabl e) & attr i bute (e. g. , gr een) Subj ects presented w i th category before attri bute retri eve exem pl ar m ore rapi dl y than attri bute before category. • Epi sodi c M em ory (Rei ser, Bl ack & A bel son, 1987) A cti vi ty (e. g. Eati ng at a Restaurant) & acti on (di dn’ t get w hat you w ant) Subj ects presented w i th acti vi ty before acti on retri eve exem pl ar m ore rapi dl y than acti on before acti vi ty. 6 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
The effect of processi ng task • Level s of processi ng (Crai k & Lockhart, 1972) Retri evabi l i ty affected by depth of processi ng duri ng storage Jacoby & D al l as (1981): Subj ects study w ord l i st: Subj ects answ er questi on 1. A ppearance: I s i t i n capi tal l etters 2. Sound: D oes i t rhym e w i th “teach” 3. M eani ng: I s i t a form of com m uni cati on I n test phase: subj ects veri fy that they studi ed w ord. Success Rate: M eani ng 50% < Sound 63% < M eani ng 86% • Encodi ng Speci fi ci ty (Tul vi ng, 1983) Retri eval affected by si m i l ari ty betw een storage and retri eval context Recogni ti on fai l ure of recal l abl e w ords. Sei fert (1988) found pri m i ng of story recal l rel ated to processi ng goal at storage and retri eval 7 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
W hy i ndexi ng i s the ri ght w ay to i m pl em ent CBR: Retri eve the m ost rel evant rather than the m ost si m i l ar case • A n i ndex i s a feature of a case i denti fi ed at storage ti m e that descri bes the si tuati ons i n w hi ch the case shoul d be retri eved. • Proposal s by W al tz and Thagard & H ol yoak cannot account for si tuati ons i n w hi ch there i s a uni que i tem speci fi ed by the retri eval cue i n m em ory, but i t i s not retri eved. “Can you thi nk of an i nci dent i n w hi ch the US threatened a thi rd-w orl d country and a U S adversary hel ped out?” “Can you thi nk of an i nci dent i n w hi ch an Engl i sh speaki ng country threatened an A fri can country and a country that exports pal l adi um hel ped out?” • Proposal by W al tz assum es that the m em ory processes cannot di sti ngui sh m ost si m i l ar case (accordi ng to the surface features) from the m ost rel evant. 8 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
Experi m ental Com pari son of nearest nei ghbor vs. EBL I nput: D escri pti on of 10 or 15 econom i c sancti ons i nci dents. Test: Predi ct success/fai l ure of fi ve hypotheti cal i nci dents. 100 A ccuracy 90 EBI 80 N earest 70 60 50 0 5 10 15 N um ber of Exam pl es 1961 USSR vs. Albania 1976 US vs. Ethiopia threat: Refuse to sell grain threat: Stop aid (57 million) demand: Stop economic ties with China demand: Stop human rights violations outcome: (fail) China sells Albania outcome: (fail) Soviets provide aid Canadian wheat at lower price 1980 US vs. USSR 1983 Australia vs. France threat: Cut off grain sales threat: Not sell uranium demand: Withdraw troops from demand: Stop nuclear tests Afghanistan outcome: (fail) France buys from outcome: (failure) Buy grain from South Africa at higher price Argentina at a higher price 9 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
W hat m akes a good i ndex? I .Rel evant surface features A . H undred step rul e- D eep f eatur es (e. g. , m or al s) cannot be com puted i n ti m e B. “M oral s and effects are the outputs of the retri eval process, not i ts i nputs” C. Rel evant surface features are those surface features that al l ow the sol uti on to a probl em to be i nferred. I I . A feature rel evant for one task m ay not be rel evant for a di fferent task. Processi ng task at storage ti m e becom es part of i ndex A . Expl anatory I ndi ces “What could cause the price of oil to rise?” B. Predi cti ve I ndi ces “What would happen if the US refused to sell com- puters to South Korea if South Korea continues to export automobiles to Canada?” 10 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
W hat m akes a good i ndex? I I I . D i fferent features of the sam e case can be expl ai ned or pr edi cted. The featur e that needs to be expl ai ned or pr edi cted becom es par t of the i ndex. A . Predi cti ng the resul t of an acti on What would happen if the United States refused to sell computers to South Korea unless South Korea stopped exporting automobiles to Canada? B. Predi cti ng w hat acti on w i l l occur What would the United States do if Turkey invaded Cyprus? Sum m ary: A n i ndex consi sts of a tri pl e • featur e and val ue of a case (or gener al i zed case) • descri pti on of task :explain or :predict • feature to be expl ai ned or predi cted. 11 Case Based Reasoni ng W orkshop M onday, M ay 29, 1989
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