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M1/M4

M1/M4. CIS 479/579 Bruce R. Maxim UM-Dearborn. What is it?. Expert system shell for developing medium size applications Written in C/C++ Allows interface to external functions written in C/C++ and VB Allows access to database applications as well. Features. Symbolic Variables

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M1/M4

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  1. M1/M4 CIS 479/579 Bruce R. Maxim UM-Dearborn

  2. What is it? • Expert system shell for developing medium size applications • Written in C/C++ • Allows interface to external functions written in C/C++ and VB • Allows access to database applications as well

  3. Features • Symbolic Variables • Certainty factors • Backward chaining (mostly) • Limited forward chaining allowed (pre-suppositions) • Rule order used for conflict resolution • Cache (WM) manipulation allowed • Symbolic List processing • Debugging Environment • Explanation Facilities • Meta knowledge

  4. How does M1 find work? M1 seeks to determine values found in a goal or initialdata statement • Obtain value of expression computed by M1 • Look for value already in cache • Inference rules (searching and matching) • Prompts user for value if first 3 fail

  5. Examples • Goal statement goal = wine. • Initialdata statement initialdata = [preferred-color, preferred-body]. • Rule rule-5: if has-sauce = yes and sauce = cream then best-body = medium and best-body = full.

  6. Getting Started • You need copies of the files m1.exe and m1.cfg • You may find it helpful to examine the knowledge bases “wine”, “vine”, “cwine” • There is also an M1 Short Guide written by a former student posted on the course web page

  7. Syntax • Use lowercase for everything except variables • Identifiers begin with characters, may contain numbers and hyphens • To comment use /* */ • Rules can have multiple antecedents and make use of “and”, “or”, “not” • Rules can have multiple consequents

  8. Certainties • Similar to ad hoc approach described earlier -100 < CF < 100 100 completely certain 20 default threshold for true 0 neutral -100 completely false

  9. Certainties • If antecedents do not have an explicit CF if x = y then z = w cf 50 M1 uses 20 as threshold for truth of cache expression “x = y” and adds “z = w” to cache • If antecedents have explicit CF if x = y cf 30 then z = w cf 50 M1 uses 30 as threshold for truth of cache expression “x = y” and adde “z = w” to cache

  10. Certainties • What CF value is assigned to “z = w” ? • We take the product of the antecedent certainty and the rule certainties • If CF = 20 for “x = y” and CF = 50 in rule consequent then CF = (CF 20 * CF 50) = (0.2 * 0.5) = (0.1) = 10

  11. Certainties • For conjunction, use the minimum of all the antecedent CF values if x = y and a = b then z = w

  12. Certainties • For disjunction, we use the CF value of the antecedent that triggered the rule or the maximum of all antecedent CF values if x = y or a = b then z = w

  13. Meta-facts • Multivalued (needed with CF) multivalued(sauce). • Questions question(sauce) = 'What kind of sauce does the meal have?'. • Answers legalvals(sauce) = [spicy, sweet, cream]. • Automatic menu automaticmenu(sauce). • Enumerated answers enumeratedanswers(sauce).

  14. Meta-facts • Explanation rule-16: if the main component = poultry and has turkey = no then the best color = white cf 90 and the best color = red cf 30. explanation(rule-16) = [nl, 'For poultry dishes, I recommend white wines. Turkey, ', 'however, goes very well with some red wines.', nl].

  15. Wine has lots of similar rules rule-14: if best-body = light then recommended-body = light. rule-15: if best-body = medium then recommended-body = medium. rule-16: if best-body = full then recommended-body = full.

  16. Wine has lots of similar rules rule-21: if best-color = red then recommended-color = red. rule-22: if best-color = white then recommended-color = white.

  17. Wine has lots of similar rules rule-26: if best-sweetness = dry then recommended-sweetness = dry. rule-27: if best-sweetness = medium then recommended-sweetness = medium. rule-28: if best-sweetness = sweet then recommended-sweetness = sweet.

  18. Using variables in Vine we can replace 27 rules with these 3. v-rule-1: if best-X = V then recommended-X = V. v-rule-2: if best-X is unknown and preferred-X = V then recommended-X = V. v-rule-3: if best-X is unknown and preferred-X is unknown and default-X = V then recommended-X = V.

  19. Default values are used when M1 can’t find values noautomaticquestion(default-X). default-body = medium. default-color = red cf 50. default-color = white cf 50. default-sweetness = medium. • Sometimes we need to turn off automatic question generation to prevent user from entering values and allow M1 to skip searching the rule-base

  20. Wine has lots of specific rules rule-33: if recommended-color = red and recommended-body = medium and recommended-sweetness = medium or recommended-sweetness = sweet then wine = gamay.

  21. Vine makes use of tables to reduce number of rules multivalued(wine(COLOR,BODY,SWEETNESS)). v-rule-4: if recommended-color = C and recommended-body = B and recommended-sweetness = S and wine(C,B,S) = W then wine = W.

  22. Sample Table Entries wine(red,medium,medium) = gamay. wine(red,medium,sweet) = gamay. wine(white,light,dry) = chablis. wine(white,medium,dry) = 'sauvignon blanc'. wine(white,light,medium) = riesling. wine(white,light,sweet) = riesling. wine(white,medium,medium) = riesling. wine(white,medium,sweet) = riesling. wine(red,light,ANY) = valpolicella. wine(red,ANY,dry) = 'cabernet sauvignon'. wine(red,ANY,dry) = zinfandel. wine(red,ANY,medium) = 'cabernet sauvignon'. wine(red,ANY,medium) = zinfandel. wine(red,medium,medium) = 'pinot noir'. wine(red,full,ANY) = burgundy.

  23. Variable Scope • Variables restricted to the rule itself • M1 puts facts (e.g. recommended-color = preferred-color) in cache not values • This means we have to write v-rule-2: if best-X is unknown and preferred-X = V then recommended-X = V. and not bad-2: if best-color is unknown and then recommended-color = preferred-color.

  24. Comparing Numeric Facts • Correct if age N and N > 20 then category = adult. • Incorrect if age > 20 then category = adult.

  25. Arithmetic • Correct if distance = D and fare-mile = M and M * D = R then total-fare = R. • Incorrect total-fare = distance * fare-mile.

  26. Additional Features • User defined syntax lets you skip hyphens prefix best. prefix has. infix to. postfix ends. prefix main. infix with. prefix preferred. • Assigning string to identifier begin-message = [nl, nl, ‘hello’, nl, nl]. • Nocache prevents M1 from saving fact nocache(begin-message). • Presupostion presupposition(sauce) = has-sauce.

  27. Cwine initialdata = [begin the consultation, end the consultation ]. question(begin signal) = [nl,'Are you ready to begin the consultation (y/n)?']. legalvals(begin signal) = [yes,no]. rule-1: if begin message = M and display(M) and begin signal and display('\f') then begin the consultation. rule-2: if not begin signal and display("Issue 'go' command when ready to begin.") and do(abort) then begin the consultation.

  28. Cwine rule-3: if the wine for cycle N is known and user informed of selection N and user happy with selection N then consulting ends with cycle N. rule-4: if the wine for cycle N is unknown and display(['Sorry, not able to recommend any wines.', nl]) then consulting ends with cycle N. rule-5: if positiveinteger = I and consulting ends with cycle I and display([nl,nl,'The consultation is over.', nl]) then end the consultation.

  29. Cwine rule-30: if listof(the wine for cycle N) = [ONLYONE] and display([nl,'The best wine for this meal is ', ONLYONE, '.', nl,nl]) then the winelist for N is displayed. rule-31: if listof(X,ordered(the wine for cycle N) = X) = [ONE,TWO] and display([nl,'The best wines for this meal are ', ONE, ' and ', TWO, '.', nl,nl]) then the winelist for N is displayed.

  30. Cwine question(user happy with selection N) = ['Are you happy with these?']. legalvals(user happy with selection N) = [yes,no]. rule-33: if the description for N is given and the winelist for N is displayed then user informed of selection N.

  31. Cwine rule-9: if M > 1 and M - 1 = N then previouscycle to M = N. question(the new value for X for cycle N) = ['What ', X ,' would you prefer?']. legalvals(the new value for color for cycle N) = [red, white]. legalvals(the new value for body for cycle N) = [light, medium, full].

  32. Cwine legalvals(the new value for sweetness for cycle N) = [dry, medium, sweet]. automaticmenu(the new value for ANY for cycle N). enumeratedanswers(the new value for ANY for cycle N).

  33. Cwine rule-26: if previouscycle to M = N and not(the fault with cycle N = X) and the recommended X for cycle N = V then the recommended X for cycle M = V. rule-27: if previouscycle to M = N and the fault with cycle N = X and the new value for X for cycle M = V then the recommended X for cycle M = V.

  34. Cwine rule-28: if the recommended color for cycle N = C and the recommended body for cycle N = B and the recommended sweetness for cycle N = S and wine(C,B,S) = W then the wine for cycle N = W. rule-29: if the recommended color for cycle N = white and the recommended body for cycle N = full and feature = spiciness then the wine for cycle N = gewuerztraminer.

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