Lab12

prolog

lab12/lab_1.pl

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+killer(butch).
+married(mia, marsellus).
+dead(zed).
+kills(marsellus,X):-footmassage(X,mia).
+loves(mia,X):-gooddancer(X).
+eats(jules,X):-nutritious(X); tasty(X).
+
+/**
+ * a. i. I built up the representations so that the nouns were consistently the
+ * arguments (butch,mia,marsellus), and if a variable was required then
+ * I would use X as a simple variable. The relational adjectives and verbs 
+ * were used as functors (married, kills, killer, eats). From there it was a 
+ * simple matter of determining which functors in regard to which arguments 
+ * implied which other functors in regard to which other arguments.
+ */
+
+wizard(ron).
+hasWand(harry).
+quidditchPlayer(harry).
+wizard(X):-  hasBroom(X),  hasWand(X).
+hasBroom(X):-  quidditchPlayer(X).
+
+/**
+ * a. ii.
+ * 1. wizard(ron). This returns true, since ron is defined as a wizard; but if a semicolon
+ * is pressed, it returns false, since hasBroom(ron). and hasWand(ron). are not stated.
+ * 2. witch(ron). This returns ERROR: Undefined procedure: witch/1 (DWIM could not correct
+ * goal), since the functor witch is not defined.
+ * 3. wizard(hermione). This returns false, because wizard(hermione). is not stated, and 
+ * neither are hasBroom(hermione). and hasWand(hermione).
+ * 4. witch(hermione). This returns ERROR: Undefined procedure: witch/1 (DWIM could not
+ * correct goal), since the functor witch is not defined.
+ * 5. wizard(harry). This returns true; while wizard(harry). is not expressly stated,
+ * hasBroom(harry). and hasWand(harry). are, which through modus ponens Prolog can use
+ * to conclude wizard(harry).
+ * 6. wizard(Y). This returns Y = ron, and if a semicolon is typed it returns Y = harry.
+ * Y = ron is returned because wizard(ron). is expressly stated, and Y = harry is returned
+ * for the same reason wizard(harry). returned true in the previous query.
+ * 7. witch(Y). This returns ERROR: Undefined procedure: witch/1 (DWIM could not
+ * correct goal), since the functor witch is not defined.
+ */

lab12/lab_2.pl

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+/**
+ * a. i.
+ * 1. bread  =  bread -> true. No instantiation occurs because there are no
+ * variables involved.
+ * 2. ’Bread’  =  bread -> false. No instantiation occurs because there are
+ * no variables involved.
+ * 8. food(X)  =  food(bread) -> X = bread. X is instantiated to bread.
+ * 9. food(bread,X)  =  food(Y,sausage) -> X = sausage, Y = bread. X is 
+ * instantiated to sausage, Y is instantiated to bread.
+ * 14. meal(food(bread),X)  =  meal(X,drink(beer)) -> false. If X is
+ * instantiated to drink(beer) then 
+ * meal(food(bread),drink(beer)) != meal(drink(beer),drink(beer)). If X is 
+ * instantiated to food(bread), then
+ * meal(food(bread),food(bread)) != meal(food(bread),drink(beer)).
+ */
+
+wizard(tom).
+house_elf(dobby).
+witch(hermione).
+witch('McGonagall').
+witch(rita_skeeter).
+magic(X):-house_elf(X).
+magic(X):-wizard(X).
+magic(X):-witch(X).
+
+/* Swi-prolog doesn't allow us to query using functors that haven't been previously defined. In short, 
+it doesn't allow us to unify variables with functors that haven't been used before.
+For instance:
+magic(house_elf).
+wizard(harry).
+magic(wizard).
+all return me variations on this error: Undefined procedure: wizard/1.....
+wizard/1 has not been used, so it cannot be queried (wizard(harry). and magic(wizard).) and it additionally
+prevents magic/1 being used on other functors, since magic/1 depends on wizard/1
+However, if I add to the knowledge base the line
+wizard(tom).
+(or any other random atomic that has no relevance to the rest of the knowledge base, not necessarily tom)
+then all three return actual values (false, in each case), because the functor has now been defined and used.
+ */

lab12/lab_3.pl

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+weighsduck(lady).
+floats(X):-weighsduck(X).
+wood(X):-floats(X).
+burn(X):-wood(X).
+witch(X):-burn(X).
+
+/* witch(lady). returns true */