Examples of Facts
- female(alison).
- “alison is a female”
- has_feathers(sparrow).
- “sparrow has feathers”
- father(“John”,”Sam”).
- ”John is the father to Sam”
- mother(”Jeanette”,”Mary”).
- “Jeanette is the mother to Mary”
- bird(type(sparrow), name(toto))).
- “toto is a bird that is of sparrow class”
Examples of Rules
- You should read the prolog operator “:-” as “if ”, “;” as an “or”, while “,” as meaning “and”.
- Rules consist of a head and a body. For example the rule “a(X) :- b(X), c(X).” has head “a(X)” and body “b(X), c(X)”.
- All arguments beginning with a capital letter (such as X and Y) are variables. Variables don't have to have values). Any constant should NOT begin with a capital letter else it will be treated as a variable.
- sister(X,Y) :- father(Z,X),father(Z,Y).
- “X and Y are sisters if Z is father to X and father to Y”
Example of a Prolog Program
PREDICATES
son(STRING, STRING)
CLAUSES
son("John", "Dan").
son("Allan","Dan").
Goal son("John", "Dan").
Example 2
PREDICATES
son(STRING,STRING)
sister(STRING,STRING)
brother(STRING,STRING)
married(STRING,STRING)
sister_in_law(STRING,STRING)
CLAUSES
son("John", "Dan").
sister("Mary","Suzan").
brother("Harold", "Larry").
married("John", "Mary").
married("Larry", "Sue").
married("Harold", "Emma").
CLAUSES
sister_in_law(A, B):-married(A, C), sister(C, B).
sister_in_law(A, B):-brother(A, C), married(C, B).
GOAL
sister_in_law("John", Z).
Example 3
domains
brand, color = symbol
age, price = integer
milage = real
predicates
car(brand, milage, age, color, price)
clauses
car(chrysler, 130000, 3, red, 12000).
car(ford, 90000, 4, gray, 25000).
car(datsun, 8000, 1, red, 30000).
goal
car(renault, 13, 3.5, red, 12000).
/* car(ford, 9000, gray, 4, 25000).
car(Make, Odometer, Years_on_road, Body, 25000).
car(Make, Odometer, Years_on_road, Body, Cost) and Cost < style=""> */
