It is certain that Mary went to the bedroom. It is probable that Bernhard is white. There is a better than even chance that Jason is bored. It is highly unlikely that if 'Mary went to the bedroom and Bernhard is white' then Brian is a frog. It is improbable that if 'Jason is bored' or 'Bernhard is white' or both then Lily is a lion. Chances are slight that if 'Mary went to the bedroom and Jason is bored' then Winona is a mouse.
It is likely that either 'Bernhard is white' or 'Brian is a frog' but not both.
It is likely that either 'Bernhard is white' or 'Brian is a frog' but not both.
Chances are slight that either 'Bernhard is white' or 'Brian is a frog' but not both.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  1.0::factA.
  0.7::factB.
  0.6::factC.
  %hop1
  0.05::factX:-and(factA,factB).
  0.1::factY:-or(factC,factB).
  0.1::factZ:-and(factA,factC).

  %hop2
  conclusion:-xor(factB,factX).

  query(conclusion).
  
Either 'Bernhard is white' or 'Brian is a frog' but not both.