It is probable that Julius is a lion. It is certain that Gertrude is a cat. It is probable that Mary went to the kitchen. It is probably not the case that if either 'Mary went to the kitchen' or 'Gertrude is a cat' but not both then Brian is yellow. Chances are slight that if either 'Gertrude is a cat' or 'Mary went to the kitchen' but not both then John left the football. It is almost certain that if 'Mary went to the kitchen and Julius is a lion' then Greg is a swan.
It is unlikely that 'Brian is yellow' or 'Gertrude is a cat' or both.
It is certain that 'Brian is yellow' or 'Gertrude is a cat' or both.
It is unlikely that 'Brian is yellow' or 'Gertrude is a cat' or 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
  0.7::factA.
  1.0::factB.
  0.7::factC.
  %hop1
  0.25::factX:-xor(factC,factB).
  0.1::factY:-xor(factB,factC).
  0.95::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Brian is yellow' or 'Gertrude is a cat' or both.