We believe that Brian is white. Chances are slight that Jessica is a sheep. There is little chance that Mary left the apple. Chances are about even that if either 'Jessica is a sheep' or 'Mary left the apple' but not both then Julius is a swan. Chances are slight that if 'Mary left the apple and Jessica is a sheep' then Bernhard is yellow. It is improbable that if 'Brian is white and Mary left the apple' then Sandra got the football.
We believe that 'Brian is white' or 'Julius is a swan' or both.
We believe that 'Brian is white' or 'Julius is a swan' or both.
It is probably not the case that 'Brian is white' or 'Julius is a swan' 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
  0.75::factA.
  0.1::factB.
  0.1::factC.
  %hop1
  0.5::factX:-xor(factB,factC).
  0.1::factY:-and(factC,factB).
  0.1::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Brian is white' or 'Julius is a swan' or both.