Chances are about even that Fred is in the cinema. It is highly unlikely that Julius is yellow. Chances are slight that Mary got the football. We believe that if either 'Julius is yellow' or 'Mary got the football' but not both then Greg is a rhino. It is likely that if 'Julius is yellow and Fred is in the cinema' then John went to the garden. There is a better than even chance that if 'Mary got the football' or 'Julius is yellow' or both then Bernhard is a swan.
There is a very good chance that 'Bernhard is a swan' or 'Julius is yellow' or both.
There is little chance that 'Bernhard is a swan' or 'Julius is yellow' or both.
There is a very good chance that 'Bernhard is a swan' or 'Julius is yellow' 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
  0.5::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.75::factX:-xor(factB,factC).
  0.7::factY:-and(factB,factA).
  0.6::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Bernhard is a swan' or 'Julius is yellow' or both.