It is improbable that Julius is a swan. There is a better than even chance that Gertrude is a cat. It is unlikely that Bernhard is gray. We doubt that if 'Bernhard is gray' or 'Gertrude is a cat' or both then Greg is yellow. There is little chance that if 'Julius is a swan' or 'Bernhard is gray' or both then Mary went to the office. It is likely that if 'Julius is a swan and Gertrude is a cat' then Winona is a sheep.
It is likely that 'Gertrude is a cat' or 'Bernhard is gray' or both.
It is likely that 'Gertrude is a cat' or 'Bernhard is gray' or both.
There is little chance that 'Gertrude is a cat' or 'Bernhard is gray' 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
  0.1::factA.
  0.6::factB.
  0.2::factC.
  %hop1
  0.2::factX:-or(factC,factB).
  0.1::factY:-or(factA,factC).
  0.7::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Gertrude is a cat' or 'Bernhard is gray' or both.