It is probably the case that Gertrude is a sheep. Chances are about even that Greg is a swan. We believe that Mary moved to the office. It is unlikely that if either 'Gertrude is a sheep' or 'Mary moved to the office' but not both then Lily is green. It is almost certain that if 'Mary moved to the office' or 'Greg is a swan' or both then Bernhard is green. There is little chance that if 'Gertrude is a sheep' or 'Mary moved to the office' or both then Julius is yellow.
It is highly unlikely that 'Julius is yellow and Greg is a swan'.
It is highly unlikely that 'Julius is yellow and Greg is a swan'.
It is highly likely that 'Julius is yellow and Greg is a swan'.

  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.
  0.5::factB.
  0.75::factC.
  %hop1
  0.2::factX:-xor(factA,factC).
  0.95::factY:-or(factC,factB).
  0.1::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Julius is yellow and Greg is a swan'.