We doubt that Julius is a swan. It is probably not the case that Lily is green. It is highly likely that Greg is a rhino. We believe that if either 'Lily is green' or 'Greg is a rhino' but not both then Bill went to the bedroom. It is highly likely that if either 'Lily is green' or 'Greg is a rhino' but not both then Brian is white. It is likely that if either 'Lily is green' or 'Greg is a rhino' but not both then Mary left the milk.
It is highly likely that 'Greg is a rhino' or 'Bill went to the bedroom' or both.
It is highly likely that 'Greg is a rhino' or 'Bill went to the bedroom' or both.
It is impossible that 'Greg is a rhino' or 'Bill went to the bedroom' 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
  0.2::factA.
  0.25::factB.
  0.9::factC.
  %hop1
  0.75::factX:-xor(factB,factC).
  0.9::factY:-xor(factB,factC).
  0.7::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Greg is a rhino' or 'Bill went to the bedroom' or both.