We doubt that Greg is white. It is almost certain that Gertrude is a sheep. There is almost no chance that John went to the hallway. It is unlikely that if 'Greg is white' or 'John went to the hallway' or both then Lily is a rhino. It is probably not the case that if 'Greg is white' or 'John went to the hallway' or both then Julius is white. It is probable that if either 'Gertrude is a sheep' or 'John went to the hallway' but not both then Sandra dropped the milk.
We believe that 'Lily is a rhino and Gertrude is a sheep'.
It is highly unlikely that 'Lily is a rhino and Gertrude is a sheep'.
We believe that 'Lily is a rhino and Gertrude is a sheep'.

  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.
  0.95::factB.
  0.02::factC.
  %hop1
  0.2::factX:-or(factA,factC).
  0.25::factY:-or(factA,factC).
  0.7::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Lily is a rhino and Gertrude is a sheep'.