It is probably the case that Julius is a rhino. Chances are slight that Sandra took the milk. We believe that Mary went to the office. It is likely that if 'Mary went to the office and Julius is a rhino' then Lily is gray. It is certain that if either 'Sandra took the milk' or 'Mary went to the office' but not both then Greg is a frog. It is likely that if 'Julius is a rhino' or 'Sandra took the milk' or both then John got the football.
It is improbable that 'Greg is a frog' or 'Lily is gray' or both.
We believe that 'Greg is a frog' or 'Lily is gray' or both.
It is improbable that 'Greg is a frog' or 'Lily 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
  0.7::factA.
  0.1::factB.
  0.75::factC.
  %hop1
  0.7::factX:-and(factC,factA).
  1.0::factY:-xor(factB,factC).
  0.7::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Greg is a frog' or 'Lily is gray' or both.