We doubt that Lily is a rhino. It is improbable that Greg is gray. It is impossible that John went to the office. It is unlikely that if either 'Greg is gray' or 'Lily is a rhino' but not both then Mary left the football. There is little chance that if 'Lily is a rhino' or 'John went to the office' or both then Winona is a sheep. It is highly likely that if 'John went to the office and Greg is gray' then Brian is a frog.
There is a better than even chance that 'Brian is a frog' or 'Mary left the football' or both.
It is highly unlikely that 'Brian is a frog' or 'Mary left the football' or both.
There is a better than even chance that 'Brian is a frog' or 'Mary left the football' 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.
  0.1::factB.
  0.0::factC.
  %hop1
  0.2::factX:-xor(factB,factA).
  0.1::factY:-or(factA,factC).
  0.9::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Brian is a frog' or 'Mary left the football' or both.