It is highly unlikely that Bill got the milk there. It is improbable that John went to the office. It is certain that Mary left the apple. We believe that if 'John went to the office and Mary left the apple' then Winona is a wolf. It is highly unlikely that if 'Bill got the milk there and John went to the office' then Brian is yellow. It is almost certain that if 'John went to the office' or 'Mary left the apple' or both then Bernhard is a swan.
There is almost no chance that 'Bill got the milk there' or 'Mary left the apple' or both.
It is certain that 'Bill got the milk there' or 'Mary left the apple' or both.
There is almost no chance that 'Bill got the milk there' or 'Mary left the apple' 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
  0.05::factA.
  0.1::factB.
  1.0::factC.
  %hop1
  0.75::factX:-and(factB,factC).
  0.05::factY:-and(factA,factB).
  0.95::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Bill got the milk there' or 'Mary left the apple' or both.