We doubt that Greg is a lion. Chances are about even that Bernhard is yellow. It is highly unlikely that Mary grabbed the apple. It is highly unlikely that if 'Greg is a lion and Mary grabbed the apple' then John got the milk. It is almost certain that if 'Mary grabbed the apple' or 'Greg is a lion' or both then Brian is a swan. We doubt that if either 'Greg is a lion' or 'Bernhard is yellow' but not both then Jessica is a mouse.
It is probable that 'Mary grabbed the apple' or 'Greg is a lion' or both.
It is probably not the case that 'Mary grabbed the apple' or 'Greg is a lion' or both.
It is probable that 'Mary grabbed the apple' or 'Greg is a lion' 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.
  0.5::factB.
  0.05::factC.
  %hop1
  0.05::factX:-and(factA,factC).
  0.95::factY:-or(factC,factA).
  0.2::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'Mary grabbed the apple' or 'Greg is a lion' or both.