We doubt that Mary got the apple. It is likely that Greg is yellow. It is likely that John left the milk. There is a better than even chance that if 'John left the milk and Mary got the apple' then Jessica is a mouse. We doubt that if 'Mary got the apple and John left the milk' then Julius is white. It is unlikely that if 'Greg is yellow' or 'John left the milk' or both then Brian is green.
It is unlikely that 'Jessica is a mouse' or 'Greg is yellow' or both.
We believe that 'Jessica is a mouse' or 'Greg is yellow' or both.
It is unlikely that 'Jessica is a mouse' or 'Greg is yellow' 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.
  0.7::factB.
  0.7::factC.
  %hop1
  0.6::factX:-and(factC,factA).
  0.2::factY:-and(factA,factC).
  0.2::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Jessica is a mouse' or 'Greg is yellow' or both.