There is a better than even chance that Sandra left the apple. We doubt that Greg is a rhino. Chances are about even that Lily is green. There is a better than even chance that if either 'Lily is green' or 'Sandra left the apple' but not both then John moved to the office. Chances are slight that if either 'Greg is a rhino' or 'Sandra left the apple' but not both then Mary went to the garden. It is highly unlikely that if 'Sandra left the apple and Greg is a rhino' then Bernhard is a frog.
It is impossible that 'Mary went to the garden' or 'Lily is green' or both.
Chances are about even that 'Mary went to the garden' or 'Lily is green' or both.
It is impossible that 'Mary went to the garden' or 'Lily is green' 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
  0.6::factA.
  0.2::factB.
  0.5::factC.
  %hop1
  0.6::factX:-xor(factC,factA).
  0.1::factY:-xor(factB,factA).
  0.05::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Mary went to the garden' or 'Lily is green' or both.