There is a better than even chance that Mary left the milk. There is little chance that Brian is white. Chances are slight that Sandra dropped the apple. It is highly unlikely that if 'Sandra dropped the apple and Mary left the milk' then Greg is a frog. It is almost certain that if 'Sandra dropped the apple' or 'Brian is white' or both then Emily is a wolf. Chances are about even that if 'Mary left the milk and Sandra dropped the apple' then Lily is green.
It is likely that 'Brian is white' or 'Greg is a frog' or both.
It is improbable that 'Brian is white' or 'Greg is a frog' or both.
It is likely that 'Brian is white' or 'Greg is a frog' 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.
  0.1::factB.
  0.1::factC.
  %hop1
  0.05::factX:-and(factC,factA).
  0.95::factY:-or(factC,factB).
  0.5::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Brian is white' or 'Greg is a frog' or both.