We believe that John put down the milk. It is improbable that Sandra dropped the apple. It is impossible that Julius is gray. Chances are about even that if either 'Julius is gray' or 'Sandra dropped the apple' but not both then Mary moved to the office. There is little chance that if 'John put down the milk' or 'Julius is gray' or both then Greg is white. It is probably the case that if 'John put down the milk and Julius is gray' then Bernhard is yellow.
Chances are about even that 'Mary moved to the office' or 'Julius is gray' or both.
It is highly unlikely that 'Mary moved to the office' or 'Julius is gray' or both.
Chances are about even that 'Mary moved to the office' or 'Julius is gray' 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
  0.75::factA.
  0.1::factB.
  0.0::factC.
  %hop1
  0.5::factX:-xor(factC,factB).
  0.1::factY:-or(factA,factC).
  0.7::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Mary moved to the office' or 'Julius is gray' or both.