It is likely that Brian is white. It is certain that Daniel grabbed the milk. It is probable that Winona is a mouse. Chances are about even that if 'Winona is a mouse and Daniel grabbed the milk' then Julius is yellow. It is highly likely that if 'Daniel grabbed the milk and Winona is a mouse' then Mary left the football. There is almost no chance that if 'Brian is white' or 'Winona is a mouse' or both then Greg is a rhino.
There is a better than even chance that 'Greg is a rhino' or 'Mary left the football' or both.
There is a better than even chance that 'Greg is a rhino' or 'Mary left the football' or both.
It is impossible that 'Greg is a rhino' or 'Mary left the football' 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
  0.7::factA.
  1.0::factB.
  0.7::factC.
  %hop1
  0.5::factX:-and(factC,factB).
  0.9::factY:-and(factB,factC).
  0.02::factZ:-or(factA,factC).

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

  query(conclusion).
  
'Greg is a rhino' or 'Mary left the football' or both.