It is certain that Lily is a swan. There is a very good chance that Gertrude is a mouse. There is almost no chance that Greg is a frog. It is probably the case that if either 'Greg is a frog' or 'Gertrude is a mouse' but not both then Sandra put down the milk. It is likely that if 'Gertrude is a mouse and Greg is a frog' then Brian is white. It is certain that if either 'Gertrude is a mouse' or 'Lily is a swan' but not both then John went to the kitchen.
Chances are slight that 'Gertrude is a mouse' or 'John went to the kitchen' or both.
It is certain that 'Gertrude is a mouse' or 'John went to the kitchen' or both.
Chances are slight that 'Gertrude is a mouse' or 'John went to the kitchen' 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
  1.0::factA.
  0.8::factB.
  0.02::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.7::factY:-and(factB,factC).
  1.0::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Gertrude is a mouse' or 'John went to the kitchen' or both.