It is probably not the case that John got the milk. We doubt that Greg is a lion. It is likely that Winona is a mouse. Chances are about even that if 'Winona is a mouse' or 'Greg is a lion' or both then Mary went to the kitchen. We believe that if 'Winona is a mouse' or 'John got the milk' or both then Jessica is a sheep. There is almost no chance that if either 'Greg is a lion' or 'John got the milk' but not both then Fred moved to the office.
It is unlikely that 'Greg is a lion' or 'Fred moved to the office' or both.
It is unlikely that 'Greg is a lion' or 'Fred moved to the office' or both.
It is likely that 'Greg is a lion' or 'Fred moved to the office' 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
  0.25::factA.
  0.2::factB.
  0.7::factC.
  %hop1
  0.5::factX:-or(factC,factB).
  0.75::factY:-or(factC,factA).
  0.02::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Greg is a lion' or 'Fred moved to the office' or both.