It is probable that Mary moved to the office. We doubt that John took the apple. Chances are slight that Winona is a sheep. It is improbable that if 'John took the apple' or 'Winona is a sheep' or both then Greg is a frog. We doubt that if either 'Mary moved to the office' or 'John took the apple' but not both then Lily is yellow. It is almost certain that if 'Winona is a sheep and John took the apple' then Brian is a swan.
It is certain that 'Greg is a frog' or 'Winona is a sheep' or both.
There is little chance that 'Greg is a frog' or 'Winona is a sheep' or both.
It is certain that 'Greg is a frog' or 'Winona is a sheep' 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.
  0.2::factB.
  0.1::factC.
  %hop1
  0.1::factX:-or(factB,factC).
  0.2::factY:-xor(factA,factB).
  0.95::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Greg is a frog' or 'Winona is a sheep' or both.