It is improbable that Brian is a frog. It is improbable that Lily is white. It is unlikely that John dropped the apple. It is probably the case that if 'John dropped the apple' or 'Brian is a frog' or both then Greg is a swan. There is a very good chance that if 'Brian is a frog' or 'Lily is white' or both then Mary went to the bedroom. It is certain that if either 'Lily is white' or 'Brian is a frog' but not both then Julius is a lion.
It is unlikely that 'Brian is a frog' or 'Mary went to the bedroom' or both.
It is unlikely that 'Brian is a frog' or 'Mary went to the bedroom' or both.
It is probable that 'Brian is a frog' or 'Mary went to the bedroom' 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
  0.1::factA.
  0.1::factB.
  0.2::factC.
  %hop1
  0.7::factX:-or(factC,factA).
  0.8::factY:-or(factA,factB).
  1.0::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Brian is a frog' or 'Mary went to the bedroom' or both.