Chances are slight that Greg is white. There is a very good chance that Fred went to the garden. It is unlikely that Brian is a frog. Chances are about even that if 'Greg is white' or 'Fred went to the garden' or both then Bernhard is a lion. There is a better than even chance that if either 'Greg is white' or 'Fred went to the garden' but not both then Gertrude is a cat. There is almost no chance that if 'Fred went to the garden' or 'Brian is a frog' or both then Mary left the milk.
There is little chance that 'Bernhard is a lion and Brian is a frog'.
There is little chance that 'Bernhard is a lion and Brian is a frog'.
There is a better than even chance that 'Bernhard is a lion and Brian is a frog'.

  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.
  0.8::factB.
  0.2::factC.
  %hop1
  0.5::factX:-or(factA,factB).
  0.6::factY:-xor(factA,factB).
  0.02::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Bernhard is a lion and Brian is a frog'.