It is likely that Mary took the football. It is certain that John put down the apple. There is a very good chance that Lily is yellow. There is little chance that if 'Mary took the football' or 'John put down the apple' or both then Gertrude is a mouse. It is impossible that if either 'John put down the apple' or 'Mary took the football' but not both then Julius is a lion. There is a better than even chance that if 'Lily is yellow' or 'Mary took the football' or both then Bernhard is a frog.
There is little chance that 'Bernhard is a frog' or 'Julius is a lion' or both.
There is a better than even chance that 'Bernhard is a frog' or 'Julius is a lion' or both.
There is little chance that 'Bernhard is a frog' or 'Julius is a lion' 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.
  1.0::factB.
  0.8::factC.
  %hop1
  0.1::factX:-or(factA,factB).
  0.0::factY:-xor(factB,factA).
  0.6::factZ:-or(factC,factA).

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

  query(conclusion).
  
'Bernhard is a frog' or 'Julius is a lion' or both.