It is impossible that Jeff went to the garden. It is probably the case that Fred left the football. Chances are about even that Julius is white. We believe that if 'Jeff went to the garden and Fred left the football' then Mary dropped the milk. It is probable that if 'Jeff went to the garden' or 'Julius is white' or both then Bernhard is a rhino. There is almost no chance that if either 'Fred left the football' or 'Julius is white' but not both then Brian is a frog.
Chances are about even that 'Julius is white' or 'Brian is a frog' or both.
Chances are about even that 'Julius is white' or 'Brian is a frog' or both.
It is highly unlikely that 'Julius is white' or 'Brian is a frog' 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
  0.0::factA.
  0.7::factB.
  0.5::factC.
  %hop1
  0.75::factX:-and(factA,factB).
  0.7::factY:-or(factA,factC).
  0.02::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Julius is white' or 'Brian is a frog' or both.