We believe that Jason is tired. There is a better than even chance that Greg is a frog. It is probably not the case that Fred discarded the apple. Chances are about even that if 'Fred discarded the apple and Jason is tired' then John left the milk. It is impossible that if 'Greg is a frog and Jason is tired' then Brian is a rhino. There is little chance that if either 'Fred discarded the apple' or 'Greg is a frog' but not both then Julius is white.
It is impossible that 'John left the milk and Julius is white'.
It is impossible that 'John left the milk and Julius is white'.
We believe that 'John left the milk and Julius is white'.

  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
  0.75::factA.
  0.6::factB.
  0.25::factC.
  %hop1
  0.5::factX:-and(factC,factA).
  0.0::factY:-and(factB,factA).
  0.1::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'John left the milk and Julius is white'.