It is probable that Brian is a frog. It is impossible that Mary picked up the milk. There is a very good chance that Greg is a rhino. We doubt that if either 'Mary picked up the milk' or 'Greg is a rhino' but not both then Julius is yellow. It is probably the case that if 'Greg is a rhino' or 'Brian is a frog' or both then Jason is tired. Chances are slight that if 'Mary picked up the milk' or 'Brian is a frog' or both then Lily is a swan.
It is unlikely that 'Brian is a frog' or 'Julius is yellow' or both.
We believe that 'Brian is a frog' or 'Julius is yellow' or both.
It is unlikely that 'Brian is a frog' or 'Julius is yellow' 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.
  0.0::factB.
  0.8::factC.
  %hop1
  0.2::factX:-xor(factB,factC).
  0.7::factY:-or(factC,factA).
  0.1::factZ:-or(factB,factA).

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

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