It is impossible that Julius is gray. It is probably the case that Greg is a frog. It is likely that Brian is white. Chances are about even that if 'Julius is gray' or 'Greg is a frog' or both then Winona is a cat. There is a very good chance that if 'Julius is gray and Brian is white' then John discarded the milk. It is unlikely that if either 'Brian is white' or 'Julius is gray' but not both then Jason is tired.
It is likely that 'Brian is white' or 'Jason is tired' or both.
It is likely that 'Brian is white' or 'Jason is tired' or both.
There is almost no chance that 'Brian is white' or 'Jason is tired' 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.
  0.7::factC.
  %hop1
  0.5::factX:-or(factA,factB).
  0.8::factY:-and(factA,factC).
  0.2::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Brian is white' or 'Jason is tired' or both.