It is likely that Bernhard is gray. It is probable that Fred went to the garden. It is probable that John discarded the apple. Chances are about even that if 'Bernhard is gray' or 'Fred went to the garden' or both then Julius is white. It is almost certain that if 'John discarded the apple' or 'Bernhard is gray' or both then Brian is green. It is improbable that if 'Fred went to the garden and John discarded the apple' then Greg is a frog.
There is little chance that 'Brian is green' or 'Julius is white' or both.
It is highly likely that 'Brian is green' or 'Julius is white' or both.
There is little chance that 'Brian is green' or 'Julius is white' 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.
  0.7::factB.
  0.7::factC.
  %hop1
  0.5::factX:-or(factA,factB).
  0.95::factY:-or(factC,factA).
  0.1::factZ:-and(factB,factC).

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

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