There is a better than even chance that Greg is yellow. It is probable that Gertrude is a mouse. It is highly unlikely that Julius is gray. There is almost no chance that if 'Julius is gray and Greg is yellow' then Sandra took the football. It is improbable that if 'Julius is gray and Gertrude is a mouse' then Brian is a swan. There is almost no chance that if 'Gertrude is a mouse and Greg is yellow' then John went to the kitchen.
It is highly unlikely that 'Julius is gray' or 'Brian is a swan' or both.
It is highly unlikely that 'Julius is gray' or 'Brian is a swan' or both.
It is probably the case that 'Julius is gray' or 'Brian is a swan' 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
  0.6::factA.
  0.7::factB.
  0.05::factC.
  %hop1
  0.02::factX:-and(factC,factA).
  0.1::factY:-and(factC,factB).
  0.02::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Julius is gray' or 'Brian is a swan' or both.