Chances are about even that Mary got the football. It is impossible that Greg is a swan. It is highly likely that Brian is white. It is probably the case that if 'Greg is a swan' or 'Mary got the football' or both then John discarded the apple. It is highly likely that if 'Brian is white and Mary got the football' then Jeff went to the garden. It is impossible that if 'Mary got the football' or 'Greg is a swan' or both then Julius is yellow.
It is probably not the case that 'Julius is yellow' or 'John discarded the apple' or both.
It is probably not the case that 'Julius is yellow' or 'John discarded the apple' or both.
It is certain that 'Julius is yellow' or 'John discarded the apple' 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
  0.5::factA.
  0.0::factB.
  0.9::factC.
  %hop1
  0.7::factX:-or(factB,factA).
  0.9::factY:-and(factC,factA).
  0.0::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Julius is yellow' or 'John discarded the apple' or both.