It is probably not the case that Greg is green. There is almost no chance that Julius is yellow. It is probably not the case that Mary took the football. It is probable that if 'Julius is yellow and Mary took the football' then Bernhard is a swan. It is improbable that if 'Mary took the football and Greg is green' then Brian is white. There is almost no chance that if 'Mary took the football and Greg is green' then John went to the office.
It is probably not the case that either 'John went to the office' or 'Greg is green' but not both.
It is probably not the case that either 'John went to the office' or 'Greg is green' but not both.
It is highly likely that either 'John went to the office' or 'Greg is green' but not 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
  0.25::factA.
  0.02::factB.
  0.25::factC.
  %hop1
  0.7::factX:-and(factB,factC).
  0.1::factY:-and(factC,factA).
  0.02::factZ:-and(factC,factA).

  %hop2
  conclusion:-xor(factZ,factA).

  query(conclusion).
  
Either 'John went to the office' or 'Greg is green' but not both.