It is probable that Bernhard is a rhino. It is impossible that Mary got the football. It is probable that Greg is a lion. It is likely that if 'Greg is a lion and Mary got the football' then John went to the office. It is highly likely that if 'Bernhard is a rhino and Greg is a lion' then Brian is yellow. Chances are about even that if 'Greg is a lion' or 'Bernhard is a rhino' or both then Julius is yellow.
It is likely that either 'John went to the office' or 'Bernhard is a rhino' but not both.
It is likely that either 'John went to the office' or 'Bernhard is a rhino' but not both.
It is impossible that either 'John went to the office' or 'Bernhard is a rhino' 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
  0.7::factA.
  0.0::factB.
  0.7::factC.
  %hop1
  0.7::factX:-and(factC,factB).
  0.9::factY:-and(factA,factC).
  0.5::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'John went to the office' or 'Bernhard is a rhino' but not both.