It is probable that Brian is yellow. There is a very good chance that Bernhard is yellow. There is a better than even chance that Greg is a swan. Chances are about even that if 'Bernhard is yellow and Greg is a swan' then Emily is a mouse. There is almost no chance that if either 'Brian is yellow' or 'Greg is a swan' but not both then Mary went to the office. It is probably the case that if 'Brian is yellow' or 'Bernhard is yellow' or both then Julius is a lion.
It is unlikely that either 'Mary went to the office' or 'Julius is a lion' but not both.
It is probably the case that either 'Mary went to the office' or 'Julius is a lion' but not both.
It is unlikely that either 'Mary went to the office' or 'Julius is a lion' 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.
  0.8::factB.
  0.6::factC.
  %hop1
  0.5::factX:-and(factB,factC).
  0.02::factY:-xor(factA,factC).
  0.7::factZ:-or(factA,factB).

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

  query(conclusion).
  
Either 'Mary went to the office' or 'Julius is a lion' but not both.