It is probably not the case that Bill went to the office. We doubt that Emily is a cat. It is probably the case that Lily is a rhino. We believe that if 'Emily is a cat and Lily is a rhino' then Greg is a lion. There is a very good chance that if either 'Bill went to the office' or 'Emily is a cat' but not both then Brian is yellow. It is highly likely that if 'Bill went to the office and Lily is a rhino' then John dropped the milk.
It is probably not the case that either 'Brian is yellow' or 'Greg is a lion' but not both.
It is probably not the case that either 'Brian is yellow' or 'Greg is a lion' but not both.
It is probable that either 'Brian is yellow' or 'Greg 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
  0.25::factA.
  0.2::factB.
  0.7::factC.
  %hop1
  0.75::factX:-and(factB,factC).
  0.8::factY:-xor(factA,factB).
  0.9::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Brian is yellow' or 'Greg is a lion' but not both.