It is probably the case that Brian is gray. There is a very good chance that Gertrude is a sheep. Chances are about even that Daniel left the apple. It is almost certain that if either 'Daniel left the apple' or 'Gertrude is a sheep' but not both then Jeff went to the bedroom. Chances are about even that if 'Brian is gray' or 'Daniel left the apple' or both then Julius is a rhino. We believe that if either 'Gertrude is a sheep' or 'Brian is gray' but not both then Greg is gray.
It is highly unlikely that either 'Gertrude is a sheep' or 'Brian is gray' but not both.
Chances are about even that either 'Gertrude is a sheep' or 'Brian is gray' but not both.
It is highly unlikely that either 'Gertrude is a sheep' or 'Brian is gray' 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.
  0.5::factC.
  %hop1
  0.95::factX:-xor(factC,factB).
  0.5::factY:-or(factA,factC).
  0.75::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Gertrude is a sheep' or 'Brian is gray' but not both.