It is highly unlikely that Bernhard is yellow. There is almost no chance that Winona is a sheep. There is little chance that John discarded the apple. It is likely that if 'Bernhard is yellow' or 'Winona is a sheep' or both then Jeff left the football. There is a very good chance that if 'Bernhard is yellow' or 'John discarded the apple' or both then Brian is a frog. There is almost no chance that if 'Bernhard is yellow' or 'Winona is a sheep' or both then Mary got the football.
It is highly unlikely that either 'Winona is a sheep' or 'Bernhard is yellow' but not both.
It is highly unlikely that either 'Winona is a sheep' or 'Bernhard is yellow' but not both.
It is likely that either 'Winona is a sheep' or 'Bernhard is yellow' 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
  0.05::factA.
  0.02::factB.
  0.1::factC.
  %hop1
  0.7::factX:-or(factA,factB).
  0.8::factY:-or(factA,factC).
  0.02::factZ:-or(factA,factB).

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

  query(conclusion).
  
Either 'Winona is a sheep' or 'Bernhard is yellow' but not both.