It is probable that Brian is a lion. It is highly likely that Gertrude is a wolf. There is almost no chance that Bernhard is a frog. There is a very good chance that if 'Brian is a lion and Bernhard is a frog' then Lily is green. It is probable that if 'Gertrude is a wolf' or 'Brian is a lion' or both then Mary left the football. It is probably the case that if 'Bernhard is a frog' or 'Brian is a lion' or both then Greg is a swan.
It is impossible that either 'Bernhard is a frog' or 'Gertrude is a wolf' but not both.
It is highly likely that either 'Bernhard is a frog' or 'Gertrude is a wolf' but not both.
It is impossible that either 'Bernhard is a frog' or 'Gertrude is a wolf' 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.
  0.9::factB.
  0.02::factC.
  %hop1
  0.8::factX:-and(factA,factC).
  0.7::factY:-or(factB,factA).
  0.7::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Bernhard is a frog' or 'Gertrude is a wolf' but not both.