It is likely that Bernhard is a frog. It is probable that Greg is a lion. It is likely that Sumit is bored. Chances are about even that if 'Greg is a lion' or 'Bernhard is a frog' or both then Winona is a mouse. There is a better than even chance that if either 'Greg is a lion' or 'Bernhard is a frog' but not both then Daniel took the apple. It is highly likely that if 'Sumit is bored and Bernhard is a frog' then Brian is a swan.
It is impossible that either 'Bernhard is a frog' or 'Greg is a lion' but not both.
Chances are about even that either 'Bernhard is a frog' or 'Greg is a lion' but not both.
It is impossible that either 'Bernhard is a frog' 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
  0.7::factA.
  0.7::factB.
  0.7::factC.
  %hop1
  0.5::factX:-or(factB,factA).
  0.6::factY:-xor(factB,factA).
  0.9::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'Bernhard is a frog' or 'Greg is a lion' but not both.