It is certain that Brian is a frog. It is probably not the case that Jason is tired. Chances are slight that John took the football. It is highly unlikely that if 'Brian is a frog' or 'John took the football' or both then Sumit is thirsty. There is a very good chance that if either 'Jason is tired' or 'John took the football' but not both then Bernhard is yellow. It is certain that if either 'Brian is a frog' or 'John took the football' but not both then Mary went to the hallway.
It is improbable that either 'Mary went to the hallway' or 'Bernhard is yellow' but not both.
There is a very good chance that either 'Mary went to the hallway' or 'Bernhard is yellow' but not both.
It is improbable that either 'Mary went to the hallway' 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
  1.0::factA.
  0.25::factB.
  0.1::factC.
  %hop1
  0.05::factX:-or(factA,factC).
  0.8::factY:-xor(factB,factC).
  1.0::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Mary went to the hallway' or 'Bernhard is yellow' but not both.