context: It is certain that Bernhard is a rhino. It is improbable that Jason is bored. It is improbable that John picked up the milk. There is a very good chance that if 'John picked up the milk and Bernhard is a rhino' then Julius is a swan. There is almost no chance that if either 'Bernhard is a rhino' or 'John picked up the milk' but not both then Brian is gray. It is highly unlikely that if 'Bernhard is a rhino' or 'Jason is bored' or both then Greg is a lion.
hypothesis: It is likely that either 'Jason is bored' or 'Greg is a lion' but not both.
valid_hypothesis: Chances are slight that either 'Jason is bored' or 'Greg is a lion' but not both.
invalid_hypothesis: It is likely that either 'Jason is bored' or 'Greg is a lion' but not both.
problog: 
    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.
    0.1::factB.
    0.1::factC.
    %hop1
    0.8::factX:-and(factC,factA).
    0.02::factY:-xor(factA,factC).
    0.05::factZ:-or(factA,factB).
  
    %hop2
    conclusion:-xor(factB,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Jason is bored' or 'Greg is a lion' but not both.