context: It is certain that John went to the kitchen. It is probable that Brian is white. It is highly likely that Greg is a swan. It is probably the case that if 'John went to the kitchen and Greg is a swan' then Jessica is a cat. It is improbable that if either 'Greg is a swan' or 'John went to the kitchen' but not both then Julius is a rhino. It is impossible that if 'John went to the kitchen' or 'Greg is a swan' or both then Sandra left the milk.
hypothesis: Chances are about even that either 'Brian is white' or 'Jessica is a cat' but not both.
valid_hypothesis: Chances are about even that either 'Brian is white' or 'Jessica is a cat' but not both.
invalid_hypothesis: There is almost no chance that either 'Brian is white' or 'Jessica is a cat' 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.
    0.7::factB.
    0.9::factC.
    %hop1
    0.7::factX:-and(factA,factC).
    0.1::factY:-xor(factC,factA).
    0.0::factZ:-or(factA,factC).
  
    %hop2
    conclusion:-xor(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is white' or 'Jessica is a cat' but not both.