context: Chances are about even that Jessica is a mouse. It is probable that John discarded the apple. Chances are about even that Brian is a rhino. It is highly likely that if either 'John discarded the apple' or 'Brian is a rhino' but not both then Sumit is tired. It is probably the case that if 'John discarded the apple and Jessica is a mouse' then Mary went to the bedroom. It is probable that if 'Brian is a rhino and John discarded the apple' then Greg is a swan.
hypothesis: It is probable that either 'Brian is a rhino' or 'Greg is a swan' but not both.
valid_hypothesis: It is probably not the case that either 'Brian is a rhino' or 'Greg is a swan' but not both.
invalid_hypothesis: It is probable that either 'Brian is a rhino' or 'Greg is a swan' 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
    0.5::factA.
    0.7::factB.
    0.5::factC.
    %hop1
    0.9::factX:-xor(factB,factC).
    0.7::factY:-and(factB,factA).
    0.7::factZ:-and(factC,factB).
  
    %hop2
    conclusion:-xor(factC,factZ).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is a rhino' or 'Greg is a swan' but not both.