context: We believe that Brian is a rhino. There is a better than even chance that Gertrude is a cat. There is a very good chance that Sandra grabbed the apple. It is probable that if 'Brian is a rhino and Gertrude is a cat' then Greg is a frog. It is probable that if either 'Gertrude is a cat' or 'Brian is a rhino' but not both then Fred dropped the milk. Chances are slight that if either 'Gertrude is a cat' or 'Sandra grabbed the apple' but not both then Mary got the football.
hypothesis: Chances are about even that 'Sandra grabbed the apple and Gertrude is a cat'.
valid_hypothesis: Chances are about even that 'Sandra grabbed the apple and Gertrude is a cat'.
invalid_hypothesis: It is almost certain that 'Sandra grabbed the apple and Gertrude is a cat'.
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
    0.75::factA.
    0.6::factB.
    0.8::factC.
    %hop1
    0.7::factX:-and(factA,factB).
    0.7::factY:-xor(factB,factA).
    0.1::factZ:-xor(factB,factC).
  
    %hop2
    conclusion:-and(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Sandra grabbed the apple and Gertrude is a cat'.