context: We believe that Emily is a mouse. Chances are about even that Winona is a sheep. It is probably the case that Lily is a lion. There is little chance that if 'Emily is a mouse' or 'Lily is a lion' or both then Mary got the apple. It is highly likely that if either 'Emily is a mouse' or 'Lily is a lion' but not both then Greg is a frog. There is almost no chance that if 'Lily is a lion' or 'Winona is a sheep' or both then John discarded the milk.
hypothesis: It is highly unlikely that 'Greg is a frog and Mary got the apple'.
valid_hypothesis: It is highly unlikely that 'Greg is a frog and Mary got the apple'.
invalid_hypothesis: It is probable that 'Greg is a frog and Mary got the apple'.
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.
    0.5::factB.
    0.7::factC.
    %hop1
    0.1::factX:-or(factA,factC).
    0.9::factY:-xor(factA,factC).
    0.02::factZ:-or(factC,factB).
  
    %hop2
    conclusion:-and(factY,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a frog and Mary got the apple'.