context: It is probable that Mary got the football. We believe that Sandra left the milk. It is probably the case that Greg is a rhino. It is probably not the case that if 'Mary got the football and Greg is a rhino' then John discarded the apple. There is almost no chance that if 'Sandra left the milk' or 'Greg is a rhino' or both then Bill went to the kitchen. We believe that if 'Mary got the football and Greg is a rhino' then Bernhard is a frog.
hypothesis: It is impossible that 'John discarded the apple' or 'Greg is a rhino' or both.
valid_hypothesis: It is probably the case that 'John discarded the apple' or 'Greg is a rhino' or both.
invalid_hypothesis: It is impossible that 'John discarded the apple' or 'Greg is a rhino' or 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
    0.7::factA.
    0.75::factB.
    0.7::factC.
    %hop1
    0.25::factX:-and(factA,factC).
    0.02::factY:-or(factB,factC).
    0.75::factZ:-and(factA,factC).
  
    %hop2
    conclusion:-or(factX,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'John discarded the apple' or 'Greg is a rhino' or both.