context: It is unlikely that Gertrude is a sheep. We doubt that Lily is a swan. It is probably the case that John went to the office. It is probable that if 'Gertrude is a sheep and John went to the office' then Fred left the football. It is probably the case that if 'Gertrude is a sheep and Lily is a swan' then Greg is green. We doubt that if either 'John went to the office' or 'Lily is a swan' but not both then Mary moved to the garden.
hypothesis: There is a very good chance that either 'Lily is a swan' or 'Fred left the football' but not both.
valid_hypothesis: It is probably not the case that either 'Lily is a swan' or 'Fred left the football' but not both.
invalid_hypothesis: There is a very good chance that either 'Lily is a swan' or 'Fred left the football' 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
    0.2::factA.
    0.2::factB.
    0.7::factC.
    %hop1
    0.7::factX:-and(factA,factC).
    0.7::factY:-and(factA,factB).
    0.2::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-xor(factB,factX).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Lily is a swan' or 'Fred left the football' but not both.