context: It is probable that Mary went to the garden. It is highly unlikely that Fred moved to the office. We believe that Julius is a swan. It is highly unlikely that if either 'Mary went to the garden' or 'Julius is a swan' but not both then John left the milk. It is certain that if 'Fred moved to the office and Mary went to the garden' then Lily is a lion. It is unlikely that if 'Mary went to the garden and Fred moved to the office' then Yann is tired.
hypothesis: It is likely that either 'Mary went to the garden' or 'Fred moved to the office' but not both.
valid_hypothesis: It is likely that either 'Mary went to the garden' or 'Fred moved to the office' but not both.
invalid_hypothesis: We doubt that either 'Mary went to the garden' or 'Fred moved to the office' 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
    0.7::factA.
    0.05::factB.
    0.75::factC.
    %hop1
    0.05::factX:-xor(factA,factC).
    1.0::factY:-and(factB,factA).
    0.2::factZ:-and(factA,factB).
  
    %hop2
    conclusion:-xor(factA,factB).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Mary went to the garden' or 'Fred moved to the office' but not both.