context: It is improbable that Fred is in the office. It is highly unlikely that Brian is a swan. It is impossible that Mary went to the garden. It is almost certain that if 'Brian is a swan and Mary went to the garden' then Julius is gray. Chances are about even that if either 'Brian is a swan' or 'Mary went to the garden' but not both then Sandra got the milk. It is probably the case that if either 'Mary went to the garden' or 'Brian is a swan' but not both then John put down the apple.
hypothesis: It is improbable that 'Fred is in the office' or 'Julius is gray' or both.
valid_hypothesis: It is improbable that 'Fred is in the office' or 'Julius is gray' or both.
invalid_hypothesis: It is almost certain that 'Fred is in the office' or 'Julius is gray' 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
    0.1::factA.
    0.05::factB.
    0.0::factC.
    %hop1
    0.95::factX:-and(factB,factC).
    0.5::factY:-xor(factB,factC).
    0.7::factZ:-xor(factC,factB).
  
    %hop2
    conclusion:-or(factA,factX).
  
    query(conclusion).
    
hypothesis_assertion: 'Fred is in the office' or 'Julius is gray' or both.