It is highly unlikely that Brian is yellow. It is probable that Lily is a swan. It is probably not the case that Bernhard is green. It is almost certain that if 'Lily is a swan and Brian is yellow' then Greg is gray. It is likely that if either 'Lily is a swan' or 'Bernhard is green' but not both then John went to the office. It is unlikely that if either 'Lily is a swan' or 'Brian is yellow' but not both then Sandra dropped the milk.
It is probable that 'Brian is yellow' or 'Lily is a swan' or both.
It is probable that 'Brian is yellow' or 'Lily is a swan' or both.
It is impossible that 'Brian is yellow' or 'Lily is a swan' or both.

  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
  0.05::factA.
  0.7::factB.
  0.25::factC.
  %hop1
  0.95::factX:-and(factB,factA).
  0.7::factY:-xor(factB,factC).
  0.2::factZ:-xor(factB,factA).

  %hop2
  conclusion:-or(factA,factB).

  query(conclusion).
  
'Brian is yellow' or 'Lily is a swan' or both.