It is almost certain that Bernhard is a lion. It is probably the case that Lily is gray. It is impossible that Julius is a swan. There is little chance that if 'Bernhard is a lion and Julius is a swan' then Greg is white. There is a better than even chance that if 'Lily is gray' or 'Bernhard is a lion' or both then John took the football. It is certain that if 'Lily is gray and Julius is a swan' then Bill went to the office.
There is a very good chance that 'Julius is a swan and Greg is white'.
It is impossible that 'Julius is a swan and Greg is white'.
There is a very good chance that 'Julius is a swan and Greg is white'.

  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
  0.95::factA.
  0.7::factB.
  0.0::factC.
  %hop1
  0.1::factX:-and(factA,factC).
  0.6::factY:-or(factB,factA).
  1.0::factZ:-and(factB,factC).

  %hop2
  conclusion:-and(factC,factX).

  query(conclusion).
  
'Julius is a swan and Greg is white'.