Chances are about even that Mary picked up the milk. It is almost certain that Lily is a lion. It is unlikely that Greg is yellow. There is a better than even chance that if 'Mary picked up the milk and Greg is yellow' then Brian is white. There is almost no chance that if 'Lily is a lion and Mary picked up the milk' then Gertrude is a mouse. There is a very good chance that if 'Greg is yellow and Mary picked up the milk' then Bernhard is a swan.
Chances are slight that 'Brian is white' or 'Bernhard is a swan' or both.
Chances are slight that 'Brian is white' or 'Bernhard is a swan' or both.
It is probable that 'Brian is white' or 'Bernhard 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
  0.5::factA.
  0.95::factB.
  0.2::factC.
  %hop1
  0.6::factX:-and(factA,factC).
  0.02::factY:-and(factB,factA).
  0.8::factZ:-and(factC,factA).

  %hop2
  conclusion:-or(factX,factZ).

  query(conclusion).
  
'Brian is white' or 'Bernhard is a swan' or both.