Chances are about even that Lily is green. It is unlikely that Gertrude is a cat. It is certain that Mary went to the garden. It is certain that if 'Mary went to the garden and Lily is green' then Sandra dropped the milk. It is probably the case that if 'Gertrude is a cat and Lily is green' then Greg is gray. We doubt that if 'Gertrude is a cat and Lily is green' then Julius is yellow.
There is a better than even chance that 'Julius is yellow and Greg is gray'.
There is almost no chance that 'Julius is yellow and Greg is gray'.
There is a better than even chance that 'Julius is yellow and Greg is gray'.

  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.
  0.2::factB.
  1.0::factC.
  %hop1
  1.0::factX:-and(factC,factA).
  0.7::factY:-and(factB,factA).
  0.2::factZ:-and(factB,factA).

  %hop2
  conclusion:-and(factZ,factY).

  query(conclusion).
  
'Julius is yellow and Greg is gray'.