It is likely that Bernhard is white. It is improbable that Lily is yellow. Chances are about even that Brian is green. There is a very good chance that if 'Lily is yellow and Bernhard is white' then Gertrude is a wolf. There is a better than even chance that if 'Brian is green and Bernhard is white' then Greg is a swan. It is likely that if 'Lily is yellow and Brian is green' then Mary went to the garden.
It is highly unlikely that 'Mary went to the garden' or 'Brian is green' or both.
Chances are about even that 'Mary went to the garden' or 'Brian is green' or both.
It is highly unlikely that 'Mary went to the garden' or 'Brian is green' 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
  0.7::factA.
  0.1::factB.
  0.5::factC.
  %hop1
  0.8::factX:-and(factB,factA).
  0.6::factY:-and(factC,factA).
  0.7::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Mary went to the garden' or 'Brian is green' or both.