It is probably the case that Greg is a rhino. It is probably not the case that John picked up the milk. It is likely that Brian is yellow. We believe that if 'Greg is a rhino' or 'John picked up the milk' or both then Lily is a lion. It is certain that if 'Brian is yellow' or 'John picked up the milk' or both then Bernhard is a swan. It is highly likely that if 'Greg is a rhino and Brian is yellow' then Mary went to the garden.
It is highly unlikely that 'Lily is a lion' or 'John picked up the milk' or both.
There is a better than even chance that 'Lily is a lion' or 'John picked up the milk' or both.
It is highly unlikely that 'Lily is a lion' or 'John picked up the milk' 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.
  0.25::factB.
  0.7::factC.
  %hop1
  0.75::factX:-or(factA,factB).
  1.0::factY:-or(factC,factB).
  0.9::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Lily is a lion' or 'John picked up the milk' or both.