Chances are about even that Greg is white. It is highly likely that Bernhard is white. There is little chance that Brian is a lion. It is probably not the case that if 'Brian is a lion' or 'Bernhard is white' or both then Emily is a mouse. It is highly likely that if 'Greg is white and Brian is a lion' then John discarded the milk. Chances are slight that if either 'Bernhard is white' or 'Brian is a lion' but not both then Lily is a rhino.
It is impossible that 'Bernhard is white' or 'Emily is a mouse' or both.
It is highly likely that 'Bernhard is white' or 'Emily is a mouse' or both.
It is impossible that 'Bernhard is white' or 'Emily is a mouse' 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.
  0.9::factB.
  0.1::factC.
  %hop1
  0.25::factX:-or(factC,factB).
  0.9::factY:-and(factA,factC).
  0.1::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Bernhard is white' or 'Emily is a mouse' or both.