It is probable that Jessica is a cat. We believe that Mary dropped the milk. It is unlikely that Bernhard is a swan. Chances are slight that if either 'Bernhard is a swan' or 'Jessica is a cat' but not both then Brian is green. There is a very good chance that if 'Mary dropped the milk' or 'Jessica is a cat' or both then Lily is a rhino. It is probably the case that if either 'Mary dropped the milk' or 'Jessica is a cat' but not both then John went to the office.
We believe that 'Lily is a rhino' or 'Brian is green' or both.
We believe that 'Lily is a rhino' or 'Brian is green' or both.
It is impossible that 'Lily is a rhino' 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.
  0.75::factB.
  0.2::factC.
  %hop1
  0.1::factX:-xor(factC,factA).
  0.8::factY:-or(factB,factA).
  0.7::factZ:-xor(factB,factA).

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

  query(conclusion).
  
'Lily is a rhino' or 'Brian is green' or both.