It is probably the case that Mary went to the office. Chances are about even that Antoine is thirsty. It is improbable that Bernhard is a swan. It is certain that if 'Mary went to the office and Bernhard is a swan' then John dropped the milk. It is almost certain that if either 'Bernhard is a swan' or 'Antoine is thirsty' but not both then Brian is yellow. There is a very good chance that if 'Mary went to the office' or 'Antoine is thirsty' or both then Lily is a frog.
It is probably not the case that 'Bernhard is a swan' or 'Mary went to the office' or both.
We believe that 'Bernhard is a swan' or 'Mary went to the office' or both.
It is probably not the case that 'Bernhard is a swan' or 'Mary went to the office' 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.
  0.5::factB.
  0.1::factC.
  %hop1
  1.0::factX:-and(factA,factC).
  0.95::factY:-xor(factC,factB).
  0.8::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Bernhard is a swan' or 'Mary went to the office' or both.