It is probably the case that Mary put down the apple. It is probable that Bernhard is a lion. It is improbable that John got the milk. It is unlikely that if 'Bernhard is a lion' or 'John got the milk' or both then Jason is tired. There is a very good chance that if 'John got the milk and Mary put down the apple' then Sumit is thirsty. It is unlikely that if either 'Bernhard is a lion' or 'John got the milk' but not both then Greg is gray.
We believe that 'John got the milk' or 'Mary put down the apple' or both.
We believe that 'John got the milk' or 'Mary put down the apple' or both.
It is unlikely that 'John got the milk' or 'Mary put down the apple' 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.
  0.7::factB.
  0.1::factC.
  %hop1
  0.2::factX:-or(factB,factC).
  0.8::factY:-and(factC,factA).
  0.2::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'John got the milk' or 'Mary put down the apple' or both.