It is certain that Bernhard is a frog. Chances are about even that Jessica is a sheep. It is highly unlikely that John picked up the apple. It is impossible that if 'Jessica is a sheep and Bernhard is a frog' then Mary left the football. It is probable that if either 'Bernhard is a frog' or 'Jessica is a sheep' but not both then Fred is in the office. We believe that if 'John picked up the apple' or 'Jessica is a sheep' or both then Brian is a lion.
It is highly unlikely that 'John picked up the apple' or 'Bernhard is a frog' or both.
It is certain that 'John picked up the apple' or 'Bernhard is a frog' or both.
It is highly unlikely that 'John picked up the apple' or 'Bernhard is a frog' 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
  1.0::factA.
  0.5::factB.
  0.05::factC.
  %hop1
  0.0::factX:-and(factB,factA).
  0.7::factY:-xor(factA,factB).
  0.75::factZ:-or(factC,factB).

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

  query(conclusion).
  
'John picked up the apple' or 'Bernhard is a frog' or both.