It is unlikely that John discarded the milk. It is unlikely that Julius is a frog. It is impossible that Yann is bored. There is a very good chance that if 'John discarded the milk' or 'Yann is bored' or both then Greg is a lion. It is almost certain that if 'Julius is a frog and Yann is bored' then Mary got the football. There is a very good chance that if 'Yann is bored and John discarded the milk' then Brian is a rhino.
We doubt that 'John discarded the milk' or 'Yann is bored' or both.
We doubt that 'John discarded the milk' or 'Yann is bored' or both.
It is almost certain that 'John discarded the milk' or 'Yann is bored' 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
  0.2::factA.
  0.2::factB.
  0.0::factC.
  %hop1
  0.8::factX:-or(factA,factC).
  0.95::factY:-and(factB,factC).
  0.8::factZ:-and(factC,factA).

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

  query(conclusion).
  
'John discarded the milk' or 'Yann is bored' or both.