It is unlikely that John went to the garden. Chances are slight that Daniel left the football. It is improbable that Mary discarded the apple. It is probably the case that if either 'Mary discarded the apple' or 'Daniel left the football' but not both then Sandra dropped the milk. There is a very good chance that if 'Mary discarded the apple' or 'John went to the garden' or both then Bernhard is a frog. There is almost no chance that if 'Daniel left the football and Mary discarded the apple' then Brian is gray.
It is probable that 'Bernhard is a frog and Sandra dropped the milk'.
It is highly unlikely that 'Bernhard is a frog and Sandra dropped the milk'.
It is probable that 'Bernhard is a frog and Sandra dropped the milk'.

  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.
  0.1::factB.
  0.1::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.8::factY:-or(factC,factA).
  0.02::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Bernhard is a frog and Sandra dropped the milk'.