There is a very good chance that Mary discarded the milk. There is almost no chance that Fred is in the office. There is little chance that Jeff moved to the garden. Chances are slight that if either 'Jeff moved to the garden' or 'Mary discarded the milk' but not both then Greg is a rhino. There is a better than even chance that if 'Jeff moved to the garden and Mary discarded the milk' then John dropped the apple. We believe that if 'Fred is in the office' or 'Jeff moved to the garden' or both then Bill went to the kitchen.
It is highly unlikely that 'John dropped the apple and Mary discarded the milk'.
It is highly unlikely that 'John dropped the apple and Mary discarded the milk'.
There is a better than even chance that 'John dropped the apple and Mary discarded 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
  0.8::factA.
  0.02::factB.
  0.1::factC.
  %hop1
  0.1::factX:-xor(factC,factA).
  0.6::factY:-and(factC,factA).
  0.75::factZ:-or(factB,factC).

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

  query(conclusion).
  
'John dropped the apple and Mary discarded the milk'.