It is certain that John went to the garden. Chances are slight that Mary moved to the office. Chances are slight that Julius is a lion. There is a better than even chance that if 'Mary moved to the office and Julius is a lion' then Brian is a swan. It is probably not the case that if 'Mary moved to the office and Julius is a lion' then Lily is yellow. It is unlikely that if 'Mary moved to the office' or 'Julius is a lion' or both then Jeff dropped the apple.
It is certain that 'Jeff dropped the apple and Julius is a lion'.
There is almost no chance that 'Jeff dropped the apple and Julius is a lion'.
It is certain that 'Jeff dropped the apple and Julius is a lion'.

  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.
  0.1::factB.
  0.1::factC.
  %hop1
  0.6::factX:-and(factB,factC).
  0.25::factY:-and(factB,factC).
  0.2::factZ:-or(factB,factC).

  %hop2
  conclusion:-and(factZ,factC).

  query(conclusion).
  
'Jeff dropped the apple and Julius is a lion'.