It is probable that Brian is a rhino. There is a better than even chance that John put down the apple. We doubt that Bernhard is a swan. It is likely that if 'Brian is a rhino and Bernhard is a swan' then Winona is a wolf. It is highly unlikely that if 'John put down the apple' or 'Bernhard is a swan' or both then Sandra took the football. It is highly unlikely that if 'Brian is a rhino and Bernhard is a swan' then Mary dropped the apple.
It is impossible that 'Brian is a rhino and Mary dropped the apple'.
It is impossible that 'Brian is a rhino and Mary dropped the apple'.
There is a better than even chance that 'Brian is a rhino and Mary dropped the apple'.

  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
  0.7::factA.
  0.6::factB.
  0.2::factC.
  %hop1
  0.7::factX:-and(factA,factC).
  0.05::factY:-or(factB,factC).
  0.05::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Brian is a rhino and Mary dropped the apple'.