We doubt that Bernhard is a rhino. It is improbable that Gertrude is a mouse. It is certain that John put down the apple. Chances are about even that if either 'Bernhard is a rhino' or 'Gertrude is a mouse' but not both then Julius is a frog. There is little chance that if 'Bernhard is a rhino and John put down the apple' then Mary went to the hallway. It is likely that if 'Gertrude is a mouse and Bernhard is a rhino' then Jessica is a sheep.
It is impossible that 'Mary went to the hallway and Julius is a frog'.
It is impossible that 'Mary went to the hallway and Julius is a frog'.
There is a better than even chance that 'Mary went to the hallway and Julius is a frog'.

  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.
  1.0::factC.
  %hop1
  0.5::factX:-xor(factA,factB).
  0.1::factY:-and(factA,factC).
  0.7::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Mary went to the hallway and Julius is a frog'.