There is little chance that Mary dropped the apple. We believe that Brian is a rhino. Chances are slight that Bill went to the kitchen. It is highly unlikely that if 'Brian is a rhino and Mary dropped the apple' then John is in the garden. It is highly unlikely that if 'Brian is a rhino and Mary dropped the apple' then Julius is yellow. It is highly likely that if either 'Bill went to the kitchen' or 'Brian is a rhino' but not both then Greg is gray.
It is certain that 'John is in the garden and Brian is a rhino'.
It is impossible that 'John is in the garden and Brian is a rhino'.
It is certain that 'John is in the garden and Brian is a rhino'.

  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
  0.1::factA.
  0.75::factB.
  0.1::factC.
  %hop1
  0.05::factX:-and(factB,factA).
  0.05::factY:-and(factB,factA).
  0.9::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'John is in the garden and Brian is a rhino'.