There is a better than even chance that Mary went to the office. There is a better than even chance that Julius is a lion. There is little chance that John took the apple. It is impossible that if 'John took the apple' or 'Julius is a lion' or both then Bill left the milk. It is probable that if either 'John took the apple' or 'Julius is a lion' but not both then Lily is a swan. It is highly unlikely that if either 'Mary went to the office' or 'John took the apple' but not both then Greg is a rhino.
We believe that 'Bill left the milk and Lily is a swan'.
It is impossible that 'Bill left the milk and Lily is a swan'.
We believe that 'Bill left the milk and Lily is a swan'.

  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
  0.6::factA.
  0.6::factB.
  0.1::factC.
  %hop1
  0.0::factX:-or(factC,factB).
  0.7::factY:-xor(factC,factB).
  0.05::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Bill left the milk and Lily is a swan'.