It is improbable that Gertrude is a mouse. Chances are slight that Lily is white. It is probable that John went to the hallway. There is little chance that if 'Gertrude is a mouse and Lily is white' then Mary dropped the milk. There is a very good chance that if either 'John went to the hallway' or 'Lily is white' but not both then Fred moved to the office. It is almost certain that if 'Lily is white' or 'John went to the hallway' or both then Julius is gray.
There is a better than even chance that 'Lily is white and Gertrude is a mouse'.
There is almost no chance that 'Lily is white and Gertrude is a mouse'.
There is a better than even chance that 'Lily is white and Gertrude is a mouse'.

  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.
  0.1::factB.
  0.7::factC.
  %hop1
  0.1::factX:-and(factA,factB).
  0.8::factY:-xor(factC,factB).
  0.95::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Lily is white and Gertrude is a mouse'.