It is probable that Sandra left the milk. We doubt that Brian is yellow. Chances are slight that John went to the hallway. There is a better than even chance that if 'Brian is yellow and Sandra left the milk' then Bernhard is a swan. It is certain that if 'John went to the hallway' or 'Brian is yellow' or both then Fred moved to the office. We doubt that if 'Brian is yellow' or 'John went to the hallway' or both then Daniel dropped the apple.
It is probably the case that 'John went to the hallway and Brian is yellow'.
There is almost no chance that 'John went to the hallway and Brian is yellow'.
It is probably the case that 'John went to the hallway and Brian is yellow'.

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

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

  query(conclusion).
  
'John went to the hallway and Brian is yellow'.