There is little chance that Brian is yellow. It is certain that Lily is green. It is highly unlikely that Bill went to the bedroom. There is little chance that if 'Bill went to the bedroom and Lily is green' then Fred left the football. It is probable that if 'Bill went to the bedroom' or 'Lily is green' or both then Mary got the milk. Chances are slight that if 'Brian is yellow and Lily is green' then Emily is a wolf.
It is impossible that 'Fred left the football and Bill went to the bedroom'.
It is impossible that 'Fred left the football and Bill went to the bedroom'.
Chances are about even that 'Fred left the football and Bill went to the bedroom'.

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

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

  query(conclusion).
  
'Fred left the football and Bill went to the bedroom'.