It is probable that Brian is white. It is probably the case that Mary left the football. It is almost certain that Jeff went to the bedroom. It is unlikely that if 'Brian is white' or 'Jeff went to the bedroom' or both then Lily is a frog. There is little chance that if either 'Jeff went to the bedroom' or 'Brian is white' but not both then John took the milk. We believe that if 'Jeff went to the bedroom and Mary left the football' then Bernhard is gray.
It is certain that 'Mary left the football' or 'Jeff went to the bedroom' or both.
It is certain that 'Mary left the football' or 'Jeff went to the bedroom' or both.
There is almost no chance that 'Mary left the football' or 'Jeff went to the bedroom' or both.

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

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

  query(conclusion).
  
'Mary left the football' or 'Jeff went to the bedroom' or both.