It is probably not the case that Brian is yellow. There is a very good chance that Mary went to the office. We believe that John grabbed the apple. Chances are about even that if 'John grabbed the apple' or 'Mary went to the office' or both then Lily is green. Chances are slight that if 'Mary went to the office and Brian is yellow' then Greg is yellow. We doubt that if either 'John grabbed the apple' or 'Mary went to the office' but not both then Sandra got the football.
It is almost certain that 'John grabbed the apple' or 'Mary went to the office' or both.
It is almost certain that 'John grabbed the apple' or 'Mary went to the office' or both.
We doubt that 'John grabbed the apple' or 'Mary went to the office' 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
  0.25::factA.
  0.8::factB.
  0.75::factC.
  %hop1
  0.5::factX:-or(factC,factB).
  0.1::factY:-and(factB,factA).
  0.2::factZ:-xor(factC,factB).

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

  query(conclusion).
  
'John grabbed the apple' or 'Mary went to the office' or both.