It is probable that Sandra dropped the apple. It is likely that Bill moved to the office. It is almost certain that Brian is yellow. Chances are about even that if either 'Brian is yellow' or 'Sandra dropped the apple' but not both then Mary left the football. It is improbable that if 'Bill moved to the office and Brian is yellow' then John went to the hallway. It is unlikely that if either 'Sandra dropped the apple' or 'Brian is yellow' but not both then Bernhard is a swan.
It is almost certain that 'Mary left the football' or 'Brian is yellow' or both.
It is almost certain that 'Mary left the football' or 'Brian is yellow' or both.
Chances are about even that 'Mary left the football' or 'Brian is yellow' 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
  0.5::factX:-xor(factC,factA).
  0.1::factY:-and(factB,factC).
  0.2::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Mary left the football' or 'Brian is yellow' or both.