It is likely that Brian is a frog. It is certain that Greg is yellow. It is probable that Mary went to the hallway. There is little chance that if 'Brian is a frog' or 'Greg is yellow' or both then Bill moved to the office. It is certain that if 'Brian is a frog' or 'Mary went to the hallway' or both then Bernhard is white. It is probable that if either 'Mary went to the hallway' or 'Brian is a frog' but not both then Lily is a rhino.
It is probably not the case that 'Bill moved to the office' or 'Brian is a frog' or both.
We believe that 'Bill moved to the office' or 'Brian is a frog' or both.
It is probably not the case that 'Bill moved to the office' or 'Brian is a frog' 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.
  1.0::factB.
  0.7::factC.
  %hop1
  0.1::factX:-or(factA,factB).
  1.0::factY:-or(factA,factC).
  0.7::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Bill moved to the office' or 'Brian is a frog' or both.