It is almost certain that John moved to the office. It is likely that Lily is a lion. We believe that Mary took the milk. It is probably the case that if 'Lily is a lion and John moved to the office' then Greg is white. It is highly unlikely that if 'John moved to the office and Lily is a lion' then Brian is yellow. There is little chance that if 'Mary took the milk' or 'Lily is a lion' or both then Fred is in the school.
It is probably not the case that 'Greg is white' or 'John moved to the office' or both.
It is almost certain that 'Greg is white' or 'John moved to the office' or both.
It is probably not the case that 'Greg is white' or 'John moved 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
  0.95::factA.
  0.7::factB.
  0.75::factC.
  %hop1
  0.7::factX:-and(factB,factA).
  0.05::factY:-and(factA,factB).
  0.1::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Greg is white' or 'John moved to the office' or both.