It is probable that Greg is a frog. It is certain that John dropped the apple. It is unlikely that Fred moved to the office. There is almost no chance that if either 'Greg is a frog' or 'Fred moved to the office' but not both then Julius is a rhino. There is little chance that if 'John dropped the apple and Greg is a frog' then Lily is white. It is highly likely that if 'Fred moved to the office and Greg is a frog' then Mary went to the hallway.
It is probably not the case that 'Greg is a frog' or 'Lily is white' or both.
It is probable that 'Greg is a frog' or 'Lily is white' or both.
It is probably not the case that 'Greg is a frog' or 'Lily is white' 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.
  0.2::factC.
  %hop1
  0.02::factX:-xor(factA,factC).
  0.1::factY:-and(factB,factA).
  0.9::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Greg is a frog' or 'Lily is white' or both.