Chances are about even that Emily is a sheep. There is little chance that Mary dropped the milk. It is probably not the case that Greg is a frog. It is probably not the case that if 'Mary dropped the milk' or 'Emily is a sheep' or both then Julius is a lion. It is probably not the case that if 'Mary dropped the milk' or 'Emily is a sheep' or both then John took the football. Chances are slight that if 'Mary dropped the milk' or 'Greg is a frog' or both then Lily is a swan.
It is highly unlikely that 'Emily is a sheep' or 'Mary dropped the milk' or both.
There is a better than even chance that 'Emily is a sheep' or 'Mary dropped the milk' or both.
It is highly unlikely that 'Emily is a sheep' or 'Mary dropped the milk' 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
  0.5::factA.
  0.1::factB.
  0.25::factC.
  %hop1
  0.25::factX:-or(factB,factA).
  0.25::factY:-or(factB,factA).
  0.1::factZ:-or(factB,factC).

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

  query(conclusion).
  
'Emily is a sheep' or 'Mary dropped the milk' or both.