Identifying to which note a grace note is attached

Good afternoon,

Firstly, my comprehension of music notation is not extensive, so please 
forgive me if I make any clearly wrong assumptions.

When using notation software, we can add a grace note or appoggiatura to 
either the start of a note or after it.
At this point, we can decide to link the notes with a tie, a slur or 
nothing as in this manner.


I have two questions :

 1. In MusicXML, how can I detect which to note the grace note is
    attached since there is no tie or slur ?
 2. Is this layout correct specifically for the second scenario ?

Best regards
Simon Giddings