SMIL Document Priorities

Is there any way to indicate the priority of each SMIL document? 

For example, SMIL document #1 is scheduled to play from 11/1 - 11/15 during 
8:00 AM to 10:00 AM and SMIL document #2 is scheduled to play from 11/1 - 
11/5 from 8:00 AM - 9:00 AM.

Since these two SMIL schedule documents overlap, we need the capability to 
indicate that SMIL document #2 has a high priority than document #1. During 
the overlapping period, SMIL document #2 should be played in place of document
#1.