Copyright: Copyright 1998-2005  W3C (MIT, ERCIM, Keio), All Rights Reserved.
See http://www.w3.org/Consortium/Legal/.
Author: Aaron Cohen (Intel), Jeff Boston (IBM)
           Version: May 1, 2001
            Module: Timing and Synchronization
           Feature: Interval logic and pruning
         File Name: interval_logic_pruning.smil
  Media Components: 1 QT, 2 JPG
 Expected Behavior: at 5s video1 and video2 appear.
                          at 10s frown begins, 5s into its duration.
                        the smile image ends as the par2 begins and so is not shown.
                          at 15s frown, video1 and video2 all end and
<smil xmlns="http://www.w3.org/2005/SMIL21/Language">
                <par id="par1" begin="10s" dur="10s">
                        <par id="par2" begin="-5s" dur="10s">
                                <img id="smile" begin="0s" dur="5s"
                                <img id="frown" begin="0s" dur="10s"
                <video id="video1" begin="smile.begin" dur="10s"
                <video id="video2" begin="frown.begin" dur="10s"