    <!--
                Copyright: Copyright 1998-2001 W3C (MIT, INRIA, 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
    disappear.
    -->
    <smil xmlns="http://www.w3.org/2001/SMIL20/Language">
    <body>
            <par>
                    <par id="par1" begin="10s" dur="10s">
                            <par id="par2" begin="-5s" dur="10s">
                                    <img id="smile" begin="0s" dur="5s"
    src="../images/smile.jpg"/>
                                    <img id="frown" begin="0s" dur="10s"
    src="../images/frown.jpg"/>
                            </par>
                    </par>
                    <video id="video1" begin="smile.begin" dur="10s"
    src="../videos/nasa.qt"/>
                    <video id="video2" begin="frown.begin" dur="10s"
    src="../videos/nasa.qt"/>
            </par>
    </body>
    </smil>