Declarative Approach

XML is used to represent several aspects of time in SMIL:

Synchronization
Hierarchy of seq and par operators, attributes (begin, dur...)
Animation
Specify how the value of an attribute changes over the time:
<rect x="0" y="0" width="80px" height="50px">
   <animate attributeName="x" from="0" to="500"
            dur="3s"/>
</rect>
Applications
HTML+SMIL (IE 6), SVG animation, Timed Text