"In the presented system, only simple mouse events are listened for, and input from the keyboard is only listened for if it results in a response from the browser (for example a page load, or a button command). As with making combination event handlers more expressive (as discussed in section 7.1.2), this would be a careful trade-off between flexibility, ease-of-use and keeping the XML schema simple.
There is also scope for adding load and unload handlers for the XML file itself. Currently this cannot be listened for and the browser may have to be restarted to trigger a session start event for the experiment."
~ Mitchell, R. (2008)