<?xml version="1.0"?> 
<param xml:id='expression_validation_2'> 
  <time_resolution>60</time_resolution> 
  <get> 
    <amdaParam name='density'/> 
    <amdaParam name='speed'/>
  </get> 
  <process description="bad expression">$density * $speed + ($density^2 - 1.0 / $speed</process> 
  <output/> 
</param>