Hi,
For your On Demand environments you will be able to reach either the Development, Test or Production directory using the following path:
/fs0/clarity1/share
Therefore as a GEL example, you could use:
<core:set var="rootDir" value="/fs0/clarity1/share" />
<core:set var="paramFile">${rootDir}${file.separator}param.xml</core:set>
<gel:parse file="${paramFile}" var="params"/>
Regards
Steve