[galaxy-dev] What are these called and where can I learn about them...

Hi all Apologies if I am in the wrong channel to post this. I have been using Galaxy for a couple of months now and I'm still finding my way around the mass of info Some of the XML config file tags have a string interpolation type of variable such as ${tool.name} in: label="${tool.name} on ${on_string}: insertions" Where can I read up more on these and learn what others exist? I tried http://wiki.galaxyproject.org/Admin/Tools/ToolConfigSyntax and found a titbit at the end of the page but nothing more. Thanx gordon