Initialize items in shell's RuntimeContext?

[Steve Storck]

I would like the shell to indicate the current context of operations in my application.  I don't mean to use such an overloaded term (context) but the currently selected "thing" in my app will be what certain commands will operate on.  When I'm setting the active "thing" in a command, I can put an item into the context, but how can I initialize that RuntimeContext variable before I ever run the command?