ISL, the Imagine Staging Language, is a language created to make the
generation and manipulation of Imagine 2.0 staging files a whole lot
easier.  If you have ever used the Action editor in earnest, you know
that certain types of operations are easy (such as adding a single
light) while others are not (such as adding more frames and causing
your existing objects to appear in them).

ISL provides an alternative interface to the Action editor.  With ISL,
you can create your stage using the Stage and Action editors as needed,
then convert it to a fairly straightforward ASCII format, edit it as
desired using your favorite text editor, then put it back!  This is of
course the simplest way of using ISL - you could also create stages
programatically.