I need to implement a kind of template processor in which simple
constructs like this:

(define-activity
 :name activity-name
 :subactivities subactivity-list)

get translated into a bunch of replacement s-expressions.

I have a simple define-syntax macro definition that seems to work on forms
when they appear in the same Scheme code as the define-syntax form or are
entered interactively after the macro is defined.

I thought that by using (load ...) in the scope of a (let-syntax ...) form
that includes the same macro definition would apply the macro to the
expressions loaded from the file, but I get diagnostics
that "define-activity" is undefined.

What is the general technique for implementing template-driven data ->
data transformations (as opposed to form -> form transformations).

I'll admit, as if it's necessary, that this is my first foray into Scheme
and the last time I did any Lisp it was Common Lisp and quite a long time
ago. So while I understand Lisp basics, I'm pretty naive at this point
with Scheme.

Thanks.