I wrote a simple DSL that she can use. She knows some HTML and basic scripting, so as long as the rules are easy to express and she has good examples, she can tweak the rules herself.

I just hacked up a little shallow embedding via lex/yacc, using the C API. It's not pretty, but it was put together quickly to solve a problem.

As for typical constraints, there needs to be people on certain desks at certain times. People have to take breaks between N and M hours after starting. People have off-desk time that they use to perform other tasks that must be managed and must be contiguous. People have different numbers of hours they have to work, and a finite amount of time that they are allowed to be on a particular desk on a given day or week.