Lisper was replying to the OP who suggested using Make for general workflows. Make falls apart when your workflow doesn't naturally involve file modification tasks.

With regard to my last comment (the problem with small changes in a file resulting in full-system recompilation), see Tup. It maintains a database of what's happened. So when foo.c is altered it will regenerate foo.o. But if foo.o is not changed, you can set it up to not do anything else. The database is updated to reflect that the current foo.c maps to the current foo.o, and no tasks depending on foo.o will be executed. Tup also handles the case of multiple outputs from a task. There are probably others that do this, it's the one I found that worked well for my (filesystem-based) workflows.

With regard to general workflows (that involve non-filesystem activities), you have to have a workflow system that registers when events happened and other traits to determine whether or not to reexecute all or part of the workflow.