If one wished to make a TEI application that was more general, that is, relatively easy to customise for different projects, one could make it possible to specify project-specific settings, but a project might also need to set some document-specific settings. Most of this could go into <tagsDecl>, but where would something like "the TOC should limit itself to three <div> levels" go? This could go into the "project-defined formal language" suggested. I would like to ask whether anyone has tried this approach, for instance using feature structures?