comments from Hixie: "I've nothing against formalisms being used non-normatively, since they sometimes can be useful for making things clearer than prose. However, normatively they are only useful, IMHO, if they are comprehensive, and a comprehensive formalism would be incomprehensible if used to describe HTML5's rules... if the document is normative and uses formalisms, then the current language used will likely be found to be unsuitable, and thus I would recommend finding a better language to use (or developing one specifically for this purpose)."