The values 0 and 1 are no longer allowed. These are meant to request of implementers a report if a feature has proved difficult to implement or has some flaw. Probably some of these will change after the review of feedback from the Candidate Release. Authors and trainers may want to treat these sections with a little more caution than other parts. If one view is that null has no place, another is that nulls represent a particular case of the more general phenomenon of exceptions to data, which should be supported.
Local names are bindings between an element name and a type scoped to a parent type.
For example a mouse subelement of a computer element could have a different type than a mouse subelement of a catfood element. Others say it reduces complexity because it removes a distinction between attributes and elements. The feature has been requested to aid mappings to database schemas and programming languages. The main issue is what the best default values should be. Indeed, the whole area of how to construct schemas from existing schemas is one where the Working Group requires the results of field trials before ultimately recommending the current methods.