In general, I agree, one would only want a single element of each type. But in other cases it would be too restrictive to have such a... er... restriction. A book can have several forewords, and definitely multiple (e.g.) other.map instances, each of them would be identified with a different "title" attribute. At the end of it, it's up to the reading system to properly handle these cases, and I'm sure all of them will assume there's only a toc and a cover (I don't even know a RS that deals with multiple titles or languages
), so even if it's allowed by the spec, and it could make sense in some cases, I don't think one should expect it to work any time soon...