There should be an object for each standard the developers want to implement.
Suggested Document Objects:
and just about any other structured document that could be built from a PHP object.
Each object should be an extension of a parent Document object. The parent object should provide access to certain Storage objects to allow for saving the end document to a filesystem (local or remote), database, triple-store, or the like. Each child object object would provide the language specific features. Along those lines, it may be best to create XMLDocument, RDFDocument, or similar objects to handle features specific to those meta-languages.
In the database world this would probably end up looking like a View with CRUD features.
The closest thing I’ve found to-date: