Looking at [1] and the key value database described there, it would need some key coordination mechanism to make use of the system database. For instance, a way

Looking at [1] and the key value database described there, it would need some key coordination mechanism to make use of the system database. For instance, a way for an app to say that a document it stores is either directly of a given type or implements the interface (ex: an email or a music data), so that other apps can use this document. So the type field would refer to a standardized type like a uuid associated with some type of data or a URI (like in RDF). Also, it can have some mechanism for other types to implement the interface or extend existing types and for users to create new types just like we can register urls today. Having a database with standardized interfaces for documents replace a filesystem is a really important feature mentioned in the article. It will allow the development of many useful apps like the itunes or email examples. Also, this is not specific to any OS can be standardized independently and implemented on current OSes we use by having some extension which stores metadata along with a file.