Where are the schemas for XML files on an Android project?
Generally, defining a namespace in XML doesn't has to be a real existing URL but just a world wide unique String (therefore one prefers using their own URLs). Of course, it's nice if this URL contains the XML-schema (or worse, DTD). It would be also very nice if someone would create Android Ressource Schemata. I could help him as a bachelor thesis in CS. - Prof. Solymosi, Berlin
The XML schema doesn't seem to be documented, but there is a useful list of all the layout objects and their permitted attributes here:
http://developer.android.com/reference/android/R.styleable.html#lfields