RelaxNG is absolute crap, and it attempts to regress the world back to something similar to DTDs. In fact, an equivalent DTD would look very similar to the RelaxNG compact you posted. XML schema is not perfect (and sometimes a little rigid, compared to better (and fundamentally different) approaches such as RDF/OWL.

What you are doing, is constraining the structure of a document (whoopy dooh). What XML Schema is, is an object-oriented data language with classes, specialisation, polymorphism, etc. If you are an XML document writer, you might not see the benefit of this. If you are a designer or a developer (and have to, for example, transfer the state of an object between a Java object representation, and XML) you will understand. With XML Schema, an xml document becomes an instance of a class (an object).

XML Schema is conceptually at a whole level above RelaxNG and DTD, and RDF/OWL is - again - conceptually at a whole level above XML Schema.
You clearly have no idea what you're talking about - please research your facts before asserting them.