Hmm, according to Stan Kitsis there is at least 6 ways to associate an XML Schema with an XML document in Visual Studio 2005:
1. Schemas Property on your XML documentIs it actually sane? Now I can easily imagine a situation when I cannot be sure against which XML Schema file I'm validating my documents. Lots of flexibility, too much or just right? What is your take?
2. Inline inside your XML document
3. xsi:schemaLocation or xsi:noNamespaceSchemaLocation attributes in your XML document
4. Open Document Window.
5. Anywhere in your current Project
6. In the Schema Cache Directory or from a Schema Catalog file.
Schemas property in the Property window will always show which schemas are used for validation. If you don't like what the XML Editor picked, you can always change the property.
Yeah, should be some simple way to figure out which schema is actually gonna be used.
About RDF - I don't think so. Go download VS SDK and implement it yourself :)
There should be some linking to the Schema, like a SmartTag on the xmlns "View this Schema".
Off-Topic: is there any way Microsoft will implement RDF-Support in VisualStudio? (especially designer-support for RDF-Schema, editor-support for the non-xml-dialects (like notation3) and of course System.Rdf)