How to validate against schema for namespace, not complete document? - validation

Question

I have a document like this:
<d:block xmlns:d="D" xmlns:b="B" xmlns="default" name="popover">
<d:description>...</d:description>
<d:sample>
<b:popover>
...some b:stuff...
</b:popover>
</d:sample>
</d:block>
Schema for this document looks like:
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
<start>
<element name="block" ns="D">
<attribute name="name"/>
<element name="description">
<text/>
</element>
<element name="sample">
<ref name="anything"/>
</element>
</element>
</start>
<define name="anything">
<element>
<anyName>
<except>
<nsName ns="D"/>
</except>
</anyName>
<zeroOrMore>
<choice>
<attribute>
<anyName/>
</attribute>
<text/>
<ref name="anything"/>
</choice>
</zeroOrMore>
</element>
</define>
</grammar>
"Anything" literally means anything but D-namespaced.
And I want to create another schema for B namespace to use it against any arbitrary XML containing B:namespace.
How to create Schema for the namespace, not for the complete document?
Can't get this.

Answer 1

A kind of schema like that should work. You just have to define the elements for B namespace in the define element named BElements.
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
<start>
<ref name="anythingOrB"/>
</start>
<define name="anythingOrB">
<choice>
<ref name="BElements"/>
<ref name="anythingExceptB"/>
</choice>
</define>
<define name="anythingExceptB">
<element>
<anyName>
<except>
<nsName ns="B"/>
</except>
</anyName>
<zeroOrMore>
<choice>
<attribute>
<anyName/>
</attribute>
<text/>
<ref name="anythingOrB"/>
</choice>
</zeroOrMore>
</element>
</define>
<define name="BElements">
<choice>
<element name="elt1" ns="B">
<empty/>
</element>
<element name="elt2" ns="B">
<empty/>
</element>
</choice>
</define>
</grammar>