[relaxng-user] including XLink attributes in RNG schema question

[Helka Folch]

Hello,
I'm trying to write a Relax-ng schema to describe elements which have 
xlink href attributes attached to them. For instance, I want the schema 
to describe the following :

<node xmlns:xlink="http://www.w3.org/1999/xlink" >
  <use xlink:href="http://wwwhatever"/>
</node>

So, in my schema I include the RNG  schema for XLink (xlink.rng) and the 
reference to Xlink attributes :


<grammar xmlns="http://relaxng.org/ns/structure/1.0">
<include href="xlink.rng"/>
<start>
<element name="node" >
         <element name="use">
                  <empty/>
                  <ref name="XLINK.simple.attlist"/>
          </element >
</element >
</start>
</grammar>


If I understand correctly, there are no default or fixed values for 
attribute definitions in RNG schemas. Does that mean that the required 
XLink attribute 'type' has to be specified on each element of the 
instance document that also uses the XLink attribute href,  for it to be 
valid?, like this :

<use xlink:href="http://wwwhatever" xlink:type="simple" />

My second question, concerns the fact that I would like the 'href' 
attribute to be a required attribute of the 'use' element. However, in 
the RNG schema for XLink the href attribute (XLINK.href.attrib) is 
defined as optional, so when I include the definition in my schema I 
import the optionality.

Is there another way of including XLink attributes that wouldn't require 
specifying the xlink 'type' attribute in the instance document and 
would  allow me to define the xlink href  attribute as required in the 
schema, while conforming to the XLink spec?


Many thanks,

Helka Folch