Defining a schema over another schema

Hi,

I am trying to define a schema for a schema (that is, to implement
metamodel, model and model instance concepts) and i am stuck !
Do i need to redefine the W3C schema syntax or can i use my own
"vocabulary" that is name space and so on..

For instance, first I would like to define what a parameter is:
<parameterdefinition>
	<parameterdefinitionattribute name="parametername"/>
	<parameterdefinitionattribute name="parametertype"/>
</parameterdefinition>

Then, I would like to USE this parameter definition:
<systemparameters parametername="threshold" parametertype="integer"/>

And, eventually, I will instanciate it:
<threshold>12</threshold>

If you have some pointers that will be great.. ! I have already had a
look on RDF, but I don't think that will solve my problem.

Many thanks for your help !


jbg