Help: XML Schema - any element with fixed type?

[Risheng Lin <rlin@eng.utoledo.edu>]

Hi,

Can any one tell me whether there is a way to design an xml schema such 
that it allows a user to define any kind of element but with fixed types? 
i.e. the element tag name can be freely chosen by the user as long as the 
user's data follows the type defined in xml schema?

For example:

I want the following xml to be validated:

<data1>
      <x />
      <y />
</data1>


<data2>
       <x/>
       <y/>
  <data2>

Here <x/> <y/ > are the datatype defined in xml schema and it needs to be 
fixed - this can be easily defined in XML schema; but I want the data tag ( 
here: data1 and data2 ) to be freely chosen by user and the document is 
still valid. How to design such schema?

Note: it is different from <any>, and <anytype>.

Any one can show my how to do it?

Thanks in advance.

Risheng