how to select elements with IDREF?

[Enric Jaen]

Hi,
 Could someone give me a clue about how to use the idref  attribute to select 
an element?

For example, in the following document:

<Company>
  <Departments>
    <Department id="d1">
      <Name>Enterprise Development</Name>
    </Department>
    <Department id="d2">
      <Name>Foundation Services</Name>
    </Department>
  </Departments>
  <Employees>
    <Employee DepartmentRef="d1">
      <Name>Jeff</Name>
    </Employee>
    <Employee DepartmentRef="d1">
      <Name>Mike</Name>
    </Employee>
   <Employee DepartmentRef="d2">
     <Name>Sam</Name>
   </Employee>
  </Employees>
</Company>

I'd like to obtain the Department name of Employee Jeff. How can this be done?

I guess I have to use the id() function, but I don't manage to solve this.

Any help will be appreciated.
Regards,
-Enric