Stumped by the DOM

Here's the deal: I'm using a DOM tree to store data of my app. Eventually I will add load and save code.

I've got a weird problem though. The DTD of my DOM contains this:

Code:

---

<!ENTITY % stdatt "id ID #REQUIRED title CDATA #REQUIRED">

<!ELEMENT data (topic?)>
<!ATTLIST data
xmlns CDATA #FIXED "http://www.cornedbee.com/jknowledger/storage/pure-memory">

<!ELEMENT topic (position, ((topic | content)*))>
<!ATTLIST topic %stdatt;>

---

I've tried three methods of creating the DOM Document, first only in memory via the DOMImplementation, second by "loading" a fixed string a passing a system identifier and third by loading an empty XML file:

Code:

---

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE data SYSTEM "../dtd/data.dtd">
<data xmlns="http://www.cornedbee.com/jknowledger/storage/pure-memory" />

---

Code:

---

try {
        DocumentBuilderFactory fac = DocumentBuilderFactory.newInstance();
        fac.setValidating(true);
        DocumentBuilder db = fac.newDocumentBuilder();
        doc = db.parse(new File("resources/PureMemInitial.xml"));

---

The parser is validating and doesn't give any errors.

Then I go ahead and create a root topic element:

Code:

---

Element docElem = doc.getDocumentElement();
Element root = doc.createElementNS(nmsp, "topic");
root.setAttribute("title", "Root");
root.setAttribute("id", ID.generate().toString());

---

I append this new element to the document element and let it rest.
I have also tried using a plain createElement without the namespace.

Later in the code I use getElementById to get the element. I KNOW that the id is correct, however the function always returns null.

I'm using a 1.4.2 JDK.

Does anyone have an idea why it doesn't work? It seems to me that id is not recognized as an ID, but I don't know why.

Thx in advance.