Basic XML question: Purpose of a DTD?

Question

What does a DTD do? And do I need one? I've been using an XML config file for my app, but now that I'm looking for a simple XML editor, I can't just open my .xml file in the editor and GO. I need to specify some kind of DTD as well, so I can't even edit my file as I do in Forte.
Thanks

Answer 1

I read the SUN tutorials on using the DOM parser. I chose to use the DOM parser instead of the SAX parser, because it is simple to load a file and let the API parse the xml file from you. Then all you need to do is call the various methods that are provided to access parts of your XML file.
For example, here is the function I use to load my config file, which I grabbed from the examples in the SUN XML tutorial. See part III of:
http://java.sun.com/xml/jaxp/dist/1.1/docs/tutorial/index.html
public boolean loadFile(String filename) {
     // Get an instance of a DocumentBuilderFactor
        DocumentBuilderFactory  factory = DocumentBuilderFactory.newInstance();
     try {
            // Have the factory create a document builder
            DocumentBuilder builder = factory.newDocumentBuilder();
            // Builder parses the XML file and save it into a document object.
            xmlFile = builder.parse( filename );
            return true;
     catch (SAXException sxe) {
            // Error generated during parsing.
            Exception  x = sxe;
            if (sxe.getException() != null) x = sxe.getException();
            x.printStackTrace();
            return false;
     catch (ParserConfigurationException pce) {
            // Parser with specified options can't be built.
            pce.printStackTrace();
          catch (IOException ioe) {
           // I/O error
        System.out.println("XMLEasyReader: Error opening the config file : " + filename);
           ioe.printStackTrace();
     return false;
    }