[om] OpenMath SigFile JAVA class problem

[olga caprotti]

Hi -

I am trying to write a JAVA class that uses
DOM to read the XML Signature files and has
methods to return the OpenMath Objects that
represent the signatures. So far I get errors
like:

com.sun.xml.tree.DomEx: This node isn't allowed there.
        at com.sun.xml.tree.DomEx.<init>(Compiled Code)
        at com.sun.xml.tree.XmlDocument.checkChildType(Compiled Code)
        at com.sun.xml.tree.ParentNode.appendChild(Compiled Code)
        at com.sun.xml.tree.XmlDocument.appendChild(Compiled Code)
        at
nl.tue.win.riaca.openmath.lang.SignatureFile.getXmlSigObject(Compiled
Code)
        at
nl.tue.win.riaca.openmath.lang.SignatureFile.getSigObject(Compiled Code)
        at nl.tue.win.riaca.openmath.lang.SignatureFile.main(Compiled
Code)


produced by the code:

    public String getXmlSigObject(Node node){
	
	String nodename = node.getNodeName();
	String sigobj = null;
	
	if ( nodename.equals("Signature") )
		{
		    
		    Node child =   node.getFirstChild().cloneNode(true); 
		    if ( child != null )
			System.out.println("Child is" + child.getNodeName());
		    XmlDocument document = new XmlDocument();
                    // we try and fix the doctype until we know better
		    DocumentType  doctype = document.setDoctype(null,
			"http://www.riaca.win.tue.nl/~olga/openmath/dtd/omobj.dtd",null );
		    StringWriter writer = new StringWriter();
		    document.changeNodeOwner(child);
		    document.appendChild(child);
		    try{
			document.write(writer);
			sigobj=writer.toString();
		    }
		    catch (IOException e){
			sigobj = null;
		    }
		}
	return sigobj;
    }

Anyone has XML-DOM experience in JAVA? 
Have you ever encountered this problem?

Thank you
olga

--
Olga Caprotti        <olga at win.tue.nl> 
URL        http://www.win.tue.nl/~olga
Tech. Univ. Eindhoven,     P.O.Box 513
5600MB Eindhoven     (The Netherlands)
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