a question of DOMSource

Hi:

When I using Xalan 2.7.1 to transform a DOM Source;

I find that:The Node combine with DOMSource must be a Document and It cannot
be just a Element; 

Does anyone know if this limit is correctly or wrong, and why?

 

Following is a simple program to illustrate it

 

Document doc = DocumentBuilder.parse(.)

 

//if I using document as input, the result is correct;

Transformer.transform(new DOMSource(doc), streamResult);

 

//but if I using element as input, the result is wrong;

Transformer.transform(new DOMSource(doc.getDocumentElement), streamResult);

 

 

Ps: xml  xslt I used:

Xml:

 

<?xml version="1.0" encoding="UTF-8"?>

<Record xmlns="http://www.tongtech.com/tiwen/record1">

<content1>a</content1>

<content2>b</content2>

<content3>c</content3>

</Record>

 

Xslt:

It's too long, but it logical is very simple, just exchange field content2 &
content 3; 

And I am sure it's correctly, because I have use a StreamSource(xml-stream),
and Document 's DOMSource as input, their result both are correctly;

but if anyone interest with it, I can post it in reply;