Are XML Tags starting with '_' underscore valid with XML DB?

Question

Dear Experts,
I am importing an XML data file into an XMLType field in a table, then extracting data within a tag. I am using Oracle Database version 10.2.0.2.0
The data file I am using looks like:
<?xml version="1.0" ?>
<_PARENT>
<_EXAMPLES>
<_ITEM_NO>1</_ITEM_NO>
<_PAX_NO>1</_PAX_NO>
....etc.
If I then extract it using the command:
SELECT extractValue(e.XML_INVOICE_DATA, '/_PARENT/_EXAMPLES/_ITEM_NO')      
FROM XXIBO_XML_STAGE_TABLE      e
I get the error:
SQL Error: ORA-31011: XML parsing failed
ORA-19202: Error occurred in XML processing
LPX-00601: Invalid token in: '/_PARENT/_EXAMPLES/_ITEM_NO'
31011. 00000 - "XML parsing failed"
*Cause:    XML parser returned an error while trying to parse the document.
*Action:   Check if the document to be parsed is valid.
If I take out the '_' underscores prefixing the XML tab names e.g:
<?xml version="1.0" ?>
<PARENT>
<EXAMPLES>
<ITEM_NO>1</ITEM_NO>
<PAX_NO>1</PAX_NO>
....etc.
and run:
SELECT extractValue(e.XML_INVOICE_DATA, '/PARENT/EXAMPLES/ITEM_NO')
FROM XXIBO_XML_STAGE_TABLE      e
This query works, which leads me to my origional question - is it invalid to have XML tags that are named starting with an underscore, when manipulating it in an XMLType object?
Many thanks for your time,
Mark

Answer 1

Ants - thanks very much for that, has been useful.
Mark