[jdom-interest] . is not allowed in XML names?

[Bob_Lee at averydennison.com]

I've run across the following exception:

org.xml.sax.SAXException: The name "Foo.bar" is not legal for JDOM/XML elements:
. is not allowed in XML names..

Since when?  Both Harold's "XML Bible" and Eckstein's "XML Pocket Reference" say
that periods are legal characters in element names.  Is this a JDOM-induced
limitation, or has XML changed since those books were written?

     -Bob Lee