In 0.9, the API only parses web.xml files that have 2.2 and 2.3 information. Version 2.4 files are more problematic, because the headers have been changed to use an XSD rather than a DTD.
Additionally throughout the code, when a file is parsed, we just 'guess' that it's a 2.3 web xml, without actually checking - this isn't good, as 2.2 doesn't allow filters, and 2.4 has a different layout for taglibs.
The change to an XSD means that nodes in a 2.3 will be different from nodes in a 2.4 web.xml - the latter will be in a different namespace. Need to keep the main API as easy as possible to prevent having to 'know' which version you're adjusting. This can be done by extending the tag type metadata to include the Namespace information.