SLAXML

SLAXML is a pure-Lua SAX-like streaming XML parser. It is more robust than many (simpler) pattern-based parsers that exist (such as http://phrogz.net/lua/AKLOMParser.lua), properly supporting code like <expr test="5 > 7" />, CDATA nodes, comments, namespaces, and processing instructions.

It is currently not a truly valid XML parser, however, as it allows certain XML that is syntactically-invalid (not well-formed) to be parsed without reporting an error.