CL-XML is a collection of Common LISP modules for data stream parsing and serialization according to the "Extensible Markup Language" and anscilliary standards. The modules perform parsing and serialization between XML, XML Query, and XML Path expressions and DOM-compatible CLOS instances. The XML processor includes a conformant, validating, namespace-aware model-based parser. It supports, in particular, namespace-aware DTD-based validation. The XPATH module comprises LISP bindings for the XML Path library, an S-expression-based namespace-aware path model, and a macro-based path model compiler which implements an XPATH-algebra. The XQUERY module comprises LISP bindings for the XML Query library, an S-expression-based query model which incorporates the XPATH facilities, and a macro-based query compiler. The base CLOS model implements the XML Query Data Model in a class hierarchy which presents an Infoset compatible programming interface.