SSAX is a package of low-to-high level lexing and parsing procedures that can be combined to yield a SAX, DOM, validating parsers, or a parser intended for a particular document type. The procedures in the package can be used separately to tokenize or parse various pieces of XML documents. The package supports XML Namespaces, character, internal and external parsed entities, xml:space, attribute value normalization, processing instructions and CDATA sections. This package is intended to be a framework, a set of "Lego blocks" you can use to build a parser that follows DOM, SAX or other discipline and performs validation to any degree. As an example of the parser construction, the package includes a semi-validating SXML parser.
Related to SSAX are SXPath queries and SXML transformations.
Main SSAX/SXML page
http://pobox.com/~oleg/ftp/Scheme/xml.html