DocBook is a schema. It is particularly well-suited to books and papers
about computer hardware and software (though it is not limited to these
applications at all).
The version is a complete rewrite of DocBook in RELAX NG.
The intent of this rewrite is to produce a schema that is true to the
spirit of DocBook while simultaneously removing inconsistencies that
have arisen as a natural consequence of DocBook's long, slow evolution.