The XML version was prepared using an sgmlspl/SGMLS.pm script, with some knowledge of the article document type, that converts LaTeX-like positional arguments and options to the corresponding named elements. The HTML and LaTeX translations were made from the XML version using other sgmlspl/SGMLS.pm scripts. These scripts may be found in the GELLMU distribution.
XML files made this way can be validated as SGML, and now there is a document type definition suitable for an XML parser. The SGML validation is somewhat more thorough than the corresponding XML validation since there are a few things that can be modeled under the didactic GELLMU SGML Document Type Definition that cannot be modeled under the corresponding XML document type definition.
On the other hand, there is a form of enrichment in the XML made this way since the translator writes individual names based on the names of their parent elements for the LaTeX-like positional arguments and options rather than the generic names ag0 (for an argument) and op0 (for an option), and the translator writes end tags for all "container" elements when these end tags are not necessary for the author and are redundant in the eye of an SGML parser.
Whereas the GELLMU Syntactic Translator, the program which converts GELLMU source to SGML, has knowledge only of syntax with essentially no understanding of GELLMU command names, the program that translates the SGML to XML has some, though not full, knowledge of command names.