Coding practices for DITA grammar files This section contains information about creating modular DTD- or RELAX NG-based grammar files. It explains how document-type shells, specialization modules, and element-configuration modules (constraint and expansion) are organized. File naming conventionsThe OASIS DITA Technical Committee uses certain conventions for the names of XML grammar files. We suggest using these conventions as a way to facilitate the interchange of grammar files.DTD coding requirementsThis section explains how to implement DTD-based document-type shells, specializations, and element-configuration modules (constraint and expansion).RELAX NG coding requirementsThis section explains how to implement RNG-based document-type shells, specializations, and element-configuration modules (constraints and expansions).