Peter,<br><br>To me, the choice of zxx vs und depends on your goal in the particular case.<br><ol><li>If the goal is to have a category for a pure 'code',non-linguistic like an ISO script code or other tags or codes that are intended to be used internal to programs, then 'zxx' would be appropriate.</li>
<li>If the goal is to have a category for a 'name' that is linguistic, but meant to be some sort of neutral 'fallback' that is comprehensible by people coming from a wide variety of linguistic backgrounds, then 'und' would be appropriate.</li>
</ol>Mark<br>