Update 3.3.x i18n_base issue

[mvlcek]

Still don't get it. to modify the site map you just need to modify the urls and add new entries for languages.
What else does a plugin need to do to sitemap? Just making sure I understand.

Just some ideas:

e.g. other more detailed priority, other change frequency, additional URLs from custom fields or links in the content - I suppose search engines will scan links to PDF and probably other office documents, but you might add a special URL with e.g. an indexable PDF-version of a CAD file?

The I18N plugin uses multiple files and encodes the language in the URL. You could also add additional title and content fields in the page XML (e.g. <content lang="de">) and then would need to read the page file to know that this page file is in reality two language pages.

If you have a frontend user type plugin, you might have a field access=public/base member/gold member and want to include only the public pages in the site map.
Or you could include the base member pages in the sitemap and serve them (or a garbled version e.g. all sentences in random order) to specific search engines (so it is indexed) and then display a "Please become a member" page to visitors.