A recent repair of a WP database is an opportunity to explain relationships in taxonomies used by xili-language since WP 2.3.
What see the webmaster ?
In xili-language settings a language has disappeared but not in posts list.
When checking the database, the term of language is present and also the relationships with taxonomy ‘language’. But languages are grouped inside a group named ‘languages_group’ and a line of relationships table has a defect (object_id with 0 instead of term_id of the language line in terms table.
The 3 tables and links between the three tables to show how terms (languages) from taxonomy ‘language’ are grouped in taxonomy ‘languages_group’. (The circle show the id changed by database error to 0 – so hidden in settings)
In this diagram, relations between languages and posts are not presented – they are similar to category or post_tag taxonomies. You can see at right the count of posts of each languages in terms table.