Drupal 7: Node translation
Gábor Hojtsy erklärt in Teil 4 der Serie Drupal new multilingual systems sehr ausführlich wie Node Translation in Drupal 7 funktioniert.
The built-in translation module forms translation sets of nodes, where each set has a base node that is translated to the other languages. So the general idea is that you submit nodes in the source language first and translations come afterwards. Translation set relations are very simply managed in the database, but I have not yet seen contributed modules to expose advanced editing of this data (such as assigning existing nodes to existing translation sets, or switching to a different base node for the translation set). It should be fairly easy to write such a module though. In summary, the general concept is that translation sets are formed on top of nodes.