Next Generation Schema/Advanced Relationships Table Structure
The main table is link. It contains the begin and end date info, and the link_type foreign key field that specifies what kind of AR it is. It also has a count of how many other attributes that particular link has in the attributecount field.
There are tables for every possible combination of primary entities (artist, label, recording, release, release_group, url, work), all prefixed with l_ and all with the same format. Four of them are shown in the diagram above. They contain a flag, modpending that marks if there are pending changes to the AR, and three foreign keys: link that points back to the associated entry in the link table, and entity0 and entity1 that point to the associated entry in the corresponding primary entity table (i.e. artist, recording, url, etc.).