Main Releases shall use the ResourceGroup hierarchy depicted in Figure 1.
In addition the following rules shall be applied:
- Main Releases should have the IsMainRelease flag set to True.
- Track bundle resource groups should be sequenced.
- All Primary Resources should be sequenced in the context of their track bundle ResourceGroup (i.e. the sequence restarts with the next track bundle).
- Secondary Resources (e.g. cover images) content items shall not be sequenced.
- For each Resource, at least one Release Date (i.e. either original and/or global and/or territorial) shall be provided;
- For each Resource, the sender shall province any IndirectSoundRecordingID. IndirectVideoID or IndirectMidiId, identifying the MusicalWork (preferably an ISWC) used, that it has reasonable access to; and
- Resources Level Attributes held at the ResourceGroupContentItem level to qualify the use of a Resource on a Release include:
- Bonus Tracks and
- Hidden Tracks.
Figure 1 — Release Structures: Main Releases
Please note, that ResourceGroups are also used to represent multi-part musical works in Classical Audio Albums (see also Clause 5.2.5).
This Clause does not apply to Film Bundles and TV Series Releases.
 In older versions of the Release Notification Message Suite Standard, where the IsMainRelease flag is not available, the same functionality can be achieved by (i) placing the main Release as the first Release into the ReleaseList composite and using a ReleaseReference of “R0”.