[ovirt-devel] Cluster version - where is it defined?

Hello, I'm trying to understand where the Cluster Compatibility version is defined and which commands are supported in each version. I'm inspecting the ovirt-engine, libvirt, and vdsm source code, but I imagine there is any paper or webpage where it is defined. At least a list with features or commands, something like this. I searched this list and found pretty old messages, but no clue on this topic. Regards, Marcos