"Core" seems to cover over a multitude of things, encompassing all the modules that ship with the Drupal code base. But there seem to be levels of "core"-ness, and I'm wondering if there is official terminology to distinguish between these. For example:
- There is the code that is not part of any module. Does "core" include this officially? It's not clear to me.
- There are required modules: without these (at least in Drupal 7) you can't really build a Drupal site.
- There are all the default modules that are part of Core. You can turn many of these off without a problem, but they're still considered "core".
- There are modules that are turned off by default (PHP Filter) and which may even be considered a bad practice to use under normal circumstances (PHP Filter, again).
If I were naming these levels, I might call them
- The Drupal Kernel
- Deep Core Modules
- (Normal) Core Modules ("Core Modules" would include 2 and 4 as well)
- Outer Core Modules
But it seems like Dries may have an official terminology already. Is there such a thing?