Architecture:MediaWiki/library layer

The library layer consists of all standalone libraries used. Code in the libraries has no knowledge of the application, and the individual libraries generally have no knowledge of each other.

The library layer resides at the bottom of the stack, since all other layers may make use of libraries.

Status:
As per August 2020, the idea of a library layer is well-established, with several components in the includes/libs directory waiting to be extracted into standalone libraries.

Constraints:
Code in libraries must not have any knowledge about the application.

Example:
Examples of libraries used by MediaWiki include pear/mail and wikimedia/purtle.