[Sharlikran]

Let's say for Quest Map it has an optional dependency for a text box. So when you type a slash command a list of hidden quests appears in the text box. If the author made that optional then when you load the mod the game checks both required and optional libraries. If you are missing the requirements then the mod doesn't load. If you are missing the optional dependency then the mod will load anyway because the author checks to see if the dependency is loaded before using it. Authors have to specify the optional dependency in a special text file to ensure that the game loads the optional dependency prior to the mod.