[TYPO3-mvc] Libraries in Extbase

[Christian Lerrahn (Cerebrum)]

Hi,
this is more of a DDD question than really an Extbase one. It might
even be more of a philosophical question than a technical one. However,
I've decided to ask it here and hope for someone to point me to a
better place if there should be one.

Traditional extensions can be written as libraries. That can be very
useful if functionality gets re-used in extensions a lot. I suppose, so
far this will work with Extbase, too. However, I am wondering how a
library should be designed. It still has a clear model but where does
the API go? I would argue that the API is the user interaction part and
therefore the controller. Or does a library have a minimal controller
and the API is provided as the domain?

Is there any standard for how a DD library is set up? Or maybe a
consensus on that for Extbase/FLOW3 at least?

Cheers,
Christian