Is there a standardized way to get contents from other modules?

PostNuke had some functions called "hooks" that handled inter-modules requests for read/list/add/del/mod contents.
It was very easy to setup modules for newspaper-like section pages, advanced categories systems and so on.

I need to port some of those modules I wrote to Xoops... but I can't understand how should I do it...
I don't want to hardcode sql queries or call internal functions of the modules to keep a good layer of stability throughout versions...