Nima:
OpenACS has a huge amount of documentation. All APIs are documented at https://openacs.org/api-doc/ and the same URL within any installation.
Consistent APIs are an ongoing challange, so we are working on it.
"As a newbie I find it extremely hard to understand how I can define objects in OpenACS." This I find very hard to believe. Besides the huge amount of existing example code there is the tutorial: https://openacs.org/doc/openacs-5-1/tutorial-database.html and the lower-level, but extremely detailed https://openacs.org/doc/openacs-5-1/object-system-design.html
Please if you are looking for answers to a question, and can't find it in the documentation, please ask on the forums. If it is hard to find something, please let us know. Anyone who can help out with documentation is welcome to.
While on the subject of documentation one place I think we need to streamline the existing documentation is on the install. It has been said that the install documentation shows how to build a production ready environment. That should be a seperate advanced document. A goal should be to have a one page install document that gets a minimum system running. With many links to more advanced topics.
