i mean ER diagram, i want to develop .net version base on this DB

As mentioned before on some topic, you don't have to change or touch the database, instead use the builtin tools to add/change/retrieve the data.

Why exactly do you want a data flow diagram? In general, data is where you would expect it to be, according to the names of the tables in the ossn database. Basic user info is is ossn-users (underscore not dash) and most other data is related to site content is in ossn-entities-metadata and corresponds to entries in ossn-entities. The easiest way to understand how things work is just to examine it yourself in something ilke phpMyAdmin and see where stuff is based on what you see on your site.