I've played with Composite C1 for many hours, from the sample of Compostie C1 site and help pdf, I only see it can develop the static website.
My question is can it used to develop data based website, is there a component like Login module, datalist module, user access control module, how it handles data from server, does it use ORM, etc? I expect using C1 to develop a little bit complicated website with user interactions. Can it do this job? If can, any documentation? Thanks.
You can pretty much develop sites of any complexity with Composite C1, as it works perfectly together with ASP.NET user controls, Master pages and MVC.
For developer documentation, see http://docs.composite.net/
We are currently developing multiple complex solutions on Composite C1, so if you have knowledge in ASP.NET this should be no problem.
Even though C1 has many modules and allows to build quite complex sites, you will hit a limit of complexity of course when you try to build a site without any coding on your own, just with the CMS capabilities.
But there are also some prebuilt packages for some things that you asked for like the commercial Extranet package for access control and user management.
Also have a look at the other modules.