I have a requirement to build one parent site and few child sites..using domain and sub-domain concept and want to have installations of joomla at parent and all sub-domains. But I want only my parent site to hold user data and Alpha user points data while my child sites would be hosting components and modules separately and use user data and Alpha user points data from parent site.

Could any one suggest me is it a good Architecture to go and is there any extension or component already available to achieve it. Example
below:

parent site movies.com Child sites braveheart.movies.com, troy.movies.com

I will have forums, blogs and other component installations at braveheart and troy sub-domains seperately while my Alpha user points and users db/tables would reside at movies.com(main domain).

It's like single-sign on or Centralised Alhpa user points, but free to install same component and modules at different sub-domains.

Highly appreciate any replies or solutions proposed

The concept of JMS is based on the sharing
- Sharing of the same joomla application (php code)
- Sharing of the content of a limited number of extensions.

So in terms of sharing of the users and alpha user points, this mean sharing the MySQL tables used by the Joomla users and this extension.
See the list of extension that can have their content shared.
www.jms2win.com/en/list-of-extensions?vi...id=269&Itemid=53

As you share the PHP code between all the websites, it is required that all the extensions used by the slave sites are installed in the master (to have the PHP code).

When you create a slave site, you can use a JMS template rule that contain the default content for the slave site. So you can have the pre-installed extensions required for the slaves derived from your template website.

Concerning the Single Sign-In, you mentioned all the websites as "subdomains" of a unique domain name (movies.com).
So you can use the Joomla 2.5 (or higher) Global Configuration - cookie domain field to put the ".movies.com" as the domain that must share the session info.
So that apache will know that this domain can share the session info with all the subdomains of this domain. (Only this domain will be able to login).