Which UML diagram to use PLZ HELP

i am creating a cms for community web sites. there is the admin section, user section and a lot of features.
i am now trying to create a design document n i thought of drawing sequence diagrams for it. bt the problem is, i dont understand for which processes should i do it as there are so many things that an admin or a user can choose to do like:
admin can-> create more admins, edit site, edit features, change user/feature privileges,… etc
user can-> login, edit profile, send/read/edit/delete messages, images, communities and the same with a lot of other features.
so i am not sure how to represent all this.

which uml diagram should i use to best fit my need?? :oops:

It is difficult just use one type of diagram to show all you need.
Use case diagrams are good at the begining, you can start with them.
You can define all your user scenarios, all functions like login, send read, … with them.

I hope it helps. If you have any other questions just ask.


Thanx pall, :stuck_out_tongue:

ill start with the use cases then. if i come across any more dificulties ill definitely ask u.