Thin and Fat Client Model

There are two type models of the client-server architecture.

Thin-client model
In a thin-client model, all of the application processing and data management is carried out on the server. The client is simply responsible for running the presentation software.

Fat-client model
In this model, the server is only responsible for data management. The software on the client implements the application logic and the interactions with the system user.



Thin CLient Model:
-Used when legacy systems are migrated to client server architectures.
-The legacy system acts as a server in its own right with a graphical interface implemented on a client.
-A major disadvantage is that it places a heavy processing load on both the server and the network.

Fat Client Model:

-More processing is delegated to the client as the application processing is locally executed.
-Most suitable for new C/S systems where the capabilities of the client system are known in advance.
-More complex than a thin client model especially for management. New versions of the application have to be installed on all clients.

Activity Diagram

Activity diagrams are used for to show a subprocess of a system by figures. Big black dot means the start and the Black dot and a circle outside it means end. Also the arrows represent yes and no answer to the process.That means if yes process done if no can not be done. The diamond are the process steps.
We still continue on the example we examined at last two articles. Here are the some examples from the dynamic web site system:

Activity diagram for use case of Adminstrator to send and receive mails.



Activity diagram for use case of all users to post messages.



Activity diagram for use case of Student to add comments.

Use Case Diagram

Use case diagrams are known as the information about whole system with drawn syntax.The article just before that i have talked about a system: a dynamic web site system the use case diaram below belongs to the same example.

Also some explanations about the diagram as:

Use Case UC1 : Upload&Download Process
Primary Actor : Administrator
Steakholders & Interests:

1. Administrator : Wants all rights to manage the site in minimal time and effort. Also their need is to achieve the site to manage it from every computer they want which by they can access to the Internet.
2. Student : Wants reach to the documentations that he/she needs to download, and add comments to the annocuments also posting messages to the admins. These process needed to be done in a small time period.
3. Invited Speaker : Wants the rights for to add the documantations for their class in minimal effort.To get these rights they need to enter the web site by their user names and mail adresses that they reported to the admins before.
4. Guest : Just can read the page and post messages. Also become a member of the site with his/her student number.

Preconditions : Administrator has logged in to the site by using their username and password.
Success Guarantee (Postconditions) : Text is uploaded succesfully. Web site updated.


Main Success Scenario:

1. Administrator opens his/her control panel.
2. Administartor writes down the address of the document that he/she want to upload.
3. Database stores the document file.
4. Student/Invited Speaker /Guest reads the document from website.
5. Student & Invited Speaker downloads the document.
6. Administrator delete the document link from website.

Extensions:

At any time system fails:
3.a. Database can not stores the file.
3.b. Wrong document file’s address entry by Administrator.
5. Student & Invited Speaker can not dowload the file since the system errors.

For next article the activity diagram of the same example will be axplained.