Web Client-Server Interaction

Normal (Static) Document Retrieval

+---------+ (1)Request    +--------+           +--------+
|         |-------------->|        |           | Server |
|   Web   |               |  Web   |-----------|  File  |
| Browser |               | Server |(2)Retrieve| System |
|         |<--------------|        |           +--------+
+---------+  (3)Reply     +--------+

Dynamic Document Creation

+---------+ (1)Request    +--------+ (2)Input  +---------+
|         |-------------->|        |---------->|         |
|   Web   |               |  Web   |           | A "CGI" |
| Browser |               | Server |           | Program |
|         |<--------------|        |<----------|         |
+---------+  (4)Reply     +--------+ (3)Output +---------+
                                                    |
                                                    |
                                                +--------+
                                                | Server |
                                                |  File  |
                                                | System |
                                                +--------+

Document and Service Delivery Combined

+---------+ (1)Request    +--------+ (2)Input  +---------+
|         |-------------->|        |---------->|         |
|   Web   |               |  Web   |           | A "CGI" |
| Browser |               | Server |           | Program |
|         |<--------------|        |<----------|         |
+---------+  (4)Reply     +--------+ (3)Output +---------+
                              |                     |
                              |         +--------+  |
                              |         | Server |  |
                              +---------|  File  |--+
                          (2,3)Retrieve | System |
                                        +--------+