How to represent the flow of a real-time web application

Question

I am writing my thesis and need to represent the process flow of my application. I need to have a diagram that represents the flow of each process in my application. How do I represent an application which is meant to be "real-time". I have a shared whiteboard where whatever a user draw/write is reflected on the whiteboard of the other participants in the same room. For example if a user draw a rectangle, the coordinates and stuff will be sent to the other users for the rectangle to appear on their whiteboard. At the same time, the coordinates are stored in the database.

Answer 1

Well, there are obviously many solutions, but a sequence diagram can show what you need. Assuming you have two representation boards and a central instance then a change on the first board will be communicated to the central instance. This broadcasts the change to all connected other boards which in turn show the change.

Of course there are a zillion different ways to implement the scenario. But with a seuqence diagram the involved communication can be shown best.

Below picture shows an example how this can look like:

You will need to draw quite a number of those to show how the concurrent board drawings are communicated.