Unified Modeling Language (UML) is a standard way to visualize the design of a system.
The previous page was about the design/look from the user perspective, and now we are talking about the design of the implementation (the code).
You may need a simple tool to help on drawing the graphs. (Of course you can use pen and paper if you don't want to co-work the graph online with others.)
"Domain model" by Kishorekumar 62 - Own work. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Domain_model.png#/media/File:Domain_model.png
- No detail of implementation
- Domains (players) who involve your project
System Sequence Diagram
This is an important diagram. Most of time, we "talk" about the flow we want, but drawing it down became helpful in making it happen. Also, as we "see" the flow, more ideas can be inspired, and bugs can be found easily.
Object Model Diagram
It's pretty close to the real code. In Object Model Diagram, we can see all the attributes and functions of objects.