Please note that these diagrams may appear primitive and simplistic. This is by design.
This is what ensures all parties involved can easily understand the structure and objectives of the system.
DOMAIN MODEL
A Domain Model is a diagram which depicts the main entities of the system. It illustrates the relationships between those entities and indicates what data (which fields) we are storing or processing in the system for each.
An example Domain Model
In some cases, if the entities contain many fields, the fields are not listed in the diagram to save space and are instead listed in a separate document in table format for each entity.
USE CASE DIAGRAM
A Use Case Diagram is used to depict which users are expected to interact with the system, and which activities they should be able to perform by using said system. This is a very good way to summarize the overall functionality of the system and confirm that all the objectives we need to reach can be reached.
An example Use Case Diagram
FLOWCHARTS
Every system's non-trivial process requires proper documentation, and flowcharts are a perfect way to indicate how the system should behave when performing certain operations, or how it should respond to user input and different sets of circumstances. Flowcharts are easy to understand and convey very clearly the different decisional flows that may occur with the system.
An example Flowchart
USER INTERFACE (UI) MOCK-UPS
It is important to define, on a visual level, how the system will look and feel. The user interface can make or break the experience, and by devising mock-ups, we are ensuring a quality experience for the end user, and streamlining the development process by making upfront decisions about the general layout of the system.
An example User Interface (UI) Mock-Up