Before we can start creating diagrams, we need a scheme that guides what we diagram, and how — e.g. what set of diagrams do we need, how do they fit together, and what should be included in each one — and what should be left out.
Such a scheme also needs to define a specific set of concepts that will be employed to describe the subjects.
FC4 uses The C4 Model, created by Simon Brown, as its foundation; it is fundamentally a tool for authoring C4 diagrams.
The C4 Model website has very detailed definitions, explanations, and examples; it is the canonical definition of the model. We’ll continue to summarize it here for convenience, but any errors or ommissions here are our own and the information on the website takes precedence.
In a nutshell, the C4 Model defines two sets of diagrams: the core set and a supplementary set. FC4 currently supports two of those core diagrams and two of those supplementary diagrams.
The diagrams build on each other, with each successive diagram “zooming in” to a specific element in the prior diagram.
They are, from the highest level (most zoomed out) to the lowest level (most zoomed in):
| Type | C4 Category | Description |
|---|---|---|
| System Landscape | supplementary | “…a high-level map of the software systems at the enterprise level…” Not focused on any specific system; shows the overall landscape of systems within the business. This is the highest possible “zoom level”. |
| Context | core | Focuses on a specific system, showing it as a box in the centre, surrounded by its users and the other systems that it interacts with. |
| Container | core | Shows the separately deployable units that make up a system, the technologies they employ, and how they interact. A “container” is something like a web application, desktop application, mobile app, database, file system, etc. |
| Dynamic | supplementary | “…show[s] how elements in a static model collaborate at runtime to implement a user story, use case, feature, etc.” Seems promising for illustrating workflow or dataflow diagrams. |
For the full definitions please see Core Diagrams and Supplementary Diagrams.
Anyone using FC4 is of course free to use or not use whichever diagrams they see fit.
Please continue to The Textual Notation or go back to the top page of the manual.