# The map

> What a Flozu map holds, from parts and lines to zones, notes, views, stories and scenarios, and the rules that keep it consistent.

Everything you draw is one **map**. One document holds it all, and the canvas, the scenarios, the stories and presenting all read from it.

| Thing      | What it is                                                                                                                                           |
| ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
| Part       | A piece of the system, of one of 28 kinds, with an optional technology and a flag for parts someone else runs.                                       |
| Line       | A connection between two parts. It carries requests or messages, forward or both ways, with a label, a protocol and a rate.                          |
| Zone       | A frame around parts that belong together: a region, network, system, team or any other zone. Zones nest.                                            |
| Note       | Plain words on the canvas, for whoever reads the map later.                                                                                          |
| View       | One way of showing the map to one audience. See [views](https://docs.flozu.app/concepts/views.md).                                                   |
| Story      | A walk through the map for presenting it. See [stories](https://docs.flozu.app/guides/stories.md).                                                   |
| Scenario   | A saved “what if?”, such as Black Friday. See [scenarios](https://docs.flozu.app/guides/scenarios.md).                                               |
| Map inside | Another map a part opens into, such as a payment service’s own modules. See [maps inside parts](https://docs.flozu.app/guides/maps-inside-parts.md). |

## Numbers: rates and limits

A map holds the numbers behind its motion. **Traffic lives on lines,** as a rate: how much each carries each second at the busiest moment of a normal day. **Limits live on parts,** because a limit belongs to the part that enforces it: a capacity, a limit that turns traffic away, or a buffer that holds what’s waiting. See [traffic and limits](https://docs.flozu.app/guides/traffic-and-limits.md).

## What the map keeps true

Flozu checks a map after every change and every time it opens one, so a map can never be broken:

- Every id is unique across the whole map, so anything can be found by its id alone.
- A line joins two different parts that exist.
- A zone a part, note or other zone belongs to exists, and no zone is inside itself.
- Views, stories and scenarios only mention things that exist, and a map always has at least one view.
- Positions are on the canvas as a whole, even inside zones.

When you delete something, Flozu tidies up after it in the same step: deleting a part removes its lines and every mention of it in views and stories; deleting a zone keeps what was inside, in the zone around it.

## Looks never change meaning

A part’s kind says what it does: how traffic moves through it and which limits it can have. How it looks (its card, drawing, size and colours) is separate, so a part can look however suits the map without changing how it behaves.

## Saved as one file

A map saves as one `.flozu.json` file. See [file format](https://docs.flozu.app/reference/file-format.md).