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@@ -40,3 +40,53 @@ Its genesis node records the first users, with the swarm ID, in its first change
 
 A swarm nobody could manage doesn't start: with none of them with `["_continuum"]`,
 `--genesis` is refused, naming both options.
+
+## At the HTTP API
+
+Every request is checked against the registry, as the node serving it holds it: a
+change to it counts on a node as soon as it has reached it.
+
+* **The store** (`/store`, `/stream`): writing a path (`PUT`, `POST`, `DELETE`) takes
+  `write` on it; `?prune=true` deletes maps left empty only up to the highest one the
+  user may write. Reading takes `read`: of a place the user may read only partly, it
+  sees the keys on the way to what it may read, as a directory one may pass through
+  but not list (a capability on `servers/eu` shows `servers` with `eu` alone in it),
+  and nothing else; a list on the way is left out whole, as its items have no paths of
+  their own. Native forms (`text/plain` of a map, a counter as its own type) only of
+  what it may read whole. What a write answers with is what was written. A stream
+  shows what the user could read when it opened.
+* **Protocol data** is in the store too, under `_continuum`: `read` and `write` on it
+  as on any path.
+* **Looking at the node** (`/admin/stats`, `GET /peers`, the dashboard): any user with
+  a capability.
+* **Remakes** (`/admin/remakes`): `read` on `_continuum/remakes` to look, `write` to
+  propose or abort one. **Forgetting a peer** (`DELETE /peers/…`): `write` on
+  `_continuum/forgotten`.
+* **Everything else an operator does** (`/admin/config`, `/admin/log`,
+  `/admin/document`, `/admin/changes`, `/admin/epochs`, `/admin/quarantine`, `/debug`):
+  `read` on `_continuum` to look, `write` on it to act.
+
+A user the node lets in but the registry doesn't have may do nothing (`403`).
+
+`[]` and `["_continuum"]` are two capabilities on purpose: protocol data acts on the
+whole swarm (its members, its remakes, its users), so it is given apart, never by
+accident with the data. A user who may do both has both.
+
+## An existing swarm
+
+A swarm whose document has no registry (one from before it, `_continuum/users`
+missing) goes on as before: every user a node lets in may read and write the swarm's
+data and use the admin endpoints, and only those in `--protocol-writers` write
+protocol data. It gets a registry once a protocol writer writes one, through the store:
+
+```sh
+curl -u alice --request PUT --header 'Content-Type: application/json' \
+  --data '{"since": 0, "by": "user:alice", "disabled": false,
+           "caps": {"1": {"path": [], "rights": ["read", "write"]},
+                    "2": {"path": ["_continuum"], "rights": ["read", "write"]}}}' \
+  http://localhost:3000/store/_continuum/users/alice
+```
+
+From that write on, every node serves only the users the registry has, so the first
+entry must be the writer's own, with `["_continuum"]`, or nobody may change the
+registry again; add the other users the same way.