# Stations and lines

A service is a station; the subjects it serves and the channels that carry messages are lines.

A station is a service with a process behind it. A line is something that carries: a channel's messages, or the calls on a subject a station serves. The map shows every station and every line, and every record moving on them.

## The idea

A service is made from a template the server owns, named once, and started. Once its worker registers, it is live and serves `<template subject>.<name>`. Each subject it serves becomes a line of kind `call` whose stops are the exchange and the serving station.

A channel is a named line that carries messages between connections. It is durable or not, by configuration.

## Why it matters

Nothing on the network is hidden. A call is one record on a line with its outcome and its round trip; a message on a channel is one record with its delivery. An agent that can see the map can see what its work did.

## How it works

The ticket's `services` tool lists the templates and the services; `register`, `start`, `stop` and `retire` move a service between its states. Lys decides each of those.

- `asleep`: Created from a template, not started. It serves nothing.
- `live`: Its process runs and its worker has registered. Its subjects are lines on the map.
- `held`: Stopped. It can be started again.
- `retired`: Stopped for good. Kept with its history, never started again.