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77In this lesson we're going to look at subscriptions. Subscriptions are probably
88the most complicated part of writing agents, so there's a fair bit to cover.
9+Before we get into the nitty-gritty details, we'll give a brief overview of
10+Gall's subscription mechanics.
11+
12+The basic unit of subscriptions is the _path_. An agent will define a number of
13+subscription paths in its `on-watch` arm, and other agents (local or remote) can
14+subscribe to those paths. The agent will then send out updates called `%fact`s
15+on one or more of its paths, and _all_ subscribers of those paths will receive
16+them. An agent cannot send out updates to specific subscribers, it can only
17+target its paths. An agent can kick subscribers from its paths, and subscribers
18+can unsubscribe from any paths.
19+
20+The subscription paths an agent defines can be simple and fixed like
21+`/foo/bar/baz`. They can also be dynamic, taking data of a particular atom aura
22+encoded in certain elements of the path, and then decoding it to an atom of that
23+aura. These paths can therefore be as simple or complex as you need for your
24+particular application.
925
1026## Incoming subscriptions
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