# Specifying Selectors

Specify message selectors for global topics as properties of routes. You can define these properties in two ways:

- Define selectors when creating the route (either in routes.conf, or with the administrator command `create route`).
- Manipulate selectors on an existing route (using the `addprop`, `setprop`, or `removeprop` administrator commands).

Note: If you change the message selectors on a route, only incoming messages are evaluated against the new selectors. Messages pending in the server are re-evaluated only if the server is restarted.
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