Location
Entities can be provisioned/started in the location of your choice. Brooklyn transparently uses jclouds to support different cloud providers and to support BYON (Bring Your Own Nodes).
The implementation of an entity (e.g. Tomcat) is agnostic about where it will be installed/started. When writing the application definition specify the location or list of possible locations (Location instances) for hosting the entity.
Location instances represent where they run and indicate how that location (resource or service) can be accessed.
For example, a JBoss7Server will usually be running in an SshMachineLocation, which contains the credentials and address for sshing to the machine. A cluster of such servers may be running in a MachineProvisioningLocation, capable of creating new SshMachineLocation instances as required.