The Space Repository is a centralized database
containing information about all active devices and services in an Active
Space. It keeps this information up-to-date by listening on the Presence
Channels, where events about new entities, as well as entities that are no
longer active, are sent. All entities in the system have an XML
description, which includes properties such as entity type, name, location, etc.
The Space Repository can be queried for entities based on these
properties. For example, an application may
require two large displays. These components can be found by querying the
Space Repository for two display that satisfy a particular dimension
constraint. Note that in different spaces, different displays may result
from such a query, depending on what resources are available.