Environments fulfil several roles. They are containers for the Packages that are Persistate applications. An Environment has two collections of Packages. The ProductPackages collection contains the packages which have been created in this environment. An Environment is the development environment for the packages in this collection. AvailablePackages is an associated collection containing all the packages in the ProductPackages collection, plus any number of other packages which have been imported into the environment. These others will be in the ProductPackages collection of another environment, in the same or another domain.

Environments are also the root objects for all the persistent sub-trees used by its packages. When you develop or import a package in an environment, the package's defined persistent tree is instantiated within the environment. When you run the package, your application sees just this persistent tree with the defined singletons at the top, accessible through the generated "The" class.

This last facility of course begs the question of security - although it is possible, we don't want to allow any application to freely access any other's persistent data. Environments also deal with this issue, by allowing the definition of Permits. Permits allow precise access to the data within specific portions of the persistent tree, and the Operations which act on the objects within it. These permits can be granted to the Principals which represent the agents (e.g. users) which perform operations on persistent data.

Environments are also used as the unit of service for Persistate servers. This means that, at least, a particular Persistate server provides service for all the available packages in a single environment, though it may service more than one environment. Each environment has its own AccessUri used to access this service.