Closed layers

[seddonym]

"A closed layered architecture means that any given layer (or tier) can only use the services of the next immediate layer, whereas in an open layer architecture a given layer can make use of any of the layers (or tiers) below it. Closed layer architecture promotes independence between layers by reducing dependencies."
https://stackoverflow.com/a/904280/1005499

The contract might look something like this:

My contract:
    containers:
        - mypackage.apps.foo
        - mypackage.apps.bar
    layers:
        - api
        - [closed] views
        - [closed] forms
        - models

This would prevent anything from anywhere else in the codebase from reaching down below the closed layers to layers underneath. This would effectively make api and views in each app a public interface, while forms and modules are private to the app.