Projects are guided while working within architecture by the Project Start Architecture (PSA).
The PSA is a translation of the general architecture principles and models to project specific directives. The general architecture is tailored to the specific challenges of the project. This provides a concrete framework within which the project is to be executed.
The objective of the PSA is to deliver a practical; relevant and well defined scope for the project so that the project deliverables fit into the overall structure within the organization.
The PSA is defined at the start of a project. It is a collaboration between the architects and the project team.
The PSA together with the Execution Plan form the project start-up documentation.

The Project Start Architecture (PSA) template is available here