The next step in the planning process is project plan development for all of the lowest-level projects in the program hierarchy. With awareness of the program objectives and constraints, each project team builds a thorough bottom-up project plan.
Because the projects are all interrelated, many of the dependencies for activity sequencing will link to other projects. For each project, identify all required inputs coming from outside the project that could slow down or stop it.
Document all your external input dependencies as program interfaces. You are the consumer who needs the input, so begin a dialog with the leader of the project that you expect will produce it.
Work to resolve the interface by requesting commitment ...