In short, the idea of Big "A" Systems Architecting in DoD suggests that the decisions on how to partition a system, connect those parts, and define the processes and rules that govern its evolution are the results of a highly concurrent process that includes the range of activities from modeling and documenting department-level strategic goals to the development of models that describe system solutions from an operational, functional, physical, and technical perspective.
The significance of the Big "A" systems architecting perspective is that it reveals opportunities to improve the overall acquisition process.
Systems architecting is part of the systems engineering design process that results in the partitioning of a system into components, the defining of interfaces among those components, and the processes that govern their change over time.
Emerging modeling methodologies present an opportunity for DoD to improve collaboration and productivity during the concurrent evolving stages of the Big "A" systems architecting process, and this can contribute to better acquisition decisions with concomitant improvement in acquisition outcomes.
My observation is that systems architecting in DoD is best understood from the perspective of the broader Big "A" acquisition enterprise that includes not only system developers, but strategy and policy makers, resource sponsors, and combat developers.
Systems architecting develops a deep understanding of the required system behavior that is traceable to an overall goal and achievable within established constraints.
The architecting process makes extensive use of heuristics ("rules of thumb" based on lessons learned from experimentation and experience) and judgment in order to deal with complexity, and places less emphasis on engineering analysis to decide on the best approach (see The Art of Systems Architecting by Mark W.
Models serve as the canvas on which the systems architecting process is realized.
Instead, program offices and the broader acquisition community must look at architecture (or systems architecting) as a proactive endeavor.
Accordingly, it might make sense that the DAS (or acquisition program manager) also controls the systems architecting process, and that this process proceeds in a linear fashion, starting with a set of stakeholder requirements and ending with an architectural description of a solution that provides the basis for the detailed design work to follow.
Certainly, the DAS plays a leading role in the architecting of defense systems, but I believe a broader perspective is needed, My observation is that the systems architecting process in DoD transcends the DAS and involves the other major DoD decision supports systems--the Joint Capabilities Integration Development System (JCIDS); the Planning, Programming, Budgeting, and Execution System (PPBES); as well other strategic operational-level planning and decision activities.