You can't run the ADM until the organisation is ready to run it. The Preliminary Phase is the 'set-up' that happens once (and is revisited periodically) — before any specific architecture project. Skip it and later phases have no principles, no governance, no agreed method, and no team.

Think of it as installing the architecture capability, versus Phase A which starts a specific architecture project.

The Preliminary Phase determines where, what, why, who, and how architecture is done in the enterprise. Its objectives: define the enterprise scope, identify key drivers, define the architecture principles, establish the Organizational Model for Enterprise Architecture, define the Architecture Framework (tailor the TOGAF Standard and any other frameworks), and set up the initial governance and tools.

The main outputs are: the Organizational Model for Enterprise Architecture, a tailored Architecture Framework (including principles), an initial Architecture Repository, restatement of business principles/goals/drivers, and a Request for Architecture Work may be received here to trigger Phase A.

Architecture principles — governed statements of belief (name, statement, rationale, implications) — are a defining Preliminary output; they steer every later decision.

Preliminary establishes the capability that Phase A then uses to start a project. The governance framework set up here is exercised throughout the ADM (sharply in Phase G). Tailoring here decides which Series Guides and techniques you'll apply.