In which part of the ADM cycle do the earliest building block definitions start as abstract entities?

Phase A, the Architecture Vision phase, is where the initial high-level architectural description and an abstract architecture vision are created. At this stage, building blocks are identified in an abstract, conceptual manner to define the scope and vision without detailing their implementation.

The Preliminary Phase focuses on preparing the organization for architecture work and establishing the ADM, not defining abstract building blocks.

Phases B, C, and D (Business, Information Systems, and Technology Architectures) are where building blocks are further developed and refined into more concrete, detailed components, not where they first appear as abstract entities.

Phases G and H (Implementation Governance and Architecture Change Management) deal with implementation oversight and managing change, long after initial abstract building block definitions.

Phases E and F (Opportunities and Solutions and Migration Planning) focus on identifying delivery vehicles and creating migration plans, not the initial abstract definition of building blocks.