TOGAF approaches enterprise architecture as a way of improving business capability – which is why the first architecture development phase deals with the Business Architecture.
The ADM starts from a business perspective – with a strong business need identified in the Request for Architecture Work in the Preliminary Phase, and further refined into a Statement of Architecture Work and Architecture Vision in Phase A.
A key objective in the Business Architecture phase is to develop a Target Business Architecture that shows how the enterprise can achieve the Architecture Vision and address the Request for Architecture Work. Its second objective is to make a first-cut at identifying candidate Architecture Roadmap components to bridge the gap between the Baseline and Target Business Architectures.
TOGAF regards knowledge of the Business Architecture as a prerequisite for architecture work in other domains, such as Data, Application, and Technology.
It is Business Architecture that also demonstrates the business value and return on investment of architecture work to key stakeholders.
Business models, such as activity or process models, use case and class models, or node connectivity diagrams, extend business scenarios to map architecture from high-level to more detailed business requirements.
All three architecture development phases (B, C & D) follow similar steps.
It is important to reuse any available reference models, and tailor all outputs to address stakeholder viewpoints. Architects then develop a baseline and target description of the Business Architecture, and perform gap analysis to figure out how to make the transition from one to the other.
Enterprise Architecture TOGAF Video