Architecture Definition Document
A TOGAF deliverable that provides a comprehensive view of the architecture across all domains (business, data, application, technology), showing the baseline, target, and gap analysis for each domain.
Purpose
The Architecture Definition Document is the primary output of TOGAF Phase B-D, providing a complete and coherent architecture description that can be used to guide implementation. It brings together all architecture views into a single reference.
When to Use
Create during TOGAF Phases B, C, and D as each architecture domain is developed. It is the main deliverable of the architecture development cycle and feeds into implementation planning.
How to Build
Structure the document around the four TOGAF domains: Business Architecture, Data Architecture, Application Architecture, and Technology Architecture.
For each domain, document: the baseline (current state), the target (future state), and the gap analysis (what needs to change).
Use ArchiMate or UML diagrams to visualise each architecture domain. Show relationships between domains — how business processes map to applications, how applications use data, and how technology supports applications.
Include architecture decisions made during development, with rationale. Reference ADRs for detailed decision records.
Validate the architecture against the requirements specification to ensure all requirements are addressed.
Tips
- Use consistent notation across all domains for readability.
- Show cross-domain relationships — architecture domains are not independent.
- Include both diagrams and narrative — diagrams alone are insufficient.
- Validate against requirements to ensure completeness.
- Keep it maintainable — structure for easy updates as the architecture evolves.
Common Mistakes
- Treating domains in isolation without showing cross-domain relationships.
- Not including gap analysis, making it unclear what needs to change.
- Making it too detailed for its purpose — it should guide, not prescribe.
- Not validating against requirements, potentially missing gaps.
- Creating a document so large that nobody reads or maintains it.
Government Context
In UK government, the Architecture Definition Document supports spend control submissions and architecture governance. It should demonstrate alignment with cross-government reference architectures and the Technology Code of Practice. For major programmes, it provides the technical evidence for IPA gateway reviews.