What is a software architecture document?
A system analysis, design and architecture document describes a system at a high level: its context and logical architecture as diagrams, its components, integrations, data, security, deployment and the key decisions. For software, digital and integration concepts.
Also called: System analysis, design and architecture, System design document, SAD.
Why it matters
Architecture is decided early, whether anyone writes it down or not. Written down, each choice shows its alternatives, and the quality targets the system must meet are set before they are costly to change.
From context to decisions
The document is drawn from the PRD and from the same system model as the FRS.
- Context. The system as one box: who uses it and what it exchanges data with, as a diagram. In Ainna's document: the system in context.
- Structure. The logical architecture: its layers and components, and each component's responsibilities. In Ainna's document: the logical architecture; components and their responsibilities.
- Qualities. Quality attributes with targets, security, and the deployment and recovery objectives. In Ainna's document: quality attributes, security, deployment.
- Decisions. Each significant choice, with the alternatives considered and why this one won. In Ainna's document: architecture decisions.
What's inside
- The architecture in brief
- What drives it
- The system in context, as a diagram
- The logical architecture, as a diagram
- Components and their responsibilities
- Integration patterns
- Data and its stores
- Quality attributes, with targets
- Security
- Deployment and recovery objectives
- Architecture decisions
- Risks and transition
Where it fits
It is distilled from the PRD, and the same system model as the FRS.
It comes after Product Requirements Document (PRD) and Functional Requirements Specification (FRS).
Questions
What goes into a software architecture document?
Ainna's covers the system in context and its logical architecture, both as diagrams; the components and their responsibilities; how it integrates with other systems; its data and where it is stored; quality attributes with targets; security; deployment and recovery objectives; and the key architecture decisions with their alternatives.
What is a system context diagram?
One picture of the system as a single box, the people who use it and the systems it exchanges data with. It is the first diagram an architecture document needs.
What is an architecture decision record?
A short note for each significant choice: the decision, the alternatives considered, and why this one won.
Architecture document or FRS?
The FRS says what the system must do. The architecture document says how it is structured to do it, and how well it must perform.
Do the work in Ainna.
Ainna is where you frame a problem, explore ideas and test them against the evidence. When the work is done, this is how it is packaged: a software architecture document, written from your own analysis, about your own idea.
Which documents you can create depends on your plan.
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