Template: Architecture Palette

File: templates/architecture-palette.md

The architecture palette is a visual projection of the domain specification. It transforms the textual model into a diagram that reveals patterns invisible in prose -- an aggregate connected to everything, a context with no outbound events, a saga that spans contexts unnecessarily.

Purpose

The palette is both a communication artifact and a verification surface:

• Communication: Stakeholders can see the domain model at a glance without reading the full specification
• Verification: Visual patterns surface gaps that text cannot -- imbalanced contexts, isolated aggregates, missing reactive chains

Structure

Layout

Horizontal swimlane per bounded context. Inside each swimlane, building blocks are arranged to show the reactive chain:

Command → Aggregate → Domain Event → Policy/Saga → Command

Visual Conventions

Element	Shape	Notes
Aggregates	Rectangles	Name + invariant count
Commands	Arrows into aggregates
Domain Events	Arrows out of aggregates
Policies	Diamonds	Single event in, single command out
Sagas	Rounded rectangles	Multiple steps shown
Projections	Parallelograms	Events in, queries out
Cross-context flows	Dashed lines	Labeled with relationship type

Example Layout

[Context A]
  Command → Aggregate → Event
                          ↓
[Context B]        Policy → Command → Aggregate → Event
                                                    ↓
[Context C]                                  Saga → Command (step 1)
                                                  → Command (step 2)
                                                  → Completion Event

Building Block Summary

Context	Aggregates	Commands	Events	Policies	Sagas	Projections	Invariants
Total

Observations

Note any visual patterns the palette reveals:

• Imbalanced contexts (one context with 80% of the building blocks)
• Isolated aggregates (no inbound commands or outbound events)
• Missing reactive chains (events with no consumers)
• Cross-context coupling patterns

Implementation

Use any diagramming tool:

• Mermaid (recommended -- renders in GitHub, can be embedded in markdown)
• Whiteboard or physical drawing
• Excalidraw, draw.io, or other diagramming software

The worked example uses Mermaid. See Worked Example: Veterinary Clinic for a complete architecture palette.

When to Create

The architecture palette is optional but valuable:

• Simple domains (1--2 contexts): May not need a visual projection
• Complex domains (3+ contexts): Strongly recommended
• Final convergence pass: Best created at Pass 3 when the model is stable

Creating the palette too early (Pass 1) may waste effort since the model will change significantly. Creating it at convergence provides a stable verification surface.