Signal-Driven Development (SDD)

A solo-practitioner methodology for rigorous Domain-Driven Design with a measurable definition of done: zero unresolved gaps.

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Signal-Driven Development extends DDD with a structured convergence process, diagnostic feedback loops, and a definition of done that DDD has never had. SDD was developed through months of rigorous domain modeling across production systems -- complex domains with regulatory concerns, event-sourced architectures, and cross-context dependencies. The methodology emerged from practice, not theory.

Every domain goes through iterative passes. Each pass produces a domain specification, a gap report, and a gap resolution log. Gaps are signals, not verdicts. The architect reads, investigates, and resolves. The gap count must decrease across passes. The process terminates when no unresolved gaps remain.

The Convergence Trajectory

Across eight production domains, the typical trajectory:

Pass	Typical Gap Count	What Happens
1	15--35	Initial extraction. Structural errors, missing invariants, heuristic violations surface.
2	5--10	Focused resolution. Real architectural decisions get made and documented.
3	0--3	Final convergence. Residual tradeoffs resolved or consciously accepted.

Some domains require 4--5 passes. The invariant is convergence: each pass must reduce the gap count. If it doesn't, the specification is diverging -- and that non-convergence is the most important signal the process can produce.

Wiki Contents

Methodology

• Methodology Overview -- What SDD is, why it exists, and how it works
• Convergence Model -- The iterative three-pass convergence process
• Gap Categories -- The four diagnostic categories (SG, HG, LG, DG)
• Heuristic Thresholds -- Measurable thresholds sourced from DDD literature
• Severity Model -- ERROR vs WARNING classifications
• Glossary -- Key terms and definitions

Templates

• Templates Overview -- The four core SDD templates
• Template: Domain Specification -- Expressing the domain model in DDD building blocks
• Template: Gap Report -- Diagnostic evaluation against four gap categories
• Template: Gap Resolution Log -- Documenting resolution decisions with rationale
• Template: Architecture Palette -- Visual projection using Mermaid diagrams

Worked Examples

• Worked Example: Veterinary Clinic -- Complete three-pass convergence (18 → 5 → 0 gaps)

Getting Started

• Quick Start Guide -- Get started with SDD in five steps
• Scaffolding Script -- Automate domain analysis setup with init-domain.sh

Community

• Contributing -- How to contribute worked examples and improvements

• Changelog -- Methodology version history

• Lineage -- DDD community lineage and influences

• Blog Series -- Companion blog posts on Hashnode

• FAQ -- Frequently asked questions