aDNA vs. Johnny.Decimal
Two systems for organizing files — one uses a universal numbering scheme, the other uses a typed triad with agent governance.
Overview
aDNA
A knowledge architecture standard (§1) that sorts content into three directories (what/, how/, who/) using the question test. Within each leg, typed entity directories (concepts, missions, sessions, etc.) provide further structure. Navigation is governed by AGENTS.md files and typed frontmatter. Designed for AI-agent collaboration on projects.
Johnny.Decimal
A file organization system by Johnny Noble that assigns every file a unique number in a two-level hierarchy: 10 areas (10-19, 20-29, etc.) containing categories (11, 12, 13, etc.). Each item gets an ID like 23.04 (area 20-29, category 23, item 04). The numbering is the navigation — you find things by number, not by browsing directories. Designed for individuals and small teams managing digital files.
Comparison
| Dimension | aDNA | Johnny.Decimal |
|---|---|---|
| Organizing principle | 3 triad legs by question type | 10 numbered areas, unlimited categories |
| Navigation | Directory names + AGENTS.md routing | Numbers: find 23.04 by its ID |
| Agent support | Native: governance files, convergence model, typed entities | None: numbering aids humans, not agents |
| Flexibility | Fixed triad + extensible entity types | Flexible: you define your own areas and categories |
| Scale limit | Unlimited: federated across instances | 10 areas × 10 categories = 100 categories max |
| Semantic meaning | Directory names describe content (e.g., what/concepts/) | Numbers are opaque — you need the index to know what 23 means |
| Learning curve | Moderate: spec, frontmatter, governance | Low: learn the numbering convention, apply it |
| Multi-project | Each project is an aDNA instance | Each project gets its own number space |
Where aDNA Excels
- Semantic navigation: Directory names tell you what’s inside.
what/concepts/is self-describing.23.04requires an index lookup. - Agent routing: AGENTS.md at each directory tells agents whether to load or skip. Johnny.Decimal numbers mean nothing to an agent.
- Typed knowledge: aDNA entities have schemas, frontmatter, and typed I/O. Johnny.Decimal files are untyped.
- Federation: aDNA objects can be shared across projects with FAIR metadata and
lattice://URIs. Johnny.Decimal numbers are local. - No category ceiling: aDNA can add unlimited entity types via the base/extension pattern. Johnny.Decimal is capped at 100 categories.
Where Johnny.Decimal Excels
- Universal applicability: Works for any files — tax documents, project assets, recipes, music. aDNA is purpose-built for knowledge projects.
- Instant lookup: Know the ID, find the file.
32.07is unambiguous. aDNA requires navigating directory paths. - Dead-simple rules: “10 areas, 10 categories per area, sequential numbering.” The system fits on an index card.
- Tool-agnostic: Works in any filesystem, any OS, any app. No frontmatter, no governance files, no agent tooling required.
- No overhead: Create a folder, assign a number. No AGENTS.md, no templates, no session files.
- Physical+digital parity: Johnny.Decimal works for physical filing cabinets too. aDNA is digital-only.
When to Choose Which
| If you need… | Choose |
|---|---|
| A system for organizing diverse personal/business files | Johnny.Decimal |
| A knowledge architecture for AI-agent projects | aDNA |
| Instant lookup by ID across all your files | Johnny.Decimal |
| Typed, governed, machine-queryable knowledge | aDNA |
| Something you can explain in 2 minutes | Johnny.Decimal |
| Multi-agent collaboration with federation | aDNA |
| Physical + digital file organization | Johnny.Decimal |
| Operational infrastructure (sessions, missions, campaigns) | aDNA |
These serve genuinely different purposes. Johnny.Decimal organizes files; aDNA organizes knowledge for agent collaboration. A user might apply Johnny.Decimal to their personal filing while using aDNA for project knowledge.
Sources
- johnnydecimal.com — Johnny.Decimal system documentation
- Johnny Noble, “A system to organise your life” — method introduction
- aDNA Standard v2.1, §3 (Triad Architecture), §4.5 (AGENTS.md) — aDNA specification
Related
- The Triad — aDNA’s three-category principle (vs. Johnny.Decimal’s numbered areas)
- Question Test — how aDNA sorts content (vs. Johnny.Decimal’s numbering assignment)
- Ontology — the typed entity system that gives aDNA directories semantic meaning