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Johnny.Decimal: A Numbering System for Organising Everything

3 min read

Summary

Johnny.Decimal assigns a unique 2-decimal-place ID to every item (file, note, task, project) in your life using a three-level hierarchy: Areas (00–90), Categories (01–99 within each area), and IDs (item-level). The system imposes two hard constraints — max 10 areas, max 10 categories per area — which force deliberate information architecture and prevent accumulation of unmaintainable nested folders.

Johnny.Decimal 為生活中每個項目（文件、筆記、任務、專案）分配唯一的兩位小數 ID，使用三層層次結構：區域（00–90）、類別（各區域內 01–99）、ID（項目級別）。硬性限制：最多 10 個區域，每個區域最多 10 個類別——強制有意識的資訊架構。

Key Points

  • Structure: Area.Category.ID — e.g., 15.23 (Area 10–19, Category 15, ID 23). Always exactly 5 characters: two digits, decimal, two digits
  • Constraint = feature: limiting to 10 areas/10 categories forces you to decide what’s important rather than creating unlimited nesting. Unlimited nesting is the root cause of digital hoarding
  • Universal index: a central index.md or notebook links every ID to its location — the same ID appears in your filesystem, notes, email labels, and to-do manager. You search once, find everything
  • Cross-platform coherence: the same numbering works in Finder, Obsidian, Notion, Gmail labels, and physical filing. IDs become semantic anchors across tools
  • Works at home and work: same concepts apply whether you’re filing personal taxes or managing a software project

Insights

The core insight is that unlimited hierarchy is an anti-pattern: humans can only reliably navigate ~2 levels of nesting before they start “search as the only navigation.” Johnny.Decimal’s forced constraints make the system navigable by memory — you can learn that health-related documents live in 14.xx and never need to search. This is the same reason telephone numbers and postal codes work: the constraint creates memorability.

The practical weakness is maintenance discipline — the system works only if you consistently ID new items at capture time. It breaks down if you let items accumulate without IDs (similar to a GTD inbox that never gets processed).

Connections

Raw Excerpt

You assign a unique ID to everything in your life. These IDs help you stay organised. They impose constraints that make it harder to get lost.

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