Johnny Decimal and digital gardening, order and audience

Johnny Decimal is a system for organising files, created by John Noble. It borrows its logic from the Dewey Decimal Classification that libraries have used since the 1870s: instead of arranging things by name and hoping the arrangement survives, you give every thing a number, and the number becomes its address.

The scheme has exactly three levels, and the numbering makes them unambiguous.

• Areas are ranges of ten: 10-19, 20-29, and so on up to 90-99. An area is a broad division of your life or your work, at the level of Finance, or Clients, or Product.
• Categories are the individual numbers inside an area: 11, 12, 13. A category sits inside area 10-19 if and only if its number starts with a one. Many practitioners keep the round number (10, 20) for the area's own housekeeping and start real categories at 11.
• IDs are the items: 11.01, 11.02, up to ninety-nine of them in a category. An ID is one folder holding one thing, and it is the deepest the system goes.

A worked example is clearer than a description. This is one area of a small consultancy's drive.

Three properties follow from that and they are the whole payoff. The path is never more than two folders deep, so nothing can be buried. The number is stable even when the name is not, so renaming Northwind after an acquisition costs nothing and breaks no reference. And the address is short enough to say out loud, which is why teams that adopt the system end up writing it's in 22.01 in chat instead of pasting a link that will rot the next time somebody reorganises the drive.

The rule that makes people bounce off Johnny Decimal is also the rule that makes it work. You get at most ten areas, and at most ten categories inside each area. When the eleventh category presents itself, the system does not let you add it. You have to merge two existing ones, or promote something to its own area, or admit that the new thing is really a variation on something you already have.

Read as a storage limit that is absurd, since a hundred categories is not many. Read as a design constraint it is the entire method. An unbounded hierarchy has no cost to adding a folder, so folders get added at the moment of filing, which is exactly the moment you are least able to think about structure. The result is the drive everybody has seen: three plausible homes for the same document and no way to know which one it went into.

The system's own justification for ten is memory. A person can hold ten areas in their head and recognise them instantly. Nobody holds a hundred. The scheme is optimised for the moment you are looking for something, not the moment you are putting it away, and those two moments want opposite things: filing wants infinite precision, retrieval wants a small number of obvious choices.

One more piece is non-negotiable in practice. Johnny Decimal expects an index: a single document listing every number and what lives there. Without it the scheme is a private code, and the first colleague to encounter 22.01 has no way in. With it, the index becomes the map of the whole system, and it is usually the most-visited page in any team that runs one.

Johnny Decimal is excellent for anything with a filesystem underneath it and a filing problem on top of it. A personal drive, a shared team drive, a Confluence or SharePoint space, a set of physical archive boxes, a repository of contracts and invoices and policies. In all of those the unit is a document, each document has one natural home, and the pain is that nobody can find anything. That is precisely the pain a stable address removes.

It is a poor fit for a system whose unit is an idea. In a Zettelkasten or a set of evergreen notes, a note about the cost of context switching belongs equally to attention, to meetings, to management and to software estimation, and its value comes from being reachable from all four. A number forces you to pick one, and then the note is somewhere reasonable rather than everywhere it is useful. The linking approach solves that problem by not having the problem, which is the argument made in Zettelkasten and evergreen notes, and extended into navigable hubs in LYT and maps of content.

The second mismatch is churn. Johnny Decimal's stability is bought by not moving things, and a note system moves constantly: notes split, merge, get rewritten, change what they are about.

The combination most people land on is a division of labour rather than a winner.

• Johnny Decimal for the filesystem. Documents, exports, contracts, invoices, scans, project folders, anything you will look for by name in three years.
• PARA for the working layer. Actionability rather than address, so that what is live is visibly separate from what is reference. The method is in PARA and CODE, and PARA's own areas map onto Johnny Decimal's number ranges without much friction.
• Links and maps of content for the ideas. No numbers at all, in whichever tool you write in. Obsidian, Logseq and SiYuan all do this natively.

Numbering the note vault as well is a common beginner move and a common thing to abandon six months later. The usual compromise is to number only the parts that behave like an archive and leave the thinking unnumbered.

The framing most people are reaching for when they say digital garden comes from Mike Caulfield's 2015 talk The Garden and the Stream: A Technopastoral. Caulfield's contrast was between two ways of publishing on the web. The stream is the feed: posts in reverse-chronological order, each a finished statement, each obsolete within days, organised by when rather than by what. The garden is the wiki: pages revisited and revised, connected by meaning, with no front page announcing what is newest because newest is not the point.

Maggie Appleton's writing on digital gardens gave the idea its current shape and most of its vocabulary. The characteristic properties are consistent across gardens that work:

• Topological, not chronological. There is no timeline. Pages are reached through links and through index pages, and a page written two years ago is not thereby less current.
• Continuously revised. A page is edited in place rather than superseded by a follow-up post. The version you read is the current thinking, not a dated snapshot of it.
• Openly unfinished. Half-formed pages are published as half-formed. The garden shows work in progress rather than only the harvest.
• Densely linked. The value is in the connections, which is why gardens usually surface backlinks: what else in here points at this page.

Because unfinished pages are published, gardens need a way of telling the reader how much to trust any given one. The convention that spread widest is a three-stage maturity label, usually rendered as an emoji or a tag at the top of the page:

• Seedling. A rough capture. A few sentences, a quotation, a link, an idea recorded before it is understood. Read it as a note to self that happens to be visible.
• Budding. Worked on more than once. It has a shape and an argument, but claims may be unsupported and the writing is not addressed to you yet.
• Evergreen. Stable and maintained. Andy Matuschak's use of the term is the strict one: atomic, concept-oriented, densely linked, and written to be built on rather than finished. Evergreen does not mean done, it means reliable enough to depend on.

The labels are not decoration. They are what makes publishing unfinished work honest rather than careless, because they set the reader's expectation before the reader forms a judgement.

If your notes are already Markdown files, publishing them is a solved problem with three or four reasonable answers, differing mainly in how much of the work you want to own.

Two practical notes that apply whichever you pick. First, publish a subset, never the vault. Every one of these tools supports selecting what goes out, usually with a property in the note's front matter, and the default should be private with publishing as the explicit act. A vault contains client names, salary numbers, half-formed opinions about colleagues and the contents of your inbox, and a one-command deploy makes an accident cheap.

Second, expect broken links. The moment some notes are held back, the published ones link into nothing. Quartz and Flowershow both decline to render links to absent pages, but the underlying issue is editorial: a note written for yourself frequently depends on three notes you would never publish.