`profiles/v0.umsg`

%unimsg 0 profile/v0 · 50 lines · 2248 bytes of text · 1071 bytes canonical · the raw file

Point at anything below — a sigil, a literal, a brace — and the card says what it is. Keyboard: tab through the document. Every explanation is also printed in full beneath the source.

%unimsg 0 profile/v0

-- The v0 conformance profile, expressed in unimsg rather than in prose.
--
-- Restrictions used to live as English in docs/12, which meant the only way
-- to enforce one was to hardcode a check. As a document a profile is
-- content-addressed, versionable, composable, and checkable by generic code.

profile @unimsg/v0 {
  doc "Conformance profile for unimsg v0."

  -- D10/F6: native float equality diverges from byte equality. -0.0 and 0.0
  -- are byte-distinct but compare equal; NaN and NaN are byte-identical but
  -- compare unequal. Banning float keys removes the divergence class rather
  -- than asking every implementer to handle it.
  --
  -- Bytes joined float on the same argument, having been allowed here for
  -- longer than anything implemented it. A byte-string key is unhashable in
  -- some hosts and indistinguishable from a text key in others, which is the
  -- same divergence wearing different clothes. Nothing in the repository ever
  -- wrote one; six implementations refused them in six different ways, and
  -- the profile said they were fine.
  keys {
    allow  [ :text, :int ]
    reject [ :float, :bytes ]
    reason "F6 — native float equality diverges from byte equality, and a bytes key diverges from a text key the same way"
  }

  -- Encoding-level rules. These cannot be checked from a decoded value; the
  -- validator needs the bytes.
  encoding {
    determinism    :required
    duplicate-keys :reject
  }

  limits {
    doc "WHAT max-depth COUNTS, settled 2026-09-02: containers of the value
         model. The document body is depth 0 and each map or sequence entered
         adds one, so a table row's cells are two below the table's parent —
         the sequence, then the row's map. Tags, annotations, qualifiers,
         decimals, references and extensions add nothing, because they are how
         a scalar is written and not what an author nests. This is the count
         `umsg profile` applies. A decoder's stack-safety cap is a different
         number, measured on the encoding, where a decimal is a tag around a
         two-element array; it must sit comfortably above this one, and the
         implementer's guide says how far."
    max-depth 500
  }
}

The canonical encoding

Produced by the reference encoder when this page was built. Decoding these bytes and printing them in the text form returns the document above, byte for byte — that round trip is the claim the whole format rests on.

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69 6d 73 67 2f 76 30 a4 63 64 6f 63 78 22 43 6f 6e 66 6f 72 6d 61 6e 63
65 20 70 72 6f 66 69 6c 65 20 66 6f 72 20 75 6e 69 6d 73 67 20 76 30 2e
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68 65 6e 63 6f 64 69 6e 67 a2 6b 64 65 74 65 72 6d 69 6e 69 73 6d da 00
01 11 d4 68 72 65 71 75 69 72 65 64 6e 64 75 70 6c 69 63 61 74 65 2d 6b
65 79 73 da 00 01 11 d4 66 72 65 6a 65 63 74

canonical CBOR for profiles/v0.umsg 1071 bytes

Every construct on this page

The formal columns are read from the specification when this page is generated. The last column is this site's plain-language gloss and is not normative — where they differ, the specification is right.

construct	glyph	carries	example	gloss
:annotation	—	—	—	A bare name qualifying the value after it—for example a language tag or a unit such as `kg`. It is not a value itself; a bare name with nothing after it is an error, not a guess.
:array	`^`	type, or type:shape; then [ elements ]	`^f64 [ 1.5, 2.5 ] or ^i16:2x3 [ … ]`	A packed, homogeneous numeric array. The `^` marker gives every element its type and may also give the row-major shape: `^f64:2x3 [ … ]`.
:array-element	—	—	—	One element of a typed array. Its type comes from the `^` marker, so `1.5` inside `^f64` is binary64 rather than an exact decimal.
:array-missing	—	—	—	A missing position in a typed array. `null` here is not an element value: it adds a validity mask while preserving the array's shape.
:block	—	—	—	A block: named pairs, in braces. Its keys are sorted in the encoding and shown here as written.
:bytes	`~`	encoding:data	`~hex:ff00 or ~b64:iVBORw0KGgo=`	Raw octets, carried as octets. No base64 tax, no pretending they are text.
:comment	`--`	to end of line	`-- a note`	A note for people. It travels with the pair it precedes and never reaches the bytes.
:decimal	—	—	—	An exact decimal. 19.99 is nineteen and ninety-nine hundredths, not the nearest double to it.
:extension	`!`	name, then value	`!acme/hint { zone 4 }`	A qualifier this reader may not know. It survives the round trip intact, and stays legible on the way past — the rule that separates an extension from a private convention.
:float	—	—	—	A binary float, marked so it can never be mistaken for the exact decimal beside it.
:hash	`#`	algorithm:hex	`#sha256:deadbeef`	The digest of some content, with the algorithm said out loud so it is still meaningful in ten years.
:header	`%`	unimsg only	`%unimsg 0 label`	Declares the format version and what this document is. Optional, and useful exactly when a file arrives without context.
:identifier	`@`	word	`@ord-88213`	Gives this value a name, so another document can point at it without copying it.
:integer	—	—	—	A whole number of any size. Past 2^53 it is still exact, which is the whole reason this is not JSON.
:key	—	—	—	A field name: the first thing in a pair. It is bare when possible and quoted when needed, and names the content without becoming part of the value.
:reference	`->`	an identifier or a path	`-> @cust-4471, -> @lexicon.entries.kitāb`	Points at a name. Nothing follows it while reading — resolution is somebody else's job, deliberately.
:reserved-literal	—	—	—	One of six bare words that are values rather than names. The list is fixed, so no value is coerced by what it looks like.
:sequence	—	—	—	An ordered list. Order is preserved and is meaning.
:string	—	—	—	Text. May span lines, so prose does not have to be escaped into one.
:symbol	`:`	word	`:dispatched`	A name from a fixed vocabulary, not free text. `:high` is a value someone chose; "high" is a phrase someone typed.
:table-row	`\|`	cells	`\| sku qty`	One record of a table. A table is sugar for a sequence of blocks with the same keys, and encodes identically to the longhand.
:timestamp	—	—	—	A temporal value at the precision written. `2026-08` stays a month, and `03:52` stays a wall-clock time; neither is widened into an invented instant.