examples/spatial-arm.umsg
%unimsg 0 spatial/arm/v0 · 292 lines · 10070 bytes of text · 4910 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 spatial/arm/v0
-- A six-axis robot arm, hand-authored in @vocab/spatial/v0.
--
-- The vocabulary was read off sixteen formats and no file, and docs/42 tested
-- it by transcribing five specifications rather than converting five files.
-- This is the other test, and the one @vocab/vocabulary/v0's landing checklist
-- asks for: small, written by hand, and exercising the thing the whole design
-- rests on — a frame graph acting as a kinematic chain.
--
-- WHAT IT DELIBERATELY STRAINS. A joint per frame, with limits in a unit that
-- is not the frame's. A measured frame beside authored ones, so :tolerance and
-- :measurement are both used rather than described. A collision instance
-- alongside the visual ones, which is the URDF construct docs/42 found had
-- nowhere to go. A morph target driven by a declared parameter, which is the
-- glTF construct that broke the motion sketch. And a body carrying mass and an
-- inertia tensor, which is a fact and not a simulation.
--
-- Every pose here is a translation and an identity rotation, and that is not
-- laziness: a rest pose is where the mechanism sits with every joint at zero,
-- and the interesting rotations belong in a take — which is the SECOND BLOCK of
-- this same document, not a second file.
spatial @spatial/arm/v0 {
title "Six-axis arm at rest"
status :draft
at 2026-08-30
description "A six-axis industrial arm in its zero configuration: a base
column, two link shells, a wrist ball and a gripper blade, with
a coarse collision hull over the upper arm and a camera mounted
on the base."
-- A micrometre, on a machine tool. The number is a fact about how finely
-- this document records and the transcript is rounded onto it.
precision {
length mm 0.001
unitless 0.000001
rounding :half-even
}
canonical-frame -> @frames.base
measurement {
instrument "Faro Vantage tracker"
at 2026-08-30
method "the camera mount surveyed against the base flange; every other
frame is authored from the drawing"
}
frames {
base {
unit :m
handedness :right
up :z
}
shoulder {
parent -> @frames.base
pose { translate [ 0, 0, 0.1625 ] }
joint {
kind :revolute
axis [ 0, 0, 1 ]
limit { lower deg -180, upper deg 180 }
effort nm 150
velocity 3.15
}
}
upper-arm {
parent -> @frames.shoulder
pose { translate [ 0, 0.138, 0 ] }
joint {
kind :revolute
axis [ 0, 1, 0 ]
limit { lower deg -150, upper deg 150 }
}
}
forearm {
parent -> @frames.upper-arm
pose { translate [ 0, -0.131, 0.425 ] }
joint {
kind :revolute
axis [ 0, 1, 0 ]
limit { lower deg -150, upper deg 150 }
}
}
wrist {
parent -> @frames.forearm
pose { translate [ 0, 0, 0.392 ] }
joint {
kind :revolute
axis [ 0, 1, 0 ]
limit { lower deg -180, upper deg 180 }
}
}
tool-flange {
parent -> @frames.wrist
pose { translate [ 0, 0.127, 0 ] }
joint { kind :fixed }
}
-- The one frame in this document that was measured rather than drawn, and
-- the reason :measurement is present at all.
camera-mount {
parent -> @frames.base
pose { translate [ 0.3, -0.25, 0.9 ] }
tolerance { position mm 2 }
}
}
parameters {
gripper-open {
doc "how far the blade is spread, from closed to fully open"
default 0
lower 0
upper 1
}
}
materials {
steel { base-colour "#8a8f98", metallic 1, roughness 0.4 }
warning { base-colour "#d9a441", metallic 0, roughness 0.6 }
}
geometry {
base-column { cylinder { radius 0.075, length 0.1625 } }
upper-arm-shell { box { extent [ 0.09, 0.09, 0.425 ] } }
forearm-shell { box { extent [ 0.08, 0.08, 0.392 ] } }
wrist-ball { sphere { radius 0.045 } }
collision-hull { box { extent [ 0.1, 0.1, 0.45 ] } }
-- A five-vertex blade, and the only mesh here. Its :targets entry is what
-- a declared parameter is for: the tips spread and nothing else moves.
gripper-blade {
mesh {
positions [ -0.02, -0.02, 0,
0.02, -0.02, 0,
0.02, 0.02, 0,
-0.02, 0.02, 0,
0, 0, 0.06 ]
indices [ 0, 1, 2,
0, 2, 3,
0, 1, 4,
1, 2, 4,
2, 3, 4,
3, 0, 4 ]
attributes {
face { kind :uv, values [ 0, 0, 1, 0, 1, 1, 0, 1, 0.5, 0.5 ] }
}
targets {
open {
deltas [ -0.01, -0.01, 0,
0.01, -0.01, 0,
0.01, 0.01, 0,
-0.01, 0.01, 0,
0, 0, 0 ]
parameter -> @parameters.gripper-open
}
}
}
}
}
bodies {
forearm-body {
doc "the forearm casting, weighed rather than modelled"
frame -> @frames.forearm
mass kg 3.7
centre-of-mass [ 0, 0, 0.196 ]
inertia [ 0.0666, 0.0666, 0.0047, 0, 0, 0 ]
}
}
scene [
{ geometry -> @geometry.base-column, frame -> @frames.base, purpose :visual, material -> @materials.steel }
{ geometry -> @geometry.upper-arm-shell, frame -> @frames.upper-arm, purpose :visual, material -> @materials.steel }
{ geometry -> @geometry.forearm-shell, frame -> @frames.forearm, purpose :visual, material -> @materials.steel, body -> @bodies.forearm-body }
{ geometry -> @geometry.wrist-ball, frame -> @frames.wrist, purpose :visual, material -> @materials.steel }
{ geometry -> @geometry.gripper-blade, frame -> @frames.tool-flange, purpose :visual, material -> @materials.warning }
{ geometry -> @geometry.collision-hull, frame -> @frames.upper-arm, purpose :collision }
]
-- The arm at rest, asserted rather than described. The flange sits at
-- y = 0.138 - 0.131 + 0.127 and z = 0.1625 + 0.425 + 0.392, which is the
-- kind of sum a reader should not have to do and a checker should.
checks [
{
doc "the tool flange sits where the drawing says, with every joint at zero"
assert :position-of
of -> @frames.tool-flange
in -> @frames.base
expect [ 0, 0.134, 0.9795 ]
}
{
doc "the camera sees the base from where it was surveyed"
assert :position-of
of -> @frames.camera-mount
in -> @frames.base
expect [ 0.3, -0.25, 0.9 ]
}
{
doc "nothing was silently dropped: five visual instances and one collision hull"
assert :entry-count
of -> @spatial/arm/v0
expect 6
}
]
}
-- The take that drives it, BESIDE it rather than in a second file. It carries
-- no :binds and no digest: two blocks in the same bytes cannot drift apart, so
-- there is nothing for a pin to defend against. See
-- a-take-belongs-beside-its-scene in @vocab/motion/v0.
motion @motion/arm-sweep/v0 {
title "Arm sweep, one second"
status :draft
at 2026-08-30
doc "the shoulder sweeps 45 degrees while the forearm drops 30 and the
blade opens, in one second at ten hertz"
interval [ 0, 1 ]
rate Hz 10
channels [
-- the shoulder sweeps 45 degrees about its own axis
{
drives -> @frames.shoulder
interpolation :linear
rotate [
0.00000000, 0.00000000, 0.00000000, 1.00000000,
0.00000000, 0.00000000, 0.03925982, 0.99922904,
0.00000000, 0.00000000, 0.07845910, 0.99691733,
0.00000000, 0.00000000, 0.11753740, 0.99306846,
0.00000000, 0.00000000, 0.15643447, 0.98768834,
0.00000000, 0.00000000, 0.19509032, 0.98078528,
0.00000000, 0.00000000, 0.23344536, 0.97236992,
0.00000000, 0.00000000, 0.27144045, 0.96245524,
0.00000000, 0.00000000, 0.30901699, 0.95105652,
0.00000000, 0.00000000, 0.34611706, 0.93819134,
0.00000000, 0.00000000, 0.38268343, 0.92387953,
]
}
-- and the forearm drops 30 degrees while it does
{
drives -> @frames.forearm
interpolation :linear
rotate [
0.00000000, -0.00000000, 0.00000000, 1.00000000,
0.00000000, -0.02617695, 0.00000000, 0.99965732,
0.00000000, -0.05233596, 0.00000000, 0.99862953,
0.00000000, -0.07845910, 0.00000000, 0.99691733,
0.00000000, -0.10452846, 0.00000000, 0.99452190,
0.00000000, -0.13052619, 0.00000000, 0.99144486,
0.00000000, -0.15643447, 0.00000000, 0.98768834,
0.00000000, -0.18223553, 0.00000000, 0.98325491,
0.00000000, -0.20791169, 0.00000000, 0.97814760,
0.00000000, -0.23344536, 0.00000000, 0.97236992,
0.00000000, -0.25881905, 0.00000000, 0.96592583,
]
}
-- the blade opens across the whole sweep. A parameter, not a frame
{
drives -> @parameters.gripper-open
interpolation :linear
values [ 0.00000000, 0.10000000, 0.20000000, 0.30000000, 0.40000000, 0.50000000, 0.60000000, 0.70000000, 0.80000000, 0.90000000, 1.00000000 ]
}
]
checks [
{
doc "the blade is fully open at the end"
assert :value-at
of -> @parameters.gripper-open
at 1
expect 1
}
{
doc "every sample of the shoulder is inside the limit the scene declares"
assert :limit-holds
of -> @frames.shoulder
at 0
expect true
}
]
}
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11 d7 6b 66 72 61 6d 65 73 2e 62 61 73 65examples/spatial-arm.umsg 4910 bytesEvery 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. |
| — | — | — | 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. |