Abstract
Aircraft maintenance manuals are written in a controlled language called ASD-STE100: about nine hundred approved words, fifty-three writing rules, one meaning per word. It exists because a misread instruction can bring an aircraft down. This article announces Mechanical: the Coherent Dictionary of Simple English rendered in that same discipline, plus the vocabulary extension that makes it possible. A moral constitution has the same requirement as a maintenance manual — it must not be misreadable — and a harder vocabulary problem, which turned out to be the interesting part.
What The Aerospace Dictionary Cannot Say
The approved word list of ASD-STE100 Issue 9 is a portrait of its world. It has words for valves, torque, corrosion, and inspection intervals. Rendering all 192 terms of the dictionary into it, and measuring the result, produced a finding we did not expect to be so clean: the standard has almost no words for time, speech, truth, life, or justice. Not because aerospace engineers do not value those things — because a wing does not need them.
A moral constitution needs exactly them. So Mechanical extends the base standard the way the standard itself says to: declared technical vocabulary, one meaning per word. 535 added words in ten groups — words of the moral doctrine, of mind, of speech and truth, of time, of life and death, of society, of the world, of action, of quality, and the small grammar words. Each one carries a one-line meaning in the aerospace style.
Seven Words, Two Worlds
Seven words are in the aerospace dictionary already, but Ultimate Law gives them a different single meaning. The contrast is the whole project in miniature:
- RIGHT — aerospace: “on the east side when you look north.” Ultimate Law: a named boundary that others must not cross without consent.
- AGENT — aerospace: one of a group of materials made to do a specified task. Ultimate Law: something that can form intentions, make decisions, and initiate actions.
- VALUE — aerospace: a quantity that is calculated or given. Ultimate Law: what an agent considers important — no one can measure it from outside.
- GOOD, FREE, PROPERTY, DAMAGE — the same pattern: a machine sense on one side, a moral sense on the other, and one meaning per word inside each world.
Same seven words. On one side of the table they describe an airframe; on the other, a moral universe. Controlled language is what keeps them from blurring.
Machine-Checkable Morality
The point of a controlled language is that conformance is checkable. Every sentence of Mechanical passes mechanical gates: 25 words or fewer, six sentences per paragraph, active voice, no semicolons, no contractions, and — the hard one — vocabulary closure: every single token is an approved word, a term of the dictionary, or a declared word of the extension. Zero residue. The whole language is 1,175 words, and you can read every one of them on one page.
The Law itself is the one exemption. It appears verbatim, by its own clause: “it cannot be changed, all the rest is commentary.” Everything else bends to the discipline; the anchor does not.
Where To Read It
- The dictionary in Mechanical — all 192 terms, in the orbit next to Esperanto, under the glyph ≡.
- All the words of Mechanical — the complete word index: terms, declared words with their meanings, the seven overridden words, and the base words.
- The dictionary as data — JSON and XML sit in the language orbit too. A controlled language for moral concepts should be readable by the minds most likely to need one.
The base standard is ASD-STE100 Issue 9, from the Aerospace, Security and Defence Industries Association of Europe. The specification is free from asd-ste100.org, and it is very good. Their word list is theirs and is not reproduced anywhere on this site; the extension declares only our own words.
If it matters, control the language.