AI Assistant ASD-STE100 Writing Rule

This document states the writing rule for an AI assistant. The rule applies to Claude, GitHub Copilot, and a similar tool. The rule is ASD-STE100, Simplified Technical English (STE).

Table of Contents

• Table of Contents
• What ASD-STE100 Is
• The Rule
• Core Writing Rules for the Assistant
  • Sentence Length
  • Verb Forms
  • Voice
  • Structure
  • Words
  • Contractions
• How the Rule Applies to Each Output Type
• How the Assistant Performs This Work
• Limits of This Rule

What ASD-STE100 Is

ASD-STE100 is an international standard for technical writing. The Aerospace, Security and Defence Industries Association of Europe (ASD) owns the standard. STE has two parts:

• Part 1: 53 writing rules, in 9 sections.
• Part 2: a controlled dictionary of about 900 approved words.

STE removes ambiguity from technical text. STE also makes technical text easier to translate. STE is not a simple style choice. STE needs strong English skill to apply correctly.

The Rule

Apply full, strict STE to every written deliverable. A written deliverable is a document, a pull request or merge request body, SOX evidence, a commit message, or an error message.

In casual chat, keep the short-sentence, plain-word discipline. In casual chat, a contraction is permitted, and the tone can stay informal and friendly.

This split has one purpose. A permanent artifact must meet the full standard. A live conversation can stay natural, and can still stay clear.

Core Writing Rules for the Assistant

Sentence Length

• A procedure has a limit of 20 words per sentence. A procedure gives an instruction, a numbered step, or a command.
• A description has a limit of 25 words per sentence. A description explains a fact, a cause, or a background detail.
• Never mix a procedure and a description in the same passage.

Verb Forms

Use only these verb forms:

Form	Example
Infinitive	to install
Imperative	Install...
Simple present	installs
Simple past	installed
Simple future	will install
Past participle, as an adjective only	the installed component

Three modal verbs are approved: CAN, WILL, and MUST. Five modal verbs are not approved: could, may, might, should, and would. Replace a not-approved modal with an approved form. For example, replace "should" with "must", except inside a document that uses RFC 2119 keywords on purpose.

Voice

Use the active voice. A description can use the passive voice, only when the actor is not known.

Structure

• Keep every subject, every verb, and every article in a sentence. Do not omit a sentence part for brevity.
• State a condition before a command: "If the build fails, revert the commit." Do not state the command first.
• Use a vertical list for a complex sequence.
• Give each paragraph one topic, with the topic sentence at the start. Keep a paragraph to 6 sentences or fewer.
• Limit a multi-word noun to 3 words. For a longer technical term, write it in full once, then use a shorter form or a hyphen.

Words

• Use plain, common words. Prefer a short word over a long word.
• Do not use jargon, slang, or a regional term.
• Use one word for one meaning. Do not use two different words for the same item.
• Use American English spelling in prose. Keep an identifier, a field name, or an API name in its original spelling.
• Do not use a Latin abbreviation. Write "for example" instead of "e.g.", and "that is" instead of "i.e.".
• Do not use "he" or "she" as a generic pronoun. Use gender-neutral language at all times.

Contractions

Do not use a contraction in a written deliverable. Write "do not", not "don't". Write "cannot", not "can't".

How the Rule Applies to Each Output Type

Output type	Rule that applies
Documentation	Full descriptive rules. A 25-word sentence limit. One topic per paragraph.
Pull request or merge request body	Descriptive rules for the reasoning. Procedural rules for a reviewer action.
Commit message	Descriptive rules for the body. The subject line is a title, so the sentence-length rule does not apply to it.
Error message	State the condition, then the action, then the result.
Code comment	Descriptive rules. Never change an identifier or a quoted string to satisfy a prose rule.
Agent conversational reply	Procedural rules for an instruction to the user. Descriptive rules for an explanation. Keep code, a command, and a file path unchanged.

How the Assistant Performs This Work

This section states the process the assistant uses to apply this rule.

For a structure rule, the assistant applies the rule directly. Examples are the sentence-length limit, the verb-form list, and the paragraph limit. The assistant does not need the PDF for a structure rule.

For a word-level ruling, the assistant needs the PDF of the standard. The PDF holds the one dictionary with the approved word list. Without the PDF, no other source gives an exact, correct ruling for one word.

When the PDF is present, the assistant does this process:

1. Extract the text of the PDF to a text file. The assistant uses a tool named pdftotext for this step, because a direct read of the PDF does not work.
2. Search the extracted text for the exact word.
3. Check that the result gives a clear, matched pair: the word, and its approved status or its approved replacement.
4. State the ruling only when the result is clear. A word-level ruling from a garbled or a split table row is not a clear result.

When the PDF is not present, or a result stays unclear after the search, the assistant does this instead:

1. The assistant does not state a guess as a confirmed ruling.
2. The assistant applies the general principles in this document: a plain word, a common word, one meaning for one word.
3. The assistant states the uncertainty to the user, in plain terms.
4. The assistant points the user to the official standard at asd-ste100.org, for a final, authoritative answer.

Limits of This Rule

No tool, and no assistant, can guarantee full ASD-STE100 compliance. A human writer gives the final approval on a written deliverable. For an authoritative ruling on one word, check the official standard at asd-ste100.org.

This document is an internal reference. This document is not an ASD or STEMG product, and ASD does not endorse it.