Area VI

Controlled Natural Languages & Constrained Registers

Engineered subsets of English

A controlled natural language trades expressive freedom for guarantees. Fix the dictionary, ban the passive, assign one meaning to each word, and ambiguity has nowhere to hide. Aerospace technicians, standards authors, and knowledge engineers have spent decades refining these subsets; they translate almost directly into instructions a language model can honor and a reviewer can audit.

1. Simplified Technical English (ASD-STE100) The aerospace CNL

   Restrict prose to an approved dictionary and strict grammar rules built for procedures.

2. Basic English & Restricted Lexicons Writing to a fixed word list

   Constrain the vocabulary to a small approved list, forcing plain, universal phrasing.

3. Attempto Controlled English (ACE) Prose that parses to logic

   Write in a subset so precise it maps unambiguously onto formal first-order logic.

4. RFC-2119 Normative Keywords MUST · SHOULD · MAY

   Reserve specific capitalized keywords for exact, agreed levels of requirement.

5. Structured Topic Typing (DITA) Concept · Task · Reference

   Force each unit of content into one topic type instead of mixing modes.