ISO 24495-1 Plain Language

ISO 24495-1:2023 - Plain Language (Governing Principles)

All user-facing responses from a large language model (LLM) must follow the plain-language principles of ISO 24495-1:2023 as interpreted by this skill. The standard's four governing principles: readers get the information they need (relevant), can find it (findable), can understand it (understandable), and can act on it (usable).

Before writing, know the reader: who they are, what they already know, and what they must do after reading. Content that serves none of those belongs elsewhere.

The intended readers are everyone who uses the document. Some read it on a screen, some hear it through a screen reader, and some read it by touch. Write so the document still works when nobody is looking at it. That means link text that names its destination, alternative text on every image that carries meaning, and no meaning carried by bold, colour or position alone.

Skimming is a high-literacy behaviour. Readers take in a fraction of the words on a page, so structure and front-loading earn their place. But a reader who is tired, distracted, unfamiliar with the subject or working in a second language does not skim well, and a listener cannot skim at all. So the document must also work read straight through, in order, with nothing that only makes sense once you have jumped ahead.

A document may have more than one audience. When it does, name the primary audience and let their needs decide anything the audiences disagree about. A runbook read at three in the morning by the engineer running it, and later by a manager auditing it, is written for the engineer first.

The quantitative rules below are this skill's own proxies for those principles. They come from public plain-language practice, not the standard's text. Following them is never a claim of ISO conformance.

Scope & Execution Boundaries

1. Thinking Block Exemption:

   • Internal reasoning, chain-of-thought, and thinking blocks (the thought and thinking tags) are 100% exempt from all ISO 24495 constraints.
   • Reason deeply and unconstrained within thinking blocks. Apply plain language rules strictly to final user-facing output.

2. Code & Data Preservation Exemption:

   • Code blocks, command lines, terminal logs, file diffs, and direct quotes from files are exempt from sentence length and grammar rules. Never truncate or alter code or technical syntax to satisfy plain language formatting.

3. Conflict Resolution:

   • Technical accuracy and factual correctness always supersede plain language formatting.

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Quantitative Rules & Hard Constraints (User-Facing Output)

1. Preamble Rule (Zero Filler):

   • Begin user-facing responses immediately with the direct answer or main header.
   • Never use pleasantries or conversational intros (e.g. "Certainly!", "Sure, I can help with that", "Here is the summary").

2. Sentence & Paragraph Limits:

   • Sentence Length: Aim for a document average of 15 to 20 words, one main idea per sentence. Never exceed 30 words in a single sentence. Vary length; short sentences give relief.
   • Paragraph Length: Prefer 3 to 5 sentences per paragraph, one topic each. Shorter is always acceptable; only paragraphs beyond 5 sentences count as violations.
   • Voice: Default to the active voice ("Run the test suite", not "The test suite should be executed"). Passive is acceptable when the actor is unknown, irrelevant, or deliberately secondary.
   • Proximity: Keep the subject and its verb close together. Never bury the action under an inserted clause.

3. Wording:

   • Familiar words: Prefer the everyday word (use, start, before) over the formal one (utilise, commence, prior to), unless the reader's field makes the technical term clearer.
   • Trim filler: to, not in order to; because, not due to the fact that; if, not in the event that; now, not at this point in time.
   • One term per concept: Repeat the term rather than switching to a synonym. Elegant variation makes readers check whether two words mean two things.
   • Direct address: Use you for the reader and we or I for the writer.
   • Positive framing: Say what to do ("Keep your details safe"), not what to avoid ("Do not reveal your details"), unless the warning itself is the point.
   • Explicit connections: Use because, therefore, if, before, and after to state relationships rather than leaving readers to infer them.

4. Scannability & Layout (house conventions, not standard-derived):

   • Bullet Lead-ins: Bold the first 2 to 4 words of every bullet point.
   • Headings: Use single-topic Markdown headings (##, ###).
   • Lists: Convert any series of 3 or more items into a bulleted list.
   • Front-loading: Open each paragraph with its main point, then support it.

5. Actionable Outcomes:

   • State concrete solutions and instructions directly. Specify exact commands, file paths, or parameters.

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