ONP-3500

Open News Protocol (ONP): Accessibility

Abstract

This document defines the Accessibility Extension: org.onp.accessibility, fulfilling the promise ONP-2200 Section 4.5 made when it kept alt_text deliberately minimal and deferred richer accessibility metadata here. Rather than embedding alternative content (transcripts, captions, audio descriptions, plain-language rewrites) directly as new field values, this Extension points to them as properly-typed, independently verifiable Companion Objects — an Article for a transcript or plain-language version, a Media Object for captions or an audio-described video — reusing the existing Companion machinery rather than introducing a second, unverified way to carry the same kinds of content. With this document, every Companion and Extension named in ONP-0000's original roadmap (0000-3500) is published.

Status of This Document

This document is part of the ONP Extension series (ONP-3000-3999) and completes the original Extension roadmap (ONP-0000 Section 4.1). It is directly implementable. It is a Working Draft.

Normative Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174], per the interpretation established in ONP-0000.

1. Introduction

ONP-2200 Section 4.5 gave Media a baseline alt_text field and explicitly deferred anything richer to this document, to avoid raising Media's own required-effort bar (Principle P2) while still acknowledging that a single short string cannot serve every accessibility need — a complex chart needs a longer description than a photograph does; a video needs captions and, separately, an audio-described version; an article MAY benefit from a plain-language alternative for readers with cognitive disabilities or those reading in a non-native language. This document supplies those, each as a pointer to a properly-typed Object rather than a new, informally- structured field.

2. Scope

2.1 In Scope

• long_description, transcript_ref, captions_ref, audio_description_ref, reading_level, and plain_language_ref;
• the design choice to represent alternative content as Object References to Media or Article Companion Objects, not as inline, unverified strings or URLs;
• the one Claim Domain this Extension declares, and its declared dependency on the Article and Media Companions.

2.2 Out of Scope

This document does NOT define:

• alt_text itself — remains owned by ONP-2200 Section 4.5;
• any specific captioning file format, transcript formatting convention, or readability scoring algorithm — this document points to where such content lives, it does not standardize the content's own internal format;
• any rendering or assistive-technology implementation detail.

3. Terminology

This document introduces no new general terms beyond its namespace and Claim Domain registration (Section 4).

4. Requirements

4.1 Extension Namespace Declaration

This Extension's fields MUST be carried under onp:extensions.org.onp.accessibility.

4.2 Companion-vs-Extension Classification

Does "Accessibility" have independent identity and an independent
lifecycle, separable from the Object it describes?

- Accessibility metadata is inherently a property of, or a set of
  pointers from, an existing Object; it has no standalone existence
  a reader would reference on its own.
- NO -> Extension, consistent with every other Extension published
  in this series.

4.3 Companion Dependency Declaration

Per ONP-3000 Section 4.2, rule 4, this Extension declares a dependency on two Companions: ONP-2100 (Article), the target of transcript_ref and plain_language_ref, and ONP-2200 (Media), the target of captions_ref and audio_description_ref. It does not depend on any other Companion.

4.4 Content Schema

long_description, transcript_ref, captions_ref, audio_description_ref, reading_level, and plain_language_ref are all OPTIONAL, under the single Claim Domain accessibility-alternatives (Section 4.9).

4.5 Long Description

long_description, if present, MUST be a string: an extended description for content too complex for a short alt_text alone (a chart, an infographic, a complex diagram) — supplementary to, not a replacement for, alt_text (ONP-2200 Section 4.5).

4.6 Transcript and Captions

1. transcript_ref, if present, MUST be an Object Reference (OID form) to an Article Companion Object (ONP-2100) containing the full text transcript of audio or video content.
2. captions_ref, if present, MUST be an Object Reference (OID form) to a Media Companion Object (ONP-2200) whose asset_url locates a timed captions/subtitles file, verifiable via that Companion's Verified Asset Reference pattern (ONP-2200 Section 4.4).
3. audio_description_ref, if present, MUST be an Object Reference (OID form) to a Media Companion Object representing an alternate, audio-described version of a video, for users who cannot see its visual content.

4.7 Reading Level

reading_level, if present, MUST be a string identifying an established, existing readability metric and its value (e.g. a Flesch-Kincaid grade level) rather than a newly-invented scale, consistent with Principle P3.

4.8 Plain-Language Reference

plain_language_ref, if present, MUST be an Object Reference (OID form) to a separate Article Companion Object containing a plain-language version of the same story, for readers with cognitive disabilities or those who benefit from simplified text. It MUST NOT be treated as a correction (ONP-2700) or a new Version in the original Article's own lineage (ONP-0006) — it is a parallel, independently existing Object, not a supersession.

4.9 Claim Domain

This Extension declares one Claim Domain: accessibility-alternatives, covering all six fields in Section 4.4. It MUST be registered in ONP-0002 alongside this document's publication (Section 10.3).

5. Object Model

{
  "onp:extensions": {
    "org.onp.accessibility": {
      "long_description": "string, OPTIONAL",
      "transcript_ref": "onp:oid:..., OPTIONAL — Article Object",
      "captions_ref": "onp:oid:..., OPTIONAL — Media Object",
      "audio_description_ref": "onp:oid:..., OPTIONAL — Media Object",
      "reading_level": "string, OPTIONAL",
      "plain_language_ref": "onp:oid:..., OPTIONAL — Article Object"
    }
  }
}

6. Processing Model

6.1 Consumption

An assistive technology or accessibility-aware Node MAY resolve transcript_ref, captions_ref, audio_description_ref, or plain_language_ref using the standard Object Reference resolution procedure (ONP-2000 Section 6.2), then process the resolved Object through its own Companion (ONP-2100 or ONP-2200) exactly as it would for any other Article or Media Object — no new resolution logic is required beyond what those Companions already define.

6.2 Interoperability

A Node without this Extension implemented simply does not see accessibility alternatives; the base Object (with its alt_text, if any) remains fully usable regardless. This Extension is not Companion-agnostic in the same sense as ONP-3100 through ONP-3400 — it explicitly depends on Article and Media (Section 4.3) — but it does not require both to be present simultaneously; a publisher MAY populate only the fields relevant to a given Object's own content type.

7. Examples

7.1 A Video with Captions and Audio Description

{
  "onp:extensions": {
    "org.onp.accessibility": {
      "captions_ref": "onp:oid:regiopurmerend.nl:ondertiteling-fusie-bijeenkomst",
      "audio_description_ref": "onp:oid:regiopurmerend.nl:audiodescriptie-fusie-bijeenkomst",
      "transcript_ref": "onp:oid:regiopurmerend.nl:transcript-fusie-bijeenkomst"
    }
  }
}

7.2 A Plain-Language Version of an Article

{
  "onp:extensions": {
    "org.onp.accessibility": {
      "reading_level": "Flesch-Kincaid grade 6",
      "plain_language_ref": "onp:oid:regiopurmerend.nl:fusie-onderzoek-eenvoudig"
    }
  }
}

The original Article keeps its own reading level implicitly higher; plain_language_ref points to a genuinely separate, independently signed Article Object with its own OID — not a Version in the same lineage.

8. Security Considerations

Every reference field in this Extension resolves through the standard Object Reference mechanism (ONP-2000 Section 6.2) and is therefore subject to the same non-blocking, independently-verified resolution rules as any other reference in this series: an unreachable transcript_ref does not affect the base Object's own Core validity, and a resolved target is verified through its own Companion's ordinary Core validation, not granted any special trust for being accessibility-related content.

9. Privacy Considerations

This document defines no fields carrying personal data directly. Where a transcript_ref or captions_ref target contains spoken content naming or otherwise identifying individuals, the referenced Article or Media Object's own privacy considerations apply — this Extension introduces no additional privacy mechanism beyond pointing to that content.

10. References

10.1 Normative References

• [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119.
• [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174.
• ONP-0001, Architecture — Section 4.4, the decision test applied in Section 4.2.
• ONP-0003, Design Principles — Principle P2 (Minimal Required Surface, Section 1) and Principle P3 (Ordinary Technology, Section 4.7).
• ONP-2000, Companion Framework — Section 4.3 (Object Reference mechanism), Section 6.2 (resolution procedure, reused in Section 6.1).
• ONP-2100, Article; ONP-2200, Media — the Companions this Extension declares a dependency on (Section 4.3) and points into throughout.
• ONP-2700, Corrections — the boundary Section 4.8 draws against, clarifying plain_language_ref is not a correction.
• ONP-3000, Extension Framework — Section 4.1 (namespace registration), Section 4.2, rule 4 (Companion dependency declaration), Section 4.3 (Claim Domain declaration).

10.2 Informative References

• None beyond the normative set.

10.3 Registry Registration

As part of this document's publication, org.onp.accessibility and accessibility-alternatives are registered in ONP-0002.

Appendix A: Full Schema Reference

{
  "onp:extensions": {
    "org.onp.accessibility": {
      "long_description": "string, OPTIONAL",
      "transcript_ref": "string (OID), OPTIONAL",
      "captions_ref": "string (OID), OPTIONAL",
      "audio_description_ref": "string (OID), OPTIONAL",
      "reading_level": "string, OPTIONAL",
      "plain_language_ref": "string (OID), OPTIONAL"
    }
  }
}

Appendix B: Accessibility Extension Checklist

[ ] Fields carried under onp:extensions.org.onp.accessibility
[ ] transcript_ref and plain_language_ref, if present, point to
    Article Objects (ONP-2100), not Media Objects
[ ] captions_ref and audio_description_ref, if present, point to
    Media Objects (ONP-2200), not Article Objects
[ ] plain_language_ref target is a separate Object with its own
    OID, not a Version in the original Article's own lineage
[ ] alt_text itself remains defined on the Media Object per
    ONP-2200 — not redefined here

End of Document