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Akoma Ntoso

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# Akoma Ntoso

**In short:** Akoma Ntoso structures the text of the law; Arxo executes a
model of it. There is no execution comparison here by design — only markup
and transfer. This page is for publishers and tool builders who move
between marked-up acts and pinned sources.

## What Akoma Ntoso is for

Akoma Ntoso (OASIS LegalDocML) is an XML vocabulary for acts and their
editions: work, expression, and manifestation levels with mandatory naming,
element addressing, lifecycle and temporal groups, and point-in-time URLs
for edition slices. Its strengths are maturity as a versioned standard,
edition machinery publishers actually serve (structured official text with
retrievable slices), and open parsing and publishing tooling.

## Where it meets Arxo

The intersection is markup and transfer only: marked document, edition,
and fragment against Arxo's source, edition, publication, and fragment
records. The honestly comparable property is round-trip preservability —
marked text to pinned bytes to anchors and back — with the publisher's
pinned bytes as arbiter. Amendment semantics and computed output are the
canon's job, explicitly not the markup's.

## Key differences

- **Structure is not a rule language.** The standard's own position, as
  recorded in the study, is that its XML tree is not a canonical rule
  representation. Asking it to decide cases miscasts the format.
- **Pinning granularity differs.** Arxo pins section-level editions with
  validity dates and content hashes; the markup versions whole documents
  with validity starts and regeneration records. Different granularities,
  not defects.
- **Addressing needs a mapping table.** Element identifiers map to article
  locators only through an explicit table — a naive prefix rule fails by
  construction, as the protocol's control case demonstrates. The table is
  part of the comparison, not an afterthought.
- **Exchange gaps are publisher decisions, not standard limits.** Nearly
  every sharp question in the study — vendor extensions, temporal-group
  counts across slices, elements missing identifiers, regeneration versus
  retrieval timestamps — turned out to be a property of the publisher's
  output. The page attributes them there, never to the standard.

## A concrete scenario

The prepared experiment round-trips section pins of a limitation act —
share of fragments with found identifiers, exact identifier-to-locator
matches, revision preservation across validity dates — plus four edits: a
dated slice against the current one including a visible later amendment,
whole-act versus section serialization, naive versus table mapping, and a
schema-copy control. Converter behavior was never run and is not claimed.

## Choosing and combining

Choose Akoma Ntoso when the deliverable is structured official text with
addressable editions that other tools can consume. Look to Arxo when the
text must additionally execute with dated editions and replayable
derivations. Combined, marked-up publications feed pinned sources, and
pinned sources anchor executable models — with the mapping table and byte
hashes as the joints.

## Evidence and open questions

- Sources checked: September 2026 (the vocabulary and naming-convention
  standards, the frozen schema copy, the publisher's act bytes read in
  full with verified hashes, and a European formex reference).
- Studied profile: Akoma Ntoso 1.0 with the XML schema third-edition
  copy; one publisher's output as the live exhibit.
- Basis: confirmed by documentation and byte reading plus a prepared
  protocol with frozen inputs; comparative run not performed — and no
  executable Arxo query exists for the identifier check, honestly marked
  as no model rather than stretched.
- Open: publisher-side classes above, one containment question that
  resolved as a normal outcome, and the run itself.

## Sources and reproducible materials

- Vocabulary and naming convention:
  [akn-core-v1.0-os-part1-vocabulary.html](https://docs.oasis-open.org/legaldocml/akn-core/v1.0/os/part1-vocabulary/akn-core-v1.0-os-part1-vocabulary.html)
- Publisher exhibit (official act bytes):
  [legislation.gov.uk/ukpga/1980/58/data.akn](https://www.legislation.gov.uk/ukpga/1980/58/data.akn)