# LuaBill validation-rule overlay

This directory supplements the original, unchanged Mustang CLI 2.26.0 JAR with
official EN 16931 CII 1.3.17 and XRechnung CII Schematron 2.6.0 resources.
`manifest.json` records the release URLs, source archives, versions and SHA-256
of every distributed file. The original source ZIPs and upstream licenses are
included alongside the runtime files.

The original EN 16931 XSLT is used unchanged. The original XRechnung XSLT is
also unchanged, at
`overrides/xslt/XR_30/official-xrechnung-2.6.0.xsl`.

## Mustang SVRL compatibility adapter

The entry point `overrides/xslt/XR_30/XRechnung-CII-validation.xslt` is a small
LuaBill compatibility adapter, Copyright 2026 Vsevolod Shashkov & Mikhail
Shashkov, licensed under Apache License 2.0 (the LuaBill distribution's
`LICENSE`). It imports and executes the original official XRechnung XSLT, then
copies its SVRL validation report, omitting only `svrl:metadata` elements.

SchXslt 1.10.1 adds this informational compiler metadata to the report, while
the JAXB SVRL reader in Mustang 2.26.0 does not recognize it. The adapter does
not change any official rule, assertion, test expression, severity, location,
diagnostic or validation message. It removes no `failed-assert`,
`successful-report`, `active-pattern` or `fired-rule` elements.

This is a LuaBill rule overlay, not a modified or newly released Mustang JAR,
and not the independent KoSIT validator-configuration package.

## Third-party sources

- EN 16931 validation artefacts 1.3.17, ConnectingEurope/eInvoicing-EN16931:
  EUPL-1.2. Original license: `licenses/LICENSE-EN16931.txt`.
- XRechnung Schematron 2.6.0, KoSIT/itplr-kosit: Apache-2.0. Original license:
  `licenses/LICENSE-XRechnung.txt`.
- SchXslt 1.10.1, Copyright (c) 2018-2021 David Maus: MIT. Its generated
  support code is present in the official XRechnung stylesheet; the original
  license is `licenses/LICENSE-SchXslt.txt`.

Original upstream README files are retained in `attribution/`.