NISO Access and License Indicators (ALI)

NISO Access and License Indicators (ALI) is a NISO Recommended Practice — NISO RP-22-2021, a 2021 revision of the original RP-22-2015 — that defines a small set of metadata elements for indicating whether a piece of content is free to read and what license governs its reuse. The point is narrow and deliberate: ALI does not create new licensing terms or a new access model. It defines the tags that let a system read off an existing access/license status, the same way a DOI lets a system resolve a citation without a human typing a URL by hand.

The two core elements are <ali:free_to_read>, an access indicator separate from licensing that can carry optional start_date/end_date attributes for time-limited or moving-wall access, and <ali:license_ref>, a URI pointing to the actual license terms (a Creative Commons deed, a publisher’s own terms, or any other reference). The 2021 revision added an applies_to attribute so the same article can carry different license references for different versions or uses — Crossref’s implementation, for example, recognizes values including vor (version of record), am (accepted manuscript), tdm (text and data mining), and stm-asf (the STM Article Sharing Framework). A publisher can therefore assert one license for the version of record and a more permissive one for text-and-data-mining use of the same article, machine-readably, in a single metadata record.

Why this exists

Prose license statements on a webpage are readable by people but not reliably actionable by software. ALI exists so that repositories, aggregators, CrossMark displays, discovery layers, and text-and-data-mining tools can answer “can I access and reuse this, and under what terms” programmatically, at scale, across millions of articles, instead of every downstream system scraping and interpreting license sentences that vary in wording from publisher to publisher. This is the same rationale behind persistent identifiers generally: move a determination that used to require human judgement into a structured field a machine can act on.

Where it lives

ALI’s elements are formally integrated into the JATS Tag Library (the ali: namespace, alongside ali:license_ref), which is how the elements get embedded directly in a publisher’s or archive’s article XML. Crossref added free_to_read and license_ref to its own metadata deposit schema, and its documentation notes that license information may be included with CrossMark metadata where applicable — so the same access/license status that triggers a CrossMark update check can also be read by a client as structured rights information, not just prose.

How this connects to CASRAI’s own vocabulary

ALI is the encoding layer for concepts CASRAI’s Dictionary already defines on their own terms: reuse license and licence describe what a license grants; ali:license_ref is how that grant gets pointed to in a metadata record a machine can consume. Likewise, embargo describes a time-limited access restriction; ali:free_to_read‘s start_date/end_date attributes are how that restriction gets expressed so an aggregator can compute current status without a manual check. CASRAI’s guide on Creative Commons licenses for research data covers which CC license to choose and why (CC0 vs. CC-BY vs. CC-BY-NC, and why the Open Definition doesn’t recognize CC-BY-NC as conformant) — ALI is the separate, complementary question of how that choice, once made, gets encoded so publishing and repository systems can act on it automatically rather than requiring a human to re-read the license each time. The applies_to attribute’s version-scoping also connects directly to CASRAI’s Version of record (VoR) entry, since a publisher can license the VoR and the accepted manuscript differently under the same DOI.