License Clarity

Machine-readable license identifier (SPDX)

Access (A)

Reusable (R1.1)

Justification

A machine-readable license is Essential per RDA (RDA-R1.1-01M). Without a license, data is legally unusable. DataCite includes Rights. Dublin Core includes Rights as a core element. schema.org includes license as recommended. Four sources converge.

Practical Guide

must-have

Add a license. 11.3x citation lift — unlicensed data is legally unusable.

A machine-readable license isn't just good practice — it's legally necessary. Data without a license is copyrighted by default, making it unusable. Datasets with SPDX licenses receive 11.3x more citations (RR = 11.32, p < 0.001). The 2.1% of Zenodo datasets without licenses receive almost no citations. The RDA rates this as Essential priority.

For Repositories

Make license selection required during deposit
Provide a curated list of SPDX-compatible licenses
Default to CC-BY-4.0 or CC0 if the depositor doesn't choose

For Depositors

Always select a license — unlicensed data is legally unusable
Prefer CC0 (public domain) or CC-BY-4.0 for maximum reuse
If your funder requires a specific license, check before depositing

Second strongest positive signal (11.3x lift). Essential RDA priority. Legal prerequisite for reuse.

Standards Sources

Convergence score: 4/4 independent sources —

Strongly justified

Standard	Field / Property	Obligation Level
DataCite 4.6	#16 Rights	Optional
Dublin Core	Rights	Core Element
schema.org	license	Recommended
RDA FAIR	RDA-R1.1-01M	Essential

FAIR Principle Alignment

Primary mapping: Reusable (R1.1)

R1.1: (Meta)data are released with a clear and accessible data usage license

RDA FAIR Data Maturity Model Indicators:

RDA-R1.1-01M: Metadata includes information about the licence under which the data can be reused

How This Signal Is Measured

Presence of SPDX license identifier or license URL. Binary: machine-readable license present or absent.

Empirical Evidence (Zenodo, n=1.3M)

Per-signal statistics use Zenodo as the primary validation source because it is the largest general-purpose repository with structured DataCite metadata, natural variance across all 25 signals, and available citation/usage data. Domain-specific repositories exhibit ceiling effects or restricted variance that preclude per-signal discrimination. Cross-repository validation is reported separately.

Prevalence

97.9%

of Zenodo datasets

Citation Lift

11.5x

vs. datasets without

Data Source

Zenodo (CERN)

1,328,100 records analyzed

Interpretation: Near-universal on Zenodo with strong lift. The 2.1% without licenses receive almost no citations — confirming that license clarity is essential for reuse.