Table 1 Description for each maturity indicator of how the ERM is FAIR and how it can be used to make nanosafety data FAIR

Findability

F1. (Meta)data are assigned a globally unique and persistent identifier

The registry is released to Zenodo, which provides it with a DOI

The ERM identifier is a globally unique and persistent identifier; The registry supports depositing metadata

F2. Data are described with rich metadata (defined by R1 below)

The ERM identifier is registered with FAIRSharing at fairsharing.org/bsg-s001384/, in identifiers.org at registry.identifiers.org/registry/erm (MIR:00,000,763), and in Bioregistry at bioregistry.io/registry/erm

The ERM is one important aspect of rich metadata and helps make metadata findable across resources

F3. Metadata clearly and explicitly include the identifier of the data they describe

The registry archive uses the DOI to point to that version of the registry content

The ERM identifier can easily be included in spreadsheets and as Compact Identifiers in reports

F4. (Meta)data are registered or indexed in a searchable resource

Zenodo records and DOIs are indexed by many services

Some metadata can be shared in the registry, but with the ERM identifier further metadata can also be provided via other channels

Accessibility

A1. (Meta)data are retrievable by their identifier using a standardised communications protocol

GitHub and Zenodo use HTTP

A2. Metadata are accessible, even when the data are no longer available

Zenodo guarantees availability for 20 years

Interoperability

I1. (Meta)data use a formal, accessible, shared, and broadly applicable language for knowledge representation

The registry uses the RDF specification and all instances are annotated with ontologies

ERM identifiers are URIs and can be expressed as Compact Identifiers

I2. (Meta)data use vocabularies that follow FAIR principles

The ERM is FAIR and by using it, users implement I2

I3. (Meta)data include qualified references to other (meta)data

The registry explicitly encourages users to link to other resources, including webpages and projects

The global unique ERM identifier enables linking (meta)data

Reusability

R1. Meta(data) are richly described with a plurality of accurate and relevant attributes

The registry is available under a CCZero license. The ERM identifiers specification is documented on GitHub and archived on Zenodo

By adding the global unique ERM identifier to research output, reuse is facilitated. The ERM identifiers simplify tracking the provenance of nanomaterials and their properties