Table 4 List of 13 FAIRness maturity indicators evaluated in this study, based on the framework proposed by Wilkinson et al. [6, 12]

Indicator identifier

Indicator name

Indicator description

F1.1

Identifier uniqueness

Whether there is a scheme to uniquely identify the digital resource

0: Indicator is not met

2: Indicator is met

F1.2

Identifier persistence

Whether there is a policy or scheme which ensures the persistence of the digital resource identifier

0: Indicator is not met

2: Indicator is met

F2

Data are described with metadata

Whether metadata corresponding to the digital resource are available

0: Indicator is not met

2: Indicator is met

F3

Resource identifier in metadata

Whether the metadata contains the unique identifier for the digital resource

0: Indicator is not met

2: Indicator is met

F4

Indexed in a searchable resource

Whether the digital resource can be found by web-based search engines using search terms such as title, author or key words. Google Search was used in this assessment

0: Indicator is not met

2: Indicator is met

A1

Access protocol

Whether there is an open and free access protocol to retrieve the digital resource, and if not, whether the specifications to access restricted content are provided

0: Indicator is not met

2: Indicator is met

A2

Metadata longevity

Whether there is a policy to guarantee the persistence of metadata even in the case of absence or removal of the digital resource itself

0: Indicator is not met

2: Indicator is met

I1

Use a knowledge representation language

Whether a formal language for knowledge representation is used in the digital resource. This indicator was assessed in terms of the format of the data.

0: Indicator is not met

1: Indicator is partially met when the resource is in a structured, non-proprietary, editable format (e.g., CSV, XML)

2: Indicator is met when the language used is cited and documented

I2

Use of FAIR vocabularies

Whether the digital resource uses formal and shared vocabularies (ontologies) for knowledge representation, which are themselves terms from open, community-accepted vocabularies published in an appropriate knowledge-exchange format.

0: Indicator is not met

1: Indicator is partially met when the vocabularies used in the resource are documented

2: Indicator is met

I3

Use of qualified references

Whether the digital resource or its metadata contain relationships with third-party data, with an explicit and useful semantic meaning

0: Indicator is not met

2: Indicator is met

R1.1

Accessible usage license

Whether there is a license document for the digital resource and the ability to retrieve those documents

0: Indicator is not met

1: Indicator is partially met when elements concerning the conditions for re-use, copying or distributing the resource are available but no formal license can be found

2: Indicator is met

R1.2

Detailed provenance

Whether the digital resource content is associated with provenance information associated with the data, covering at least: (i) who produced the data and when, and (ii) why and how the data was produced (context and relevance of the data). The availability of such information in the digital resource itself or its metadata was evaluated, not in the content of the associated article

0: Indicator is not met

2: Indicator is met

R1.3

Meet community standards

Whether the digital resource is listed by a recognized body as meeting community standards. Repositories were considered as compliant when listed by FAIRsharing, the Registry of Research Data Repositories or Core Trust Seal (www.coretrustseal.org)

0: Indicator is not met

2: Indicator is met