Background

With the advent of the FAIR principles for data in 2016 (Wilkinson et al. 2016), researchers and data stewards were given a clear set of aspirations for enhancing the value of their data by making them as Findable, Accessible, Interoperable, and Reusable as possible. Guidelines and other resources for the "fairification" of datasets quickly followed (“FAIR Cookbook,” n.d.). While many creators and curators of open datasets in academic, government, and not-for-profit contexts are adopting these principles, restricted data have fallen behind in being made FAIR. Restricted data, in the context of this study, are defined as data with potential value for research that are only accessible via request or application.

Restricted data for research

The category of restricted data is particularly relevant to researchers in the health sciences, who regularly require access to data measuring individual and group characteristics and outcomes that are considered sensitive in nature. A recent review of restricted health data sources in Canada by the present authors (Read et al. 2024a) found that none of the sources investigated employed standardized and machine-readable descriptive metadata of any kind, and few provided information that would adequately describe the data for even a human reader. This circumstance is decidedly un-FAIR and presents significant barriers to use for anyone not already familiar with a dataset’s existence, availability, and content. In many cases, the information provided by data sources was also not sufficient to allow a researcher to assess whether pursuing access to a dataset would be appropriate in the context of their research or their role (e.g., student vs. faculty); these issues are well documented in the literature on this topic, particularly with respect to navigating the access process for acquiring restricted health data (Bekemeier et al. 2019; Clayton et al. 2021; Hanna et al. 2021; Ho, Gorges, and Portales-Casamar 2018; Mpango and Nabukenya 2019; Pongiglione et al. 2021; Prince et al. 2018; Saulnier et al. 2019; Siu et al. 2016; Sydes et al. 2015).

Insufficient or nonexistent metadata is not an inherent characteristic of restricted access data. While datasets themselves may not be available openly, in most cases there is little need for data sources to conceal basic information that would ease the discovery of their content, and help potential users understand procedures and eligibility for access. As one study points out: "FAIR is not equal to open" (Mons et al. 2017). Rather, implementation guidelines and interpretations of the FAIR principles are agnostic as to dataset openness (Jacobsen, de Miranda Azevedo, et al. 2020; Jacobsen, Kaliyaperumal, et al. 2020), and have been applied to even very sensitive data (van der Velde et al. 2022; Ghardallou et al. 2022). A more FAIR landscape of restricted data—in health spaces and beyond—would incorporate adequate descriptive and access information in the form of structured metadata. This would allow researchers to find and evaluate restricted datasets more easily and allow systems such as data indexers and aggregators to harvest and expose these valuable resources for discovery.

To learn more about how to improve the discovery of and access to restricted data, this study explored 48 online sources of restricted health data in Canada to:

• identify what kinds of information these sources provide about datasets themselves and the procedures for accessing them;

• identify commonalities across sources to inform the creation of possible metadata elements for restricted data; and

• assess whether and to what extent these elements can be accommodated within existing metadata schemas.

This research aimed to determine gaps and opportunities in the ways that restricted data sources make their data discoverable and accessible, and in the extent to which available metadata schemas facilitate discovery and access. This manuscript was originally made available as a pre-print publication (Read et al. 2024b).

Methods

This study used an iterative, three step process to:

1. Extract dataset and access information provided by a sample of 48 restricted data sources that did not utilize structured metadata (Read et al. 2024a);

2. Identify commonalities across these data sources to develop possible metadata elements for restricted data; and

3. Map these metadata elements to existing metadata schemas to evaluate how well the latter currently accommodate information supplied by restricted data sources.

This study began in December 2021 and was completed in March 2023.

Step 1: Extract dataset and access information from restricted data sources

We examined the 48 restricted data sources from our previous study to identify the “dataset information” they provided to describe their datasets, and the “access information” they used to describe their access request processes and requirements. We reviewed each data source website as well as any documents we could download that provided information about the dataset or the actions required to access the dataset. Some data sources contained many datasets with varying levels of access, meaning the dataset and access information we extracted could appear more than once in a single data source. Because the information we found pertained to different datasets, we considered this information unique and included them as separate even though they originated from the same source. All dataset and access information from each data source was compiled into two spreadsheets, which are available for download in the supplemental files.

Dataset information

We defined “dataset information” as a discrete piece of information the data source provided about their datasets themselves (e.g., a dataset description, the date the data was collected, the dataset population). We extracted this information from 14 of the 48 data sources because they were the only sources that described their data to some extent.

Access information

We defined “access information” as a discrete piece of information the data source provided related to the access request process (e.g., who is eligible to access the data, the cost of the dataset, what documents are required when submitting an application). We extracted this information from all 48 data sources.

Step 2: Identify common dataset and access elements in restricted data sources

To identify commonalities across data sources, we manually grouped the dataset and access information together into meaningfully similar categories and recorded the frequency in which they appeared. Dataset and access information was considered “common” if it appeared more than once. We then ascribed definitions to the common categories that captured the nature of the information provided or requested; these categories became the “dataset elements” and “access elements” that we mapped to existing metadata schemas in step 3.

Step 3: Map common dataset and access elements to existing metadata schemas

Using our newfound common “dataset elements” and “access elements”, we mapped each element to the following metadata schemas to determine to what extent they aligned: DataCite (2021), DDI-Lifecycle (n.d.), DDI Codebook (n.d.), DCAT Vocabulary (2023), and DATS (Sansone et al. 2017). These metadata schemas were selected because of their focus on describing data.

We performed our mapping using an “exact”, “partial”, or “none” matching system. An “exact” match was assigned if an element we identified matched exactly to an element in a metadata schema (e.g., Dataset title = Title in the DataCite Metadata Schema). A “partial” match was assigned if an element we identified had some relation to an element in a metadata schema but did not match exactly (e.g., Data Custodian = contributorType “DataManager” in the DataCite Metadata Schema). “No match” was assigned if we could find no corresponding element in a metadata schema.

Once the mapping process was complete, we recorded which of our dataset elements and access elements had the strongest alignment with elements across multiple existing metadata schemas. We designated strong alignment when we found four or more exact matches for that element across the five schemas we examined.

Results

Dataset and access information

We extracted 275 examples of dataset information in 14 data sources, and 2,059 examples of access information in 48 data sources.

Common elements

Dataset elements

From the 275 examples of dataset information, we identified 35 common “dataset elements” which were subsequently grouped into broader categories (Table 1). Within these broader categories, Data Characteristics (n=91), Access and Availability (n=34), Description (n=33), and Provenance (n=27) represented the most common elements identified across data sources. These commonalities indicate that the restricted data sources in our sample provided similar information about their datasets.

Table 1: Frequency of restricted dataset element commonalities across data sources

Access elements

From the 2,059 examples of access information we extracted, we identified 27 common “access elements” which are categorized and listed in Table 2. This categorization identified strong commonalities between access elements for Request Requirements, in particular Research Team Information (n=668), Research Plan (n=374), Data Management (n=215), Description of Request (n=184), and Ethics Approval (n=151). These findings indicate that the restricted data sources in our sample provided similar information with respect to their data access request processes and requirements.

Table 2: Frequency of restricted access elements commonalities across data sources

Mapping elements to metadata schemas

Mapping dataset elements

When mapping our common dataset elements to existing metadata schemas, we found that there was relatively strong alignment between the information our 48 restricted data sources provided and the information that metadata schemas already capture (Figure 1). Notably, the DDI Lifecycle and DDI Codebook metadata schemas had very strong alignment with our common dataset elements, for which we assigned 91.4% and 85.7% “exact” matches, respectively. The DATS (40%) and DataCite (37.1%) metadata schemas received the fewest “exact” matches. Metadata schemas that received the most “no match” equivalents included DataCite (34.3%), DCAT (20%), and DATS (14.3%).Figure 1: Dataset elements alignment with existing metadata schemas

The dataset elements that demonstrated the strongest alignment across metadata schemas (>=4 schemas) were:

• Dataset title

• File type and format

• Keyword

• Additional information

• Classifications

• Record identifier

• Size of dataset

• Publications

• Legal, licensing, security considerations

• Study title

• Study identifier

These results indicate that the restricted data sources in our sample tended to capture information about their datasets that align with existing metadata schemas.

Mapping access elements

Although the 48 restricted data sources in our sample described their access procedures in similar ways, our attempt to map the common access elements we identified to existing metadata schemas was unsuccessful because no schemas accommodated the level of detail used across sources. While existing schemas include elements such as accessRights, accessRestrictions, accessConditions, and licenceInformation, our restricted data sources employ much more granular concepts when describing access processes and requirements (Table 2). Our inability to map the common access elements to any of the metadata schemas we selected suggests that these schemas are not currently suited to capturing information about access and request processes for restricted data.

Discussion

Our results suggest that the descriptive dataset information provided by restricted data sources, even where minimal, could be accommodated by an existing metadata schema, while information about access requirements and procedures could not. In practice, this means that it would be possible for many restricted health data sources to adopt an existing metadata schema, while metadata standards bodies could take action to better accommodate the access information that restricted data sources provide. If undertaken, these efforts could significantly improve the FAIR-ness of restricted access datasets by making them more findable and accessible.

Improving restricted data discovery

However, because none of these data sources utilize structured metadata, at present their discoverability is limited. Researchers locate data through prior awareness (either personally or via others), a search engine or data aggregator (e.g., Google Dataset Search, HealthData.gov, the European Data Portal, and Canada’s Lunaris), or a data support professional such as a librarian (who would similarly rely on existing knowledge, searching, and data discovery infrastructure) (Krämer et al. 2021; Koesten et al. 2017). Because the data sources in this study did not make use of structured metadata, at present their “visibility” to search engines and aggregators is, respectively, limited or non-existent. Many of the data sources in our study shared commonalities in the ways of how they described their datasets, and these commonalities align well with existing metadata schemas. If the data sources in this study—and restricted data sources generally—were to take advantage of their “metadata readiness” by adopting an existing metadata schema, it would significantly enhance researchers’ ability to find them using modern discovery infrastructure.

For restricted data sources to adopt metadata standards, data stewards will need an understanding of metadata and its value, and the resources necessary to adopt and implement it. This may include an understanding of how difficult it is to find their datasets currently, why metadata improves discoverability, how to apply a metadata standard to their data, and where their datasets will be findable once that is achieved. It may also include financial or human resources. Many of the data sources we identified in this study represented small, one-time projects that presumably do not have large teams of personnel to take on this task. If national funding bodies or data initiatives are interested in improving the discovery of restricted data sources, we recommend that they incentivize, support, and help implement the adoption of metadata among restricted data sources. For example, because of this work, the Digital Research Alliance of Canada (Alliance) is developing a strategy to work with data sources included in this study to adopt a metadata schema, with the goal of making them findable in Canada’s data discovery index, Lunaris leveraging its Network of Experts (Digital Research Alliance of Canada 2022b). Organizations and initiatives in other geographical or disciplinary contexts could offer similar support to restricted data sources in their areas.

While the adoption of metadata standards by sources will be an important step toward improving the discovery of restricted data, additional challenges remain. To date, restricted data is generally not registered with a persistent identifier such as a DOI or handle. However, because any prospective restricted metadata record would not be a direct access point to the data itself, the potential utility of such a practice for improving data discovery is not always clear to data stewards. Greater awareness is needed of the utility of persistent identifiers—and, their accompanying open metadata, which is widely used by data aggregators—for improving the discovery of restricted data. Future directions for this research should consider both the discovery of restricted data and the preservation of that data for the long term. Questions we posit include: what are the recommended practices for assigning DOIs to open metadata records for restricted datasets?; and is it feasible to create national infrastructure that can reliably make restricted datasets discoverable in one location but maintain its security and preservation in another? One emerging initiative attempting to address these issues is the Alliance’s Controlled Access Management project, which aims to enable researchers, institutions and repositories to manage controlled access to research data through new software, tools and workflows (Digital Research Alliance of Canada 2022a).

Improving restricted data access

While adding descriptive dataset metadata to restricted data sources will make data more findable, the accessibility of these datasets could be significantly improved by structured metadata capturing information and requirements related to data access (“access metadata”). The widespread adoption of access metadata for restricted data would help researchers understand, at a glance, whether a particular dataset is worth pursuing (e.g., timeline to access, eligibility requirements, access requirements, cost). Within our sample, access information was presented inconsistently and in an unstructured way (if at all) or was only presented during the request process itself (e.g., while populating and clicking through a multi-step application) (Read et al. 2024a). Ideally, when a researcher examines a dataset record in a repository, catalog, or index, they would be able to understand not only its contents and characteristics, but also the restrictions, procedures, and conditions for use (Figure 2). Access metadata could also be used from a search perspective to help researchers filter for datasets for which access will be achievable in their particular context. For example, a graduate student seeking health data that was free of charge and which they could access within two months could quickly identify datasets that satisfy these criteria.

Figure 2: Mock restricted data record with access metadata

At present, metadata schemas do not accommodate the level of detail restricted data sources commonly provide about access procedures and requirements, instead typically providing one free-text element to capture all related information (e.g., accessRights, accessRestrictions). With only one metadata element devoted to access, restricted data sources lack a template for providing the types of information important to researchers when evaluating a dataset for use. Additionally, this single-element approach precludes the ability of access characteristics to be filtered in discovery infrastructure. To improve the availability, findability, and clarity of access-level details for researchers, we strongly recommend that metadata standards bodies expand their schemas to accommodate more detail about dataset access, in alignment with the elements identified in this study. While metadata schemas do not currently accommodate restricted data sources, we acknowledge that libraries have developed data catalogues with custom access metadata as a stopgap to help researchers locate restricted data (Yee et al. 2023).

Future directions

This study examined dataset and access information supplied by restricted health data sources that are stewarded by academic, government, and non-profit organizations in the Canadian context. We believe that our findings can inform efforts to develop access-specific extensions to existing metadata schemas, where the commonalities identified in this study could serve as the basis for new metadata elements. The addition of access-specific metadata to existing schemas could then support existing data repository infrastructure to ensure that restricted data can be discoverable and that the access process is transparent. Data catalogues and indices could then also aggregate restricted datasets alongside those that are made public. Finally, adding access metadata to existing standards can support individual researchers who are collecting restricted data and are required to comply with emerging funder and publisher data sharing policies. These researchers would benefit from clear and consistent restricted access metadata standards, which could allow them to make their research data more discoverable and accessible either via a repository, a publication data availability statement, or institutional/organizational data source.

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