3. Methodology

This section outlines the REA methodology, including the search strategy, inclusion and exclusion criteria, screening, extraction, and synthesis processes. This approach yielded 42 studies, deemed sufficient given the timeframe. A detailed search protocol is available in Appendix 1.

3.1 Search strategy

This study conducted a systematic search of the following databases for relevant literature: Web of Science, Scopus, ProQuest (Social Science, Political Science, Aerospace Technology, Advanced Technologies, and Computer Science), and Policy Commons. Web of Science and Scopus offered broad multidisciplinary coverage suited to the socio-technological nature of the research focus, while ProQuest databases provided targeted coverage across social sciences and advanced technologies. Policy Commons was included for its emphasis on real-world policy implications.

The search syntax was formulated and expanded around the critical concepts in the central research question—"digital," "sovereignty," "identity," and "national.” By probing academic database topics, the syntax was iterated by testing the relevance of preliminary results. Full search terms are detailed in Appendix 1.

3.2 Inclusion and exclusion criteria

The following inclusion criteria have been applied:

• Peer-reviewed academic literature, including journal articles, literature reviews, and book chapters, as well as high-quality grey literature such as position papers and conference proceedings where peer review status could be verified.
• Literature published between 2015 and 2025, to capture contemporary developments in digital sovereignty and national digital identity systems.
• Literature that discusses both digital sovereignty and digital identity in the context of public digital services
• Studies that address one or more of the following research themes:
  • technology and infrastructure,
  • governance processes, and
  • implementation and adoption.
• Literature published in English

The following exclusion criteria have been applied:

• Academic literature that has not been peer-reviewed
• Any literature not authored, or available in, English
• Literature that is not available online through University College London (UCL) institutional access
• Literature that discusses sovereignty, self-determination, or identity in a non-digital context (e.g., ethnic or national identity debates without a technological dimension).
• Literature that primarily focuses on commercial or private-sector digital identity systems without relevance to public service provision or national governance.

3.3 Screening process

Studies were manually screened at title/abstract and then at full-text. Initial screening retained studies that discussed both digital sovereignty and national digital identity systems. Full-text screening prioritised records engaging one or more research sub-themes.