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Royal Danish Library uses PWID as the recommended way to reference web archive material

The Persistent Web IDentifier (PWID) is used for creation and resolving of precise and persistent references to data in web archives. PWID was created as there was no proper way of referring precisely and persistently to data in one or more web archives. A PWID can be specified in two ways as a Uniform Resource Name (URN) as a textual reference, e.g. by using the ISO-690 standard

The image is from digitalbevaring.dk

PWID is constructed in a way that makes it both human readable and algorithmically resolvable by tools in form of a URN. PWID is useful in research data management based on material from web archives, but also as reference to web material in research reports and papers. The creation of PWID is a result of a research project in 2016, with participants across research fields, which made it possible to bridge the gap between humanities and computer science research.

Further work will be to establish some kind of registry for web archives for identification (e.g. via domains) of web archives as part of PWID (e.g. via International Internet Preservation Consortium/IIPC). Another initiative is creation of a PWID-URN resolver, which currently exists only as a prototype (and might end up as e.g. a Open Preservation Foundation/OPF tool).

PWID is presented in various litterature, posters and presentations. You will find most of it in the following lists of updated PWID descriptions, examples of use, and historical background.

Formal PWID URN description

• Zierau, E.: “URN Namespace Registration for Persistent Web IDentifiers (PWID)”, 2022.
  urn:pwid:archive.org:2022-11-27T18:33:21Z:part:https://www.iana.org/assignments/urn-formal/pwid,
  Live version: https://www.iana.org/assignments/urn-formal/pwid

Other PWID descriptions

• Nyvang, C., Zierau, E.: "The Potentials and Challenges for Researchers and Web Archives Using the Persistent Web IDentifier (PWID)", at Web Archiving Conference 2024 – IIPC-WAC, Paris. 2024.
  urn:pwid:archive.org:2024-08-12T12:02:54Z:page:https://netpreserve.org/ga2024/programme/wac/
  Video of presentation: youtube-video
• Updated version of Poster at the 15th International Conference on Digital Preservation (iPRES),
  urn:pwid:archive.org:2022-12-12T17:14:47Z:part:http://id.kb.dk/pwid/PWID.ppsx
  Live version: http://id.kb.dk/pwid/PWID.ppsx

Recommondations of/tools for PWID

The following includes services to construct and resolve a PWID for a selection of web archives. There are plans to make similar more general tools.

• Österreichische Nationalbibliothek: "Wie zitiert man Webinhalte richtig?"
  urn:pwid:archive.org:2025-04-07T20:35:49Z:page:https://www.onb.ac.at/mehr/blogs/detail/wie-zitiert-man-webinhalte-richtig
  Live version: Wie zitiert man Webinhalte richtig?

Use of PWID

The following includes both descriptions of use of PWID - and provides examples on use of PWID as part of references in papers, journals and books.

• Zierau, E., Cannelli, B., Chambers, S., Holownia, O., Healy S., Laursen, D., Aasman, S, Have, U. K.: "Towards transnational research data management practices for web archives: challenges and possibilities", In book "Companion to Transnational Web Archive Studies", Brügger, N., Aasman, S., Ben-David, A. (ed.), published April 2025.
• Zierau, E., Møldrup-Dalum, P.: "Making web collections for research Sustainable and Reusable, Possibilities and Challenges experienced", at Web Archiving Conference 2021 – IIPC-WAC, Luxenborg. 2021
• Mette Kia Krabbe Meyer, Zierau, E.: "Spitting Image - Press photographs and memes as digital cultural heritage in Netarkivet", in Fund og Forskning, Det Kgl. Bibliotek, Copenhagen, Vol 58. 2019.
• Mette Kia Krabbe Meyer, Zierau, E.: "Remaking the 'spitting man', The creation, recreation and archiving of a photomeme", at Digital Humanities in the Nordic Countries: 4th Conference. 2019.
• Nyvang, C., Kromann, T., Zierau, E.: "Det levende web og de døde links", In Nordisk Tidsskrift for Informationsvidenskab og Kulturformidling, vol. 6 no. 1. 2017.
• Jurik, B., Zierau, E.: "Data management of web archive research data", In proceedings of Researchers, practitioners and their use of the archived web conference (IIPC/RESAW 2), London, DOI:10.14296/resaw.0002. 2017.

Web archive registry work

• Zierau, E.: "Next Steps Towards A Formal Registry Of Web Archives For Persistent And Sustainable Identification", Poster from Web Archiving Conference 2025 – IIPC-WAC, Oslo. 2025
• Zierau, E., Tønnessen, Myrvoll, A.: "Towards A Formal Registry Of Web Archives For Persistent And Sustainable Identification", at Web Archiving Conference 2024 – IIPC-WAC, Paris. 2024. urn:pwid:archive.org:2024-08-12T12:02:54Z:page:https://netpreserve.org/ga2024/programme/wac/
  Video of presentation: youtube-video

Historical background

• Zierau, E.: "Precise and Persistent Web Archive References - Status and expected progress of the PWID", Poster at the 15th International Conference on Digital Preservation (iPRES), DOI:10.17605/OSF.IO/U5W3Q. 2018.
• Nyvang, C., Kromann, T., Zierau, E.: "Capturing the web at large: a critique of current web referencing practices", in proceedings of Researchers, practitioners and their use of the archived web conference (IIPC/RESAW 2), London, DOI:10.14296/resaw.0004. 2017.
• Zierau, E., Nyvang, C., Kromann, T.: "Persistent Web References – Best Practices and New Suggestions", in proceedings of the 13th International Conference on Digital Preservation (iPRES). 2016.