The Handle System of Persistent Identifiers

The Handle system is a popular choice for the assignment and resolution of globally unique, persistent identifiers. Governance is centralized with the DONA Foundation, and administration is distributed among so-called Credentialed Multi-Primary Administrators (MPAs), of which there are currently nine. You’ve likely heard of at least one MPA: the International DOI Foundation.

Each MPA is assigned a number. The DOI Foundation has 10. This is why all DOIs begin with 10.. Each MPA can in turn give a “complete” prefix (everything before the /) to a so-called “naming authority”. The DOI Foundation1 gave the Nature Publishing Group (now Springer Nature) 10.1038, for example, who in turn can create as many local names as they’d like, such as 10.1038/sdata.2016.18.

How do handles get resolved? Each handle prefix may have its own administrator, and administration of handles is distributed, similar to the Domain Name System (DNS). The Handle system is compatible with DNS, but does not require it. In practice, there are known public HTTP proxy servers such as https://hdl.handle.net/ and https://doi.org/ that allow resolution of handles as URLs. Hence, https://doi.org/10.1038/sdata.2016.18 is resolvable.

Another big MPA is the Corporation for National Research Initiatives (CNRI). CNRI governed the Handle system before passing it off to the formed-for-this-purpose DONA Foundation in 2015. Before this, CNRI assigned MPA-esque numbers to a bunch of organizations, and these continue to be administered by the CNRI-as-MPA, even though it’s assigned number is 20 now. For example, CNRI assigned 1721.1 to MIT, which is used for it’s DSpace repository. My PhD thesis was assigned 1721.1/71495. So, https://hdl.handle.net/1721.1/71495 and https://doi.org/1721.1/714952 (and https://dspace.mit.edu/handle/1721.1/71495) all get you to it.

You can inspect Handle prefix records, which are analogous to DNS records, via https://hdl.handle.net/. For example, https://hdl.handle.net/1721.1 lets you know that this prefix is administered by MIT DSpace via the CNRI MPA (see the /20.ADMIN-containing HS_ADMIN entry).

So how do you start minting and resolving Handles?

Become a credentialed MPA? I don’t know, that seems hard for an individual researcher. There are only nine credentialed by DONA.

Request a completed prefix from an existing MPA, e.g. something that matches 10.\d+ from the DOI foundation? Yes, you can do that. MPAs typically charge registration and annual service fees per allotted prefix (i.e., the whole .-delimited number before the / in a handle). In the case of the DOI Foundation, they delegate to e.g. Crossref to assign 10. prefixes. In this case, for additional fees, Crossref will resolve identifiers for you (beyond assigning you a prefix to mint as many as you’d like).

A final method is to find a service provider that has a complete prefix and will let you mint handles under their prefix, or will mint them for you. This is the most typical route for researchers. For example, Zenodo got 10.5281 from DataCite (another 10.\d+ service provider the DOI Foundation delegates to), and they’ll give you a full handle when you upload stuff to https://zenodo.org. ResearchEquals got 10.53962 from CrossRef, and they’ll give you one for anything you put on https://www.researchequals.com/. And of course, journal publishers typically give you one when you publish an article with them.

1. Actually, one of its registration agencies (RAs), Crossref. The DOI Foundation doesn’t give out prefixes directly. Individuals request prefixes from RAs, not from the DOI Foundation. Thank you Ed Pentz for clarifying this. [footnote added 2022-07-01] ↩︎

2. Wait, what? It’s a DOI? Nope. DOIs are Handles that start with 10.. https://doi.org/ is (currently) a public HTTP proxy server that resolves all Handles, regardless of prefix. ↩︎