The requirements of FAIR and Reproducible Science are driving new PID requirements around the citation of exact, verifiable versions of research outputs. For example, versioned DOIs have been implemented on various popular platforms (Figshare, Zenodo, F1000). There is also renewed interest in the idea of data packaging as a practical means of bundling data and metadata in a way that can be easily cited and transmitted as a single payload. Similarly, several groups have identified the need to directly and unambiguously reference the exact content of a data payload in PID metadata: — for example, the Freya project is looking at how best to allow “direct access to content associated with a DOI” (see https://github.com/datacite/freya/issues/2), — RDA is tackling similar issues in the PID Kernel Information Working Group (https://www.rd-alliance.org/groups/pid-kernel-information-wg), — and the Software Heritage made ‘verifiability’ a key property of their PID design (https://hal.archives-ouvertes.fr/hal-01865790). This all suggests an appetite within the research community for greater consensus around linking PIDs to versioned (and therefore immutable), self-describing content. Beyond the scholarly communication ecosystem, a number of projects, notably the Interplanetary FileSystem (IPFS) and DAT, use content-addressed, peer-to-peer networks to bake these properties right into the fabric of the network, in a way that has potentially interesting implications for how we share reproducible research outputs. This talk will provide an overview of these issues, explore some of the emerging solutions in the area, as well as the challenges inherent in new approaches.

1. What you cite is what you get?
Verifiable addressing of immutable, self-describing
research data
Eoghan Ó Carragáin
Persistent Identifiers in Research
ETH Zurich
2019-09-13

3. Can I Use It? “FAIR Digital Objects”
Turning FAIR into Reality 10.2777/1524

4. image: @OA_RHUL
RO-Crate
BDBags
Can I Use It? Portable, self-describing “Data Packages”

5. “The demand for reproducibility of research results is
growing. [There is need] to reference the exact version
of the data that was used to underpin the research
findings, and/or was used to generate higher level
products. ”
Can I Trust it? Citation and versioning of Research Data

6. “Link rot” and “content drift”
https://doi.org/10.1371/journal.pone.0167475
https://doi.org/10.1371/journal.pone.0115253

7. http://example.com/file.dat
file://tmp/file.dat

8. http://example.com/file.dat
file://tmp/file.dat file://tmp/file.dat

9. Web references are mutable & “content
negotiable” by design
http://example.com/file.dat
file://tmp/file.dat file://tmp/file.dat

10. http://example.com/file.dat
http://repo.org/file.dat
http://archive.net/file.dat
DOI redirection/multi-resolution
http://doi.org/10.1234/abcde

11. Can I find it? Persistent Identifiers and link rot

12. Arnap & Hutchinson 2006 10.1145/1179509.1179514
Can I trust it? Persistent Identifiers and content drift
doi: 10.1000/182
2004 (Version 4) 2019 (Version > 6)

13. “persistence is purely a matter of service and is neither
inherent in an object nor conferred on it by a particular
naming syntax. The best that an identifier can do is to
lead users to the services that support robust reference.”
- J. Kunze et al. “The ARK Identifier Scheme”
https://tools.ietf.org/html/draft-kunze-ark-18

14. “The demand for reproducibility of research results is
growing. [There is need] to reference the exact version
of the data that was used to underpin the research
findings, and/or was used to generate higher level
products. ”
Can I Trust it? Citation and versioning of Research Data

15. Can I trust it? DOI Versioning
Any C.U.D. operation on files triggers a new
version.

16. Can I trust it? Allowing content verification with checksums

17. https://hal.archives-ouvertes.fr/hal-01865790
Can I trust it? Content-Addressing for research data?
Content-addressed PID scheme:
swh:1:cnt:94a9ed024d3859793618152ea559a168bbcbb5e2
“Identifiers for Digital Objects” rather than “Digital Identifiers of Objects”

18. “it is really about the ability to trust your data. I guarantee you, if you put your data in Git, you can
trust the fact that five years later after it was converted from your hard disk to your DVD to whatever
new technology and you copied it along, you can verify that the data you get back out is the exact
same as the data you put in.”
- Linus Torvalds
“if you cannot guarantee that what I put in […] comes out exactly the same, your system is not worth using”
Can I trust it? Content-addressed and distributed systems

19. http://site.com/data/pids.pdf
ipfs://zdj7WjqNrjReTcEveRh/pids.pdf
Image: @protocollabs
LOCATION-ADDRESSING
CONTENT-ADDRESSING

20. slide:@flyingzumwalt
http://example.com/file.dat
http://repo.org/file.dat
http://archive.org/file.dat
Replicas compete to be THE LOCATION

21. image:@flyingzumwalt
ipfs://zdj7WjqNrjReTcEveRh
gcsXsJvSGwLxJ7js1R7ZCz
NaQSKuTh

22. Immutability != permanent/persistent availability
● Who coordinates ‘nodes of last resort’ (c.f. LOCKSS, Keepers Registry)?
● Persistent availability of large amounts of research data = Collective
Action Problem (see: 10.5334/kula.7)
How long is long enough?
● Inevitability of hash collisions (at some stage)?
● For the scholarly record, you still need an indirection layer, to be able to
update citations to point at new hashes (sound familiar?)
● Indeed, we need an indirection layer which allows upgrading between
technology stacks and protocols (sound familiar?)
Great, so let’s just use IPFS…?
“persistence is purely a matter of service”

23. title
…
…
contentURL
checksum
“Kernel record/metadata"
Can I trust it? Content-address + Indirection
vDOI

24. Can I trust it? What’s the right recipe?
title
…
…
contentURL
checksum
“Kernel record/metadata"

25. Answers?