I think this is a very nice statement of the issues.

My own view is that ARK is interesting, but I'm not sure ARK is the best way forward. Persistence is a (perhaps the) key issue, and it is a social one not a technological one, as the DOI people make very clear. DOIs only work because the publishing industry has invested in the infrastructure to support them.

In some ways, DOIs and ARK are very similar. If I use the DOI resolver to resolve a DOI

http://dx.doi.org/10.1086/303303 --------/ -----/ ----/ | | | | Name Name Name mapping Assigning Authority Authority Number (NAAN) Hostport (NMAH)

then I have a URL very like an ARK, where the authority assigning the name (such as a publisher, in this case the University of Chicago) is different from the authority makes the identifier actionable (doi.org). One could imagine that if DOI.org were to fall over, one could substitute another authority, such as doi.reborn.org. Indeed some publishers almost do essentially this, for example http://www.journals.uchicago.edu/cgi-bin/resolve?id=doi:10.1086/303303 (although this will only resolve local DOIs). ARK simply makes this possibility explicit. LSIDs are more strongly tied to the DNS (the uniqueness of an LSID is partly guaranteed by using Internet domain names), although they do have limited support for foreign authorities (other providers that can serve metadata for objects that those providers don't actually own).

ARK also adds the ability to retrieve a statement of commitment. I'm less impressed by this, as a statement is all very well, but will service providers actually honour it? I guess this is an issue of trust. I suspect that user's rating of service providers will be much more accurate than a rating provided by a service provider.

One issue not on this list is who generates GUIDs? ARKs and DOIs require some degree of centralisation because both require unique identifiers for organisations providing data (e.g., 10.10086 identifies the University of Chicago Press). This in itself requires some degree of service commitment. LSIDs are decentralised, in that the unique identifier for an organisation is provided by the DNS. If, for example, GBIF took on the role of providing unique identifiers for organisations, but then closed due to funding issues (heaven forbid), then we have a problem. If the DNS goes belly up, then we will have much more pressing issues to worry about...

Regards

Rod

On 11 Oct 2005, at 15:37, Donald Hobern wrote:

[ I will be trying to provide some structure to discussions in this mailing list by raising specific topics and looking for comments.  Please keep the Topic number in responses ]   Topic 1: What do we mean by GUID?   The most fundamental thing that we need to establish as we consider a GUID implementation is a definition for “GUID” in this context.  We have been using a number of terms to describe the identifiers we need (unique, resolvable, persistent, etc.).     I’ve been spending some time following up on Rod Page’s recommendation that we consider the use of Archival Resource Keys (ARK) from the California Digital Library (see http://wiki.gbif.org/guidwiki/wikka.php?wakka=ARK).  The CDL web site includes an excellent overview of this GUID model, which also serves as an excellent introduction to the issues involved.  I would urge you all to read this document – it’s only nine pages long!):   http://www.cdlib.org/inside/diglib/ark/arkcdl.pdf   This document arrives at the following problem definition for persistent, actionable identifiers:   1 The goal: long-term actionable identifiers. a Requirement: that identifiers deliver you to objects (where feasible). b Requirement: that identifiers deliver you to object metadata. c Desirable: each object should wear its own identifier. d Requirement: that identifiers deliver you to statements of commitment. 2 The problem: URLs break for some objects (that is, associations between URLs and objects are not maintained), and we have no way to tell which ones will or won’t break. 3 Why URLs break: because objects are moved, removed, and replaced – completely normal activities – and the provider in each case demonstrates insufficient commitment to update indirection tables, or to plan identifier assignment carefully. Persistence is in the mission of few organizations. 4 Conventional hypothesis: use indirect names (PURLs, URNs, Handles) instead of URLs; what worked for DNS should work for digital object references.  Wrong. Indirection is spectacularly successful and elegant in DNS, but it’s a side issue in the provision of digital object persistence.   This document clearly identifies issues around provider service commitments as the key problem that needs solving.  The construction of ARKs seeks to address this in a couple of ways.  It separates the role of Name Assigning Authority (i.e. who initially assigns the identifier) from that of the Name Mapping Authority (i.e. who is able to map the identifier to the data object at any particular time).  It also defines a simple standard relationship between three things: the data object, the metadata for the object, and a commitment statement from the provider as to what aspects of persistence are guaranteed.   ARK is a technology that we have not really considered up to this point.  My question for discussion is what, if anything, is missing or wrong about the problem definition provided in this document?  If we agree that it provides a crisp definition of what we need, that in itself will be a major step forward.   Please provide your thoughts.   Donald

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Donald Hobern (dhobern@gbif.org) Programme Officer for Data Access and Database Interoperability Global Biodiversity Information Facility Secretariat Universitetsparken 15, DK-2100 Copenhagen, Denmark Tel: +45-35321483   Mobile: +45-28751483   Fax: +45-35321480

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Professor Roderic D. M. Page Editor, Systematic Biology DEEB, IBLS Graham Kerr Building University of Glasgow Glasgow G12 8QP United Kingdom

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