PubDIDs (and DIDs in general, maybe)

[Norman Gray]

Alberto and all, hello.

On 2014 Jan 16, at 15:14, Accomazzi, Alberto <aaccomazzi at cfa.harvard.edu> wrote:

+1 generally, but...

> I think a better way to keep this straight is to think of the "ADS" identifiers as URNs and the ivo identifiers as URIs.

Unleashing my inner lawyer: recall that URNs are (according to RFC 2396) merely one of the two types of URIs, namely "the subset of URI that are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable."

RFC 3968 <https://www.ietf.org/rfc/rfc3986.txt> mentions that '[a] URI can be further classified as a locator, a name, or both', and that '[t]he term "Uniform Resource Name" (URN) has been used historically to refer to both URIs under the "urn" scheme', but that 'Future specifications and related documentation should use the general term "URI" rather than the more restrictive terms "URL" and "URN".'

All that said...

> 6. Having said all of this, I still do have one basic question about the ivo identifiers that you want to use in datalink, based on my current understanding of them.  Specifically, given that these lack persistence and multiple resolution features, why bother at all rather than using a plain http uris?  I think this question is worth considering now since the experience with the dataset ids has taught me that unless there are compelling reason to go with a discipline-specific, custom solution you may be better off using what the web already gives you for free: namely http and dns.

I think this is a really important point, which isn't made often enough (cue hobbyhorse).  Without _necessarily_ discounting the existence of such 'compelling reasons', non-standard schemes do come with a cost, and they're not magic, so that if your resolution mechanism disappears, a URN-named object is just as lost, and just as nameless, as one named with a 404ed HTTP URI.

I remember a workshop on persistent identifiers of a few years ago, where Stuart Weibel (I think; or it may have been John Kunze) made this point very convincingly.  Something under purl.org or under id.loc.gov has an "institutional commitment to persistence" which is worth an awful lot more than any amount of indirection that you get through a fancy URI scheme.  As Stuart (or whoever) said , "loc.gov isn't going away any time soon".

DOIs do, I think, have a pretty compelling reason to be a special URI scheme, but the thing that's key about DOIs is not the scheme, or the Handle-based lookup mechanism, but precisely the "institutional commitment to persistence" that they represent.

I don't plan to reopen any discussion here about IVORNs -- fear not, everyone -- but will simply note that, on general principles, obsessing about the punctuation of URIs is probably a distant second in importance to developing and planning these sorts of institutional commitments within the IVOA.

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK