[tdwg-guid] First step in implementing LSIDs
Dave Vieglais
vieglais at ku.edu
Wed Jun 6 23:50:18 CEST 2007
Hi Bob,
it's pretty simple - DNS is used to resolve an ip address to which a
client may connect with a service to resolve the GUID. In the case
of LSIDs the suggested mechanism (and actually the only existing
mechanism) is to use DNS SRV records to provide a level of
indirection that is meant to preserve the discovery of service ip
address independent of the normal issues with A records (although
much of the same functionality can be provided with judicious use of
CNAME and A records). To state that LSID resolution is independent
of DNS is a bit misleading since the entire basis of LSIDs and their
functional utility beyond what can be provided by HTTP uris comes
down to their current use of DNS SRV records for service discovery.
The only negative with LSIDs that I see is the fact that it is a
relatively unknown and so essentially un-implemented protocol. This
makes interoperability with the vast majority of existing
infrastructure more difficult than it needs to be without offering
any advance in functionality. The use of LSID proxy services,
essentially turning LSIDs into URLs is an obvious and welcome
solution, but begs the question of what is really gained by the extra
step of using LSID URIs rather than HTTP URIs?
Perhaps the real benefit is simply that they (LSIDs) look different,
which implies that they need to be handled differently than a typical
URL, and so people and services know immediately to ask a resolver to
return bits (metadata or data) identified by the GUID. The problem
with this of course is that existing services and applications won't
know what to do with them since they are implemented to only
understand http (or perhaps a couple other schemes), and so need to
be re-engineered to handle LSIDs unless the LSIDs are wrapped in HTTP
URLs... One could also argue that it is the context in which an
identifier appears that really indicates what is an identifier rather
than just a string - so in practice the visual appearance of a GUID
shouldn't matter.
Perhaps an adequate solution is to use LSIDs and provide definitive
guidelines indicating how they can be embedded in URLs so that we do
not loose interoperability with the rest of the world? This is
probably much like Ricardo's LSID proxy proposal. Except in my
opinion it should be extended further to be a general GUID resolver
to help resolve whatever form is used for GUIDs - then one could
embed a handle, LSID, HTTP URI, FTP URI, LDAP URI, or even, for the
ancients of the internet, z39.50 URIs in a resolver proxy URL and get
something back. The problem of course is that the content that comes
back will be different for different protocols - but it would, I
suspect be possible to provide a generic form of metadata for the
different protocols.
It would be pretty simple to add some provenance handling to such a
service so that if a particular web server, ftp server, or even LSID
system were moved, then the resolver service could lookup the new
location information and appropriately service the request.
There should of course be multiple instances of such a resolver
service, and the provenance information should be shared and
replicated between them all.
Dave V.
On Jun 6, 2007, at 15:13, Bob Morris wrote:
> I'm confused about what arguments in this thread are about the merits
> of HTTP (e.g. content negotiation) and what are about the merits of
> DNS (e.g. resource and service location). The fact that most humans
> usually exploit these together is because most humans use web browsers
> for discovering resources doesn't have much to do with GUIDs. Even
> LSID resolution itself is actually independent of anything to do with
> DNS, although all current resolvers are based on DNS services.
>
> OK, I confess to not reading all the arguments in detail, but my
> impression is that several of the opposite conclusions from the same
> facts may because one set of conclusions is about service discovery
> and one is about (meta)data provision. It won't surprise me if ANY
> guid scheme is stronger about one of these than the other. This might
> be what Donald is arguing.
>
> Bob
>
> On 6/6/07, Dave Vieglais <vieglais at ku.edu> wrote:
>> This discussion has been very interesting reading, and though I agree
>> with Donald's comments, I find myself coming to a different
>> conclusion, leaning towards HTTP URIs as a preferable scheme. The
>> reasons are simple - HTTP has been around for a long time, it is
>> widely implemented, and mechanisms for implementing robust services
>> with that protocol are pretty well sorted out - and really there is
>> nothing to stop implementation of the same functionality exhibited by
>> LSIDs using HTTP. As Rod has pointed out, http is widely used for
>> referencing entities within a semantic web type of context, and it
>> seems foolish to ignore the momentum in those technologies as they
>> provide a great deal of the desired functionality for
>> interoperability and interchange of our data. As a result my
>> preference is towards the use of http, primarily because my intents
>> are to integrate data from a much broader community. In the end
>> though, it doesn't really matter which scheme is adopted by TDWG - we
>> will build http resolvers regardless, since they will be necessary
>> for reasons of convenience in order to utilize LSIDs in all but
>> specific, custom built applications.
>>
>> However, regardless of the scheme used to implement the GUIDs used by
>> this community, it is critical that the identifiers are persistent
>> and useful beyond the lives of whatever services are constructed to
>> resolve them. This implies some provenance information may need to
>> be captured, and I would argue that the use of DNS alone for handling
>> server changes as utilized by LSIDs may be insufficient. The only
>> benefit provided by DNS in this context is that it is acting as a
>> single source of authority for directing how to locate something (in
>> this case an ip address). What I suspect is really required is a
>> more robust, and richer mechanism for discovering and recording
>> provenance. The ideal would be a large, replicated, and distributed
>> data store with a single service point which provided people and
>> systems with a one-stop shop for discovering provenance for a GUID.
>> Then if an particular GUID could not be directly resolved, the global
>> provenance store could be consulted and the resulting information
>> providing a pointer (or perhaps a series of pointers) indicating how
>> the guid can now be resolved.
>>
>> By creating such provenance records and persisting them with as much
>> care as the data, it seems that a system with stability beyond the
>> vagaries of the internet could reasonably be constructed.
>>
>> regards,
>> Dave V.
>>
>>
>>
>> On Jun 6, 2007, at 00:46, Donald Hobern wrote:
>>
>> > Yesterday was a vacation here in Denmark - otherwise I'd have
>> > responded a little earlier, but I'm glad to see all the comments
>> > from others. I thoroughly agree with Kevin, Jason, Rich and Anna.
>> > No one here believes that any particular solution is going to be
>> > perfect. Our biggest need is consensus and the readiness to get
>> > going with a workable solution.
>> >
>> > I do recognise the strength of Rod's arguments. Indeed, if I were
>> > building some system for integrating data using semantic web
>> > technologies, and my only concern was ensuring the efficiency of
>> > synchronous connections now, I am sure I would adopt HTTP URIs for
>> > the purpose. However I remain convinced (as I've stated before)
>> > that the needs of this community do subtly shift the balance in
>> > another direction. We are interested in maintaining long-term
>> > connections between our objects and have a perspective which goes
>> > back hundreds of years. This at least should give us pause over
>> > whether we want our specimens to be referenced using identifiers so
>> > firmly tied to the Internet of today. More importantly, one of the
>> > key drivers right at the beginning of TDWG's consideration of GUIDs
>> > was that the community had plenty of experience of URL rot and
>> > didn't want to rely on everyone maintaining stable virtual
>> > directories on their web servers to preserve the integrity of
>> > object identifiers.
>> >
>> > Both LSIDs and HTTP URIs could be made to work for us. Both are
>> > totally reliant on good practice on the part of data owners.
>> > Personally I believe our chances of getting the community to
>> > consider, define and apply such practices are enhanced by the
>> > identifier technology being something a little more different and
>> > distinct than just a "special URL".
>> >
>> > Thanks,
>> >
>> > Donald
>> > ------------------------------------------------------------
>> > Donald Hobern (dhobern at gbif.org)
>> > Deputy Director for Informatics
>> > Global Biodiversity Information Facility Secretariat
>> > Universitetsparken 15, DK-2100 Copenhagen, Denmark
>> > Tel: +45-35321483 Mobile: +45-28751483 Fax: +45-35321480
>> > ------------------------------------------------------------
>> >
>> >
>> > On Jun 6, 2007, at 12:51 AM, Kevin Richards wrote:
>> >
>> >> I agree with Jason. It is not the GUID that is the cause of all
>> >> the problems here - THERE IS NOTHING WRONG WITH LSIDS - we just
>> >> need to move on and start using them in our own context (or any
>> >> other suitable GUID - LSIDs are only the recommended GUID, NOT the
>> >> only premissable GUID).
>> >>
>> >> If it all falls to pieces later on we could just do a search and
>> >> replace to change all our GUIDs to some other scheme (to quote
>> >> Bob, just serious).
>> >>
>> >> I agree, it is the RDF/metadata/ontologies that are the key to
>> >> getting things working well.
>> >>
>> >> Kevin
>> >>
>> >>>>> "Jason Best" <jbest at brit.org> 06/06/07 8:39 AM >>>
>> >> Rod,
>> >> I've only had a chance to quickly skim the documents you
>> >> reference, but it seems to me that the alternatives to LSIDs don't
>> >> necessarily make the issues with which we are wrestling go away.
>> >> We still need to decide WHAT a URI references - is it the
>> >> metadata, the physical object etc? URIs don't explicitly require
>> >> persistance, while LSIDs do so I see that as a positive for
>> >> adopting a standard GUID that is explicit in that regard. I think
>> >> the TDWG effort to spec an HTTP proxy for LSIDs makes it clear
>> >> that the technical hurdles of implementing an LSID resolver (SVR
>> >> records, new protocol, client limitations etc) are a bit
>> >> cumbersome, but I don't think the underlying concept is fatally
>> >> flawed. In reading these discussions, I'm starting to believe/
>> >> understand that RDF may hold the key, regardless of the GUID that
>> >> is implemented. Now I have to go read up more on RDF to see if my
>> >> new-found belief has merit! ;)
>> >>
>> >> Jason
>> >>
>> >> ________________________________
>> >>
>> >> From: Roderic Page [mailto:r.page at bio.gla.ac.uk]
>> >> Sent: Tuesday, June 05, 2007 2:10 PM
>> >> To: Chuck Miller
>> >> Cc: Bob Morris; Kevin Richards; tdwg-guid at lists.tdwg.org;
>> >> WEITZMAN at si.edu; Jason Best
>> >> Subject: Re: [tdwg-guid] First step in implementing LSIDs?
>> [Scanned]
>> >>
>> >>
>> >> Maybe it's time to bite the bullet and consider the elephant in
>> >> the room -- LSIDs might not be what we want. Markus Döring sent
>> >> some nice references to the list in April, which I've repeated
>> >> below, there is also http://dx.doi.org/10.1109/MIS.2006.62 .
>> >>
>> >> I think the LSID debate is throwing up issues which have been
>> >> addressed elsewhere (e.g., identifiers for physical things versus
>> >> digital records), and some would argue have been solved to at
>> >> least some people's satisfaction.
>> >>
>> >> LSIDs got us thinking about RDF, which is great. But otherwise I
>> >> think they are making things more complicated than they need to
>> >> be. I think this community is running a grave risk of committing
>> >> to a technology that nobody else takes that seriously (hell, even
>> >> the http://lsid.sourceforge.net/ web site is broken).
>> >>
>> >> The references posted by Markus Döring were:
>> >>
>> >> (1) http://www.dfki.uni-kl.de/dfkidok/publications/TM/07/01/
>> >> tm-07-01.pdf
>> >> "Cool URIs for the Semantic Web" by Leo Sauermann DFKI GmbH,
>> >> Richard Cyganiak Freie Universität Berlin (D2R author), Max Völkel
>> >> FZI Karlsruhe
>> >> The authors of this document come from the semantic web community
>> >> and discuss what kind of URIs should be used for RDF resources.
>> >>
>> >> (2) http://www.w3.org/2001/tag/doc/URNsAndRegistries-50
>> >> This one here is written by the W3C and addresses the questions
>> >> "When should URNs or URIs with novel URI schemes be used to name
>> >> information resources for the Web?" The answers given are "Rarely
>> >> if ever" and "Probably not". Common arguments in favor of such
>> >> novel naming schemas are examined, and their properties compared
>> >> with those of the existing http: URI scheme.
>> >>
>> >>
>> >> Regards
>> >>
>> >> Rod
>> >>
>> >>
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