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@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@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@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@bio.gla.ac.uk] Sent: Tuesday, June 05, 2007 2:10 PM To: Chuck Miller Cc: Bob Morris; Kevin Richards; tdwg-guid@lists.tdwg.org; WEITZMAN@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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