[tdwg-guid] Globally unique vs. globally locatable
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Hi folks,
Here is another issue from that discussion thread that I'm splitting: (simply) globally unique vs. globally locatable. As Chuck said:
1. An identifier that is simply globally unique - that is, the id is never duplicated and always refers to the same thing. So, you can use it as a unique reference in a paper, like an ISBN/ISSN number. But more importantly, it also can be used in data files/serialized XML to enable computers to quickly compare import/export records for merge/update, which is an important function to many, many biodiversity data projects. But, this id does not itself tell you where it can be found. Its location must come from another source.
2. An identifier that is globally locatable via the Internet - that is, the id is never duplicated and always locates the same thing (with a further definition needed of what the thing is). The globally locatable identifier needs to be locatable by a web browser (HTTP) but more importantly also by web services which may want to use a different protocol.
I would argue that, without loss of generality, any identifying scheme considered by this group (LSID, DOI, Handles, ARK and any HTTP URL based scheme) fulfill both use cases. Since we are interested in sharing data, the 2nd use case is far more important for us than the first. For that reason, I would suggest that any other scheme that provide globally unique but non-locatable identifiers (i.e. that fulfill use case #1 but not #2) would be irrelevant to this group.
Such a scheme would still be important for cases other than sharing data, but that discussion would be outside of the scope of this group.
If you are interested in discussing the best way to make your local identifiers globally unique (which was the issue that started this discussion I suppose), that's the subject of another (very relevant) thread. For now the only thing I'll say about that is that there are guidelines for making local identifiers globally unique in each identifying scheme. In the particular case of LSIDs you may find information about that in the following documents:
* The LSID Specification - http://www.omg.org/cgi-bin/doc?dtc/04-05-01) * LSID Best Practices (Naming conventions) - http://www-128.ibm.com/developerworks/opensource/library/os-lsidbp/ * LSID Namespaces discussion - http://wiki.tdwg.org/twiki/bin/view/GUID/LSIDResolverNamespaces
In any case, rest assured that we will sum up all those guidelines into a section of the Bratislava Declaration ;)
Cheers,
Ricardo
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On 13 Jun 2007, at 17:52, Ricardo Pereira wrote:
I would argue that, without loss of generality, any identifying scheme considered by this group (LSID, DOI, Handles, ARK and any HTTP URL based scheme) fulfill both use cases. Since we are interested in sharing data, the 2nd use case is far more important for us than the first. For that reason, I would suggest that any other scheme that provide globally unique but non-locatable identifiers (i.e. that fulfill use case #1 but not #2) would be irrelevant to this group.
Just to be contrary, I think case #1 will still be highly relevant, especially for the task of figuring out whether two GUIDs issued by different sources refer to the same thing. For example, many taxonomic database are likely to share the same publications, and if they issue their own identifiers for those then there will be multiple GUIDs for the same publication.
Some poor fool will have to reconcile these at some point. This is what I spend most of my time doing, and it is not fun. To give a concrete example, if the metadata for a journal article includes the ISSN of the journal and/or a SICI for the article, then inferring that the two articles are the same is much easier. ISSNs and SICIs are both globally unique identifiers that are not, by themselves, resolvable.
In a sense this is an argument for separating identifiers from resolution mechanism, and for having a canonical representation of identifiers. For example, if I want to refer to a DOI in metadata for a publication, do I refer to this as:
http://dx.doi.org/10.1643/CH-04-083R1, or doi:10.1643/CH-04-083R1, or 10.1643/CH-04-083R1, or info:doi/10.1643/CH-04-083R1 ?
The INFO URI scheme addresses some of these issues. The first (http://dx.doi.org/10.1643/CH-04-083R1) seems problematic because if doi.org restructures their website this proxy may disappear (unlikely given the howls of protest that would ensure, but not impossible).
I guess my concern in all of this is that there are some items for which only a single GUID is likely to ever be issued (specimens in a museum or institution database), and items where multiple GUIDs are likely (literature, names, concepts). It's the shared stuff that will make biodiversity informatics fly, so having mechanisms to avoid massive duplication of these would be desirable.
Regards
Rod
Such a scheme would still be important for cases other than sharing data, but that discussion would be outside of the scope of this group.
If you are interested in discussing the best way to make your local identifiers globally unique (which was the issue that started this discussion I suppose), that's the subject of another (very relevant) thread. For now the only thing I'll say about that is that there are guidelines for making local identifiers globally unique in each identifying scheme. In the particular case of LSIDs you may find information about that in the following documents:
- The LSID Specification - http://www.omg.org/cgi-bin/doc?dtc/04-05-01)
- LSID Best Practices (Naming conventions) -
http://www-128.ibm.com/developerworks/opensource/library/os-lsidbp/
- LSID Namespaces discussion -
http://wiki.tdwg.org/twiki/bin/view/GUID/LSIDResolverNamespaces
In any case, rest assured that we will sum up all those guidelines into a section of the Bratislava Declaration ;)
Cheers,
Ricardo _______________________________________________ tdwg-guid mailing list tdwg-guid@lists.tdwg.org http://lists.tdwg.org/mailman/listinfo/tdwg-guid
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participants (2)
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Ricardo Pereira
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Roderic Page