Old:Identifiers

STATUS: This page is outdated and of historical use only.

'''Dryad has decided to use DOIs for all objects in the repository. For details, see DOI Usage.'''

Handle
Pro:
 * Handles are native to DSpace.
 * Handles have the same basic architecture as DOIs, but are much less expensive to implement. The total cost is about $100 per year, regardless of the number of identifiers.

Con:
 * Must register the local resolver with a central service.

DOI (Digital Object Identifier)
DOIs are one particular implementation of handles, used widely in the publishing industry. One difference is that the DOI system mandates metadata that must be associated with every DOI, while "plain" handles (and most other ID systems) leave metadata up to the user.

Pro:
 * Publishers and scientists are already familiar with them
 * Supported by ISI (though they may not consciously be supporting DOIs for data objects)
 * CrossRef provides searching and citation linking services for DOIs in the CrossRef system (it is unclear whether a DOI issued by another agency can be listed in the CrossRef system).

Con:
 * Must register the local resolver with a central service.
 * Must pay to register each identifier. TIB charges 60 cents per identifier, though this cost will come down through the DataCite collaboration. CrossRef charges 6 cents per data file identifier and $1 for each database identifier (though it is unclear what constitutes a database). These costs are trivial for a one-identifier-per-article model, but can be quite expensive for more granular schemes, such as the one-identifier-per-observation model that would be ideal for fully machine-readable data.

DOI + Handle (hybrid)
An old post from Rod Page suggests using DOIs for manuscript-level information and handles for more granular information. This would hold down costs, but could be messy.

Pro:
 * Allows DOIs to be used at the level of a whole article (data package), which is the level where DOI provides the most benefits.
 * Since the DOI and handle technologies are nearly identical, only a single service needs to be maintained for resolving identifiers.

Con:
 * May be confusing for authors, especially if a single publication cites datas at both the DOI and handle levels.

DOI parameters
Generic DOIs may be registered, and parameters may be added to access sub-parts of the DOI object.

Pro:
 * This allows us to limit the number of DOIs registered, while providing access at any granularity we wish.

Con:
 * The resultant URLs are long and complex
 * The parameter passing mechanism may change over time, making this approach poorly suited for persistent identifiers.

LSID (Life Science Identifier)
LSID is a URN identifier scheme.


 * TDWG working groups
 * GBIF has some association with LSIDs, but not as a primary identifier for the GBIF repository.
 * BioMoby uses LSIDs for internal processing.
 * LSID vocabulries

Pro:
 * (there are no obvious pros of LSIDs, when compared to DOIs and Handles)

Con:
 * There are no known sites that use LSIDs as their primary identifier, though a few sites (available from the LSID homepage) can resolve LSIDs into their identifier scheme.
 * LSIDs seem to have fallen out of favor as people have realized that URLs can be identifiers, and tools for other identifier schemes have improved.
 * Unclear whether a central resolution authority really exists
 * Community is much smaller than for other identifier schemes
 * The W3C has written a document that claims non-http schemes aren't any better than http-based schemes.

UNF
UNF is a content-based identifier for data objects, somewhat like a fingerprint.


 * description at the Dataverse Network

Pro:
 * The UNF can help to detect errors in transcribing identifiers.

Con:
 * The UNF is not easy for humans to interpret.
 * The UNF code only works with file formats used by statistical software.

Identifier schemes in use
Almost all repositories of publications use DOI, but data repositories vary more:
 * CiteSeer: custom
 * ChemXSeer: doi, custom
 * GenBank: accession
 * PubMed: custom
 * GBIF: custom
 * KNB: custom
 * OceanPortal: accession
 * Morphbank: accession
 * MorphoBank: accession
 * National Climatic Data Center: custom
 * Paleobiology Database: accession
 * TreeBASE: custom
 * World Data Center: doi
 * PDB: custom, doi
 * Pangaea: doi

Notes/Decisions

 * We do not want to fall into the same trap as arXiv. They were forced to change their identifier system, because the number of items added to the repository could no longer be accommodated by old scheme. However, the new scheme is still inflexible, and is guaranteed to be invalid eventually, because they include a 2-character year code.
 * Mike Giarlo says the choice of identifier scheme doesn't really matter, the commitment to persistence is key.
 * Ryan's previous thoughts on semantic vs. non-semantic identifiers.
 * CrossRef suggests creating DOIs of the form DOI-institution-code/Handle-institution-code/Handle-specific-part. These will trivially convert to a form that DSpace can use.