Repeatable:

Yes

It may be possible to have more than one standard identifier, but there should only be one entry per type of standard ID. For example, a published article may have both a DOI and a PubMed ID, but you should only record DOI value and one PubMed ID value.

Recommended Data Entry Type:

Free text or URI

Some standard identifier systems provide values in URI or URL format, meaning the identifier can be written as a functional URL, or using just the ID value. See the Additional detail and Help sections for more information.

Additional detail:

If your encoding standard or authoring tool supports it, it is recommended to specify the type of standard identifier being used, e.g. DOI, Handle, ISSN, ISBN, etc. (Note: the FGDC/CSDGM metadata standard utilizes URLs for identifiers, stored in its Online Linkage element. This element does not, however, provide attributes or properties that allow for differentiating between types or sources of identifiers such as local vs. standard identifier conventions.)

Please also consider the separate Access URL core element, which provides the user with the preferred online access location for the item. It is recommended to limit the overall number of URLs provided in a record in order to emphasize the best way to access the resource. If you have already supplied a URL in the Access URL element, it is recommended to format additional standard identifiers using a non-URL formatted version, if available. See the Help section for more information.

System Tips:

Dataverse generates and stores a Handle ID for each data set uploaded to the repository.

The OpenEmory repository ingests content from external sources. It detects and stores multiple standard identifiers such as DOI, ISSN, PubMed ID, and NIH manuscript IDs.

My item has multiple identifiers - which one should I use?

Recording multiple identifers for the same item is generally beneficial for metadata management, but can provide challenges if systems and users are later unable to differentiate between the types of identifiers. When mapping metadata for use across multiple systems, consider which identifier(s) are the most appropriate for the context in which they will be viewed.

FAQs:

What is a URI? What's the difference between a URI, URL, and URN?

Links and Resources: 

DOI

Handle

ISSN

ISBN