What is a "DOI"?

Short Answer

A digital object identifier (DOI) is a persistent identifier or handle used to identify objects uniquely, standardized by ISO, the International Organization for Standardization (see https://en.wikipedia.org/wiki/Digital_object_identifier).

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The allocation of DOIs for research data sets ensure that the data are permanently linked and accessible via the resepective respective DOIs. This means that they can be referenced at any time, even if the web address from which the data can be downloaded changes over time. In GFBio, the assignment of DOIs is a free service of the participating data centers, which is integrated into the data submission process.