The DOI, or digital object identifier, serves as a persistent, actionable identifier for intellectual property online. DOIs can be assigned at any level of granularity, and therefore provide publishers with an extensible platform for a variety of applications. And DOI links don't break. Even if a publisher needs to migrate publications from one system to another, or if the content moves from one publisher to another, the DOI never changes. This means that all the links to that content that have already been made still function. Hence, one key insight of the DOI model is persistence; the other is actionability. One click on a properly implemented DOI gets the reader to the location of the material they want.
-As copied from the CrossRef.org web site.
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