What is a DOI?

A DOI (Digital Object Identifier) is a unique alphanumeric identifier applied to a specific piece of intellectual property, particularly one presented in an online environment -- be that object a book, a scientific paper, a song, an image, or something else. Unlike a conventional Web address, or URL, a DOI specifies not the location of an online object, but rather its content; a DOI is thus a "persistent" identifier, and remains associated with the object irrespective of changes in the object's Web address.

All Science articles currently are assigned a DOI, which can be found at the top of the article's HTML version. DOIs also form a key component of certain reference-linking systems such as CrossRef. For more information, visit the Web site of the International DOI Foundation.