A persistent identifier (PI or PID) is a long-lasting identifier to a document, file, web page, or other object.The term "persistent identifier" is usually used in the context of digital objects that are accessible over the Internet. Typically, such an identifier is not only persistent but actionable: you can plug it into a web browser and be taken to the identified source.

Of course, the issue of persistent identification predates the Internet. Over centuries, writers and scholars