In the publishing sector, several standardized codes are used to identify the content that is published, both in print and digital format. These codes or identifiers are characterized by their uniqueness, i.e. they are unique and unrepeatable and identify each product exclusively. They are also persistent, since they identify a product permanently over time.
Some of these identifiers are associated with a specific type of product, such as the ISBN for books or the ISSN for journals, while others provide specific functionalities depending on the format, such as the DOI, the URI or the Handle, which serve both to identify and locate digital products on the Internet. Finally, there are identifiers such as the legal deposit that are associated with the obligation to deposit in a public registry a certain number of printed copies of each publishing product produced in a territory, or a digital archive of the publication, in order to ensure its public access and preservation.