abstract:A persistent identifier (PI) is a long-lasting reference to a digital object—a single file or set of files. Noted persistent identifier systems include: Archival Resource Keys (ARKs), Digital Object Identifiers (DOIs), Persistent Uniform Resource Locators (PURLs), Uniform Resource Names (URNs), and Extensible Resource Identifiers (XRIs).
However, no parental notice and consent is required when an operator collects a persistentidentifier for the sole purpose of supporting the website or online service's internal operations, such as contextual advertising, frequency capping, legal compliance, site analysis, and network communications.