Frequently Asked Questions (FAQ)

The FAQ page will be successively extended by further questions within the project duration. Detailed information can be found on the page of the PID Competence Center of our project partner TIB.

PID is the abbreviation for Persistent Identifier. They are "unique, universal, and persistent identifiers" (Koster, 2020):

  • "identifier"= a string of characters that refers to an object
  • "unique"= refers to only one object (within the known universe)
  • "universal"= applies to the whole world (or the World Wide Web)
  • "persistent"= remains available regardless of individual institutions, systems, or system implementations

They refer to digital or physical objects or abstract concepts. They are usually "actionable," meaning they can be represented as a URL that leads to the identified source or to a landing page with metadata information.


PIDs are usually organized in institutionally managed systems. Persistence is primarily a question of service! Agents are always needed who operate the PID service in a technically and organizationally reliable manner. Open infrastructures, associated metadata and services, such as APIs, enable the resolution of PIDs.

A PID string is structured according to a uniform scheme.

Example: DOI have the format prefix/suffix.

A DOI formatted as a URL:


  • PIDs prevent broken links (i.e. a URL is no longer resolved because the resource has been relocated or is permanently unavailable).
  • They enable unique identification of publications, records, individuals, organizations, research materials, and much more....
  • Especially in academia, they provide useful standards for unique citations.
  • PIDs can be used to provide unique links to other PIDs, such as linking professional articles or researchers and their datasets.
  • PIDs facilitate the comprehensive and accurate attribution of research articles (publications, datasets, conference papers, etc.) to scientific records.
  • The use of PIDs is recommended by important research funding bodies and organizations, e.g. in the code "Guidelines for Ensuring Good Scientific Practice" of the German Research Foundation or in Plan S of the "Coalition S".