Terminology of Persistent Identifiers (PIDs)

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An identifier once assigned will never be assigned again to another object. At the level of persistent identifier syntax, this requires management and control also from PID Managers and PID Owners. A prefix (PID syntax component) needs to be also globally unique. 

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Machine Actionable means that a formal statement is syntactically and semantically specified, enabling computing systems to carry out automatic processing.

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Capacity of computational systems to find, access, interoperate, and reuse data (or metadata) with none or minimal human intervention. 

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A human-readable page, displayed in a browser, that provides human users with information on how to access and/or interpret the digital object or its representation that is identified by a PID.

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A set of details associated with a deleted resource. It ensures that information can also be provided after the removal of an entity.

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A namespace ensures that all identifiers within a given level have unique names, allowing them to be easily identified.

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A PID stack is a conceptual framework that includes the components required to ensure persistent identification and access.

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An organisation or decentralised community mechanism responsible for maintaining the rules for defining the integrity of PIDs within a PID Schema. PID Authorities led by organisations typically enforce control over a PID infrastructure (owns the PID schema and directs its management and development), while decentralised solutions provide community standardisation mechanisms that specify how PIDs conform to a PID Schema.

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The set of PID Components and Services that may be federated or interoperable to support EOSC and research that is FAIR in an effective and sustainable way.

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PID Manager is responsible for managing identifiers and their kernel metadata. PID Managers have responsibilities to maintain the integrity of the relationship between entities and their PIDs, in conformance to a PID Scheme defined by a PID Authority. A PID Manager will typically subscribe to PID services to offer functionality to PID Owners within the PID Manager’s services. For example, PID Managers may include a provider of a data repository, a data catalogue, or a research workflow system. ​

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PID Meta Resolver (PIDMR) is a generic resolver that makes it possible to resolve PIDs from a wide variety of systems and providers.

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An actor (an organisation or individual) who has the control to create a PID, assign PID to an entity and provide and maintain accurate Kernel Information for the PID. It must be clear at all times who is the PID Owner, for example through metadata. The PID Owner is responsible for proper management of PIDs and to keep the attribute set up-to-date. 

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Service that enables the creation and administration of PIDs and their relation to the objects they identify. Basic services comprise registration, resolution and curation of PID records. Additional services include support for PID registry searches, extended metadata catalogues and knowledge graph extensions.

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An actor, for example, a researcher, software or service that creates, resolves and uses the information contained in PIDs either directly or indirectly.

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An organisation which provides PID Services in conformance to a PID Schema, subject to the corresponding PID Authority. PID Service Providers are responsible for the provision, integrity, reliability and scalability of PID Services, in particular the issuing and resolution of PIDs, but also lookup and search services, and interoperability with generic resolution systems, e.g. the PID MetaResolver. 

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PID roles, defined in EOSC PID Policy, define roles and responsibilities related to PID use and management.

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A set of rules and standards defining the nature of a Persistent Identifier (e.g. definition of associated metadata, quality assurance conditions, usage rights, terms and conditions, etc). The PID Schema should be machine-actionable.

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The PID Kernel Information Profile describes the set of Kernel attributes that are being selected by a repository to describe the digital object. The profile is dependent on the type of entity and the needs of the community. Only openly declared attributes with widely agreed semantic types will provide machine actionability.

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A PID syntax component denoting an authority or division of a namespace. A prefix needs to be globally unique associated with particular local authorities which are free in how they generate locally unique IDs. 

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The PIDs should be managed and governed in such a way that the community can trust them to remain unique and resolvable for the long term. Also, the syntax of the PID system should  be persistent. Finally, persistence also relates to the object to which the PID resolves: it should also be stable, whether it is a born digital object or a digital representation of a physical or abstract entity.

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A persistent, unique and globally resolvable identifier that is based on an openly specified PID Schema.

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The entity or representation to which the PID resolves.

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Process of resolving or redirecting a PID to some address/page for its denoted item, containing the resource itself or its description or metadata. The PID resolving system/service might pertain specifically to an individual PID type or resolve different PID types, it might operate centrally/globally or comprise a distributed network of resolvers. 

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A PID is resolvable (functional) when it allows both human and machine users to access a digital object, a digital representation, or information on how the object can be accessed. A global resolution system should also support access to Kernel information from its PID. If the object or its representation are no longer available, resolution to Kernel information (a tombstone information) must still be possible. 

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A suffix is the part of a unique and persistent identifier that is created by a local authority (typically PID Manager), which also specifies the syntax rules for the suffix. 

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A value by which an item is unambiguously identified within or outside a particular context or system. It can be a persistent identifier, a local identifier, or sometimes an internal identifier. The identifier that is the main unique identifier of the item in the service is the key identifier.

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A structured record consisting of well-defined attributes to allow machine actions. PIDs resolve to these structured records. (EOSC PID policy 2026)