# Globally unique, persistent and resolvable identifier schemas

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This feature is in active development.
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The attribute that marks a record as a GUPRI within the "Additional Information" tab is applicable to our **identifier schema records only**.
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FAIRsharing allows the registration of any community-relevant persistent identifiers (PIDs), whether or not they are also globally-unique and resolvable (a.k.a. GUPRIs, see our section on [identifier schema records](https://fairsharing.gitbook.io/fairsharing/record-sections-and-fields/general-information/registry-type#additional-information-regarding-identifier-schema-records)). FAIRsharing simplifies the EOSC PID Policy to determine if an identifier schema is also a GUPRI:

> A Persistent Identifier (PID) policy for the European Open Science Cloud (EOSC), Publications Office, 2020, <https://data.europa.eu/doi/10.2777/926037>

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If your identifier schema is a GUPRIs as defined below, then enable the tickbox within the Additional Information tab that asks "Is this identifier schema a [GUPRI](https://fairsharing.gitbook.io/fairsharing/additional-information/globally-unique-persistent-and-resolvable-identifier-schemas) as defined by FAIRsharing?".
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## How do I tell if my identifier schema conforms to the FAIRsharing GUPRI policy?

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Remember that, as long as it fits within [our scope](https://fairsharing.gitbook.io/fairsharing/record-sections-and-fields/general-information/registry-type#additional-information-regarding-identifier-schema-records), you can still register your identifier schema with us even if it does not conform to the FAIRsharing GUPRI policy as interpreted and summarised below.
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While the requirements for being a FAIRsharing GUPRI are closely aligned with the EOSC PID policy document linked above, there are some differences. Firstly, some aspects of the EOSC PID policy are beyond the scope of the curation team to assess; as such, some attributes defined as mandatory by EOSC may be optional for FAIRsharing to provide flexibility with regards to what is publicly available for these standards. Secondly, some aspects of the EOSC PID policy are not appropriate to a globally-relevant resource such as FAIRsharing. For example, FAIRsharing does not require or check that an identifier schema integrates with the European Research Infrastructures (EOSC PID 7.1).

The following conditions must be met for your identifier schema to be considered globally unique, persistent and resolvable as per FAIRsharing requirements. The identifier schema:

1. **should** be mature, and the id providers should show a commitment to sustaining the infrastructures and the minted identifiers for the long term (similar to EOSC PID policy principles 2.7 and 2.8).
2. **must** be globally unique, persistent, and resolvable (similar to EOSC PID section 3).
   1. Global uniqueness: **must** use a controlled syntax/namespaces to avoid clashes.
   2. Persistence : **Must** have clear community backing for the schema. The syntax of the schema **must** be stable. The referred object **should** itself be stable, though there are various ways to show this (e.g., a dataset might be completely immutable, while a record describing an organisation is likely to change as the organisations homepage, name or other attributes change).
   3. Resolvable: humans and machines **must** be able to use the identifier to access information on the digital object, how the object can be accessed, or the object itself. There **should** be an established tombstoning or equivalent procedure.
3. It **must** be clear who the maintaining organisation for the identifier schema is (similar to EOSC PID 5.3).
4. There **should** be a clear preservation policy / exit plan, should the original provider shut down (similar to EOSC PID 8.4).
