A convention of the ARK identifier scheme whereby appending a single '?' to an ARK URL yields the object's descriptive metadata and appending '??' yields a 'commitment statement' describing the issuing institution's persistence policy for that ARK.

ByCASRAI Editorial Board

· Last updated 10 Jul 2026

Examples

Worked examples

Is an instance
https://n2t.net/ark:/12345/x54xz321? returning Dublin Core metadata for the object.
Is an instance
https://n2t.net/ark:/12345/x54xz321?? returning a persistence policy statement.

Counter-examples

Looks similar, but isn't

Not an instance
A DOI does not support the '?' or '??' inflections in the ARK sense.
Not an instance
A URL with a query string '?lang=fr' is not an ARK inflection.

Editorial commentary

Inflections are a distinctive design choice of ARK that separates an identifier from its ‘inflected’ metadata views without minting separate identifiers. The single-question-mark inflection is intended for machine-readable metadata; the double-question-mark inflection is intended for human-readable persistence commitments. ARK-conforming resolvers honour these inflections by serving the appropriate response for the underlying object.

References

Kunze J., Rodgers R., 'The ARK Identifier Scheme', IETF Internet-Draft.

Also known as

ARK ? and ?? convention

Machine-readable encodings

Use in your systems

JATS XML <role> element

xml

<role vocab="credit"
      vocab-identifier="https://casrai.org/dictionary/"
      vocab-term="ARK inflection rules"
      vocab-term-identifier="https://casrai.org/dictionary/term/ark-inflection-rules" />

Schema.org DefinedTerm (JSON-LD)

json

{
  "@context": "https://schema.org",
  "@type": "DefinedTerm",
  "@id": "https://casrai.org/dictionary/term/ark-inflection-rules",
  "name": "ARK inflection rules",
  "identifier": "https://casrai.org/dictionary/term/ark-inflection-rules",
  "description": "A convention of the ARK identifier scheme whereby appending a single '?' to an ARK URL yields the object's descriptive metadata and appending '??' yields a 'commitment statement' describing the issuing institution's persistence policy for that ARK.",
  "inDefinedTermSet": "https://casrai.org/dictionary/domain/persistent-identifiers#set",
  "url": "https://casrai.org/dictionary/term/ark-inflection-rules",
  "sameAs": [
    "ARK ? and ?? convention"
  ],
  "license": "https://creativecommons.org/licenses/by/4.0/",
  "publisher": {
    "@id": "https://casrai.org/#organization"
  },
  "dateModified": "2026-07-10T02:06:20",
  "inLanguage": "en"
}

Referenced across the research world

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