Irretrievability

Irretrievability refers to the state in which information cannot be retrieved by a retrieval system, even when the item exists within a data source. It is a concern in information retrieval, digital preservation, and data management, and contrasts with retrievability.

Common causes include data degradation (bit rot, corruption), outdated or missing metadata, obsolescence of formats, incomplete or poorly indexed collections, access controls, legal or policy restrictions, and encryption without available keys.

The result is reduced findability, impaired access, and fragmentation of knowledge. For search engines and repositories, irretrievability can undermine user trust, hinder compliance, and complicate audits.

In practice, addressing irretrievability involves digital preservation practices: regular data integrity checks, format migration, comprehensive metadata, persistent identifiers, robust indexing, and preservation of access credentials.

Examples include a database after schema changes that prevents old queries, a website blocked to crawlers, or an encrypted file for which the decryption key is lost.