ISO 15511:2019

Overview

ISO 15511:2019 defines the International Standard Identifier for Libraries and related organizations (ISIL). It provides a flexible, globally interoperable identifier scheme to uniquely identify libraries, archives, museums and subordinate administrative units with minimal disruption to existing national systems. ISILs can identify the originator or holder of a resource (e.g., library material or archival collection) and are intended for use by libraries and related organizations and their external partners (suppliers, publishers, government bodies).

Key topics and technical requirements

• Identifier structure: An ISIL consists of three components in this order: a prefix, a hyphen-minus (-) (mandatory), and a unit identifier. When presented visually it is preceded by the label "ISIL ".
• Length and characters: Variable length up to 16 characters. Permitted characters are digits (0–9), letters A–Z / a–z (ISO basic Latin), and the special characters / (solidus), - (hyphen-minus), and : (colon). Diacritics are not allowed.
• Prefix types:
  • Country code: Two uppercase letters per ISO 3166-1 alpha‑2 (e.g., GB, DE). Country-code prefixes are case-insensitive.
  • Non-country code: Registered strings (1, 3, or 4 characters) made of Latin letters or digits (no special marks). These must be registered with the ISIL Registration Authority (e.g., OCLC).
• Uniqueness and normalization: Each ISIL must be unique when normalized according to ISO/IEC 10646 character repertoire. Prefix case-insensitivity contrasts with unit identifier case rules, which may be decided at the national level (e.g., FI-Ht vs FI-HT can be distinct).
• Administrative rules: ISILs are intended to persist for the life of the organization or subordinate unit. Significant administrative changes (merger, name change) may require issuance of a new ISIL. Existing national/local codes may be incorporated into ISILs; multiple ISILs for one organization are possible but discouraged.

Applications and who uses ISO 15511

• Library management systems, union catalogs, discovery layers: to identify holding institutions and originators of records.
• Archives and museum cataloguing: to link collections and provenance to institutions.
• Metadata exchange and linked data: as stable identifiers in MARC, MODS, Dublin Core, RDF and similar contexts.
• Suppliers, publishers, and government agencies: to route orders, rights, and administrative transactions to the correct organization or unit.
• Target users: librarians, archivists, museum registrars, metadata specialists, system vendors, and standards/IT teams.

Related standards

• ISO 3166-1 (country codes)
• ISO/IEC 10646 (character repertoire / Unicode)
• ISO 5127 (terminology for information and documentation)

Practical takeaway: ISO 15511 (ISIL) enables persistent, interoperable organization identifiers across libraries, archives and museums-critical for reliable metadata linking, resource sharing and international collaboration.