ISO/IEC 9594-6:2020

Overview

ISO/IEC 9594-6:2020 - titled Information technology - Open systems interconnection - Part 6: The Directory: Selected attribute types - standardizes a core set of Directory attribute types, syntaxes and matching rules used when building and querying directory services. Prepared in conjunction with ITU‑T (as X.520) and forming part of the ISO/IEC 9594 series, this ninth edition defines attribute categories, string preparation rules, matching behaviour and an ASN.1 module (Annex A) for interoperable Directory implementations and profiles.

Key topics and technical requirements

This standard focuses on practical directory semantics and interoperability. Major technical topics include:

• Selected attribute types across many categories: system, labelling, geographical, organizational, postal addressing, telecommunications, preferences, OSI application, relational, domain, hierarchical, and more.
• Matching rules for comparing attribute values: string matching, syntax‑based, time, first component, word, approximate, zonal, identity and password‑policy related matching.
• Syntaxes and string preparation: rules for transcode, map, normalize, prohibit, bidirectional checks and insignificant character removal to ensure consistent comparisons.
• Contexts and options: language, temporal, locale contexts and LDAP attribute option contexts to support localized and context‑sensitive behaviour.
• Security and authentication attributes: simple authentication attributes, password policy attributes and notification attributes.
• ASN.1 module and mappings: complete ASN.1 notation in Annex A and examples for name mapping (Object Identifiers, URNs) in Annexes F–G.

Important recommendations:

• Prefer using the standardized attribute types and matching rules defined here rather than inventing new ones.
• Administrative authorities may define local attribute types, but these are not internationally standardized and require bilateral agreements for external use.

Practical applications and who uses it

ISO/IEC 9594-6:2020 is essential for:

• Directory implementers and vendors (LDAP/Directory servers) ensuring interoperability and correct attribute comparisons.
• Identity and access management (IAM) architects defining attribute schemas and password policies.
• Enterprise architects and network engineers building federated directories or cross‑organizational directory integrations.
• Standards bodies and industry forums creating domain‑specific directory profiles based on this foundational framework.

Practical benefits include consistent search and matching behaviour, reduced schema fragmentation, and a clear base for building application‑specific directory profiles.

Related standards

• ITU‑T X.520 (equivalent text) and other parts of the ISO/IEC 9594 series (e.g., X.521 / ISO/IEC 9594-7 for object classes and naming).
• LDAP and related IETF directory specifications for deployment contexts.

Keywords: ISO/IEC 9594-6, Directory attribute types, matching rules, DIB, LDAP, ASN.1, Open Systems Interconnection, directory syntaxes, string preparation.