ISO 19126:2021

Overview

ISO 19126:2021 - "Geographic information - Feature concept dictionaries and registers" defines a standardized schema for creating, managing and registering feature concept dictionaries used in geographic information systems (GIS). The standard specifies how dictionaries are structured and how they can be managed as registers, including a hierarchical register that links feature concept dictionaries and derived feature catalogues. It explicitly aligns register management with ISO 19135‑1. ISO 19126 does not prescribe schemas for feature catalogues themselves, but supports their derivation from concept dictionaries.

Key topics and technical requirements

• Schema for feature concept dictionaries: Detailed model elements for dictionary objects (for example, CD_FeatureConceptDictionary, CD_Concept, CD_FeaturePropertyConcept, CD_NominalValueConcept) and how they relate.
• Concept relationships and types: Definitions for concept relationships (CD_ConceptRelationship, CD_ConceptRelationshipType) and code values to express semantic links.
• Scope and packages: Mechanisms to define scope (CD_Scope) and package/grouping semantics for organizing concepts.
• Register management: Rules for managing dictionaries as registers, including item classes for concepts, attributes, nominal values, associations and operations, and registration workflows.
• Hierarchical register model: Schema for a hierarchical register that describes and links subregisters of feature concept dictionaries and feature catalogues (e.g., HR_FeatureInformationSubregisterDescription, HR_FeatureInfoSubRegisterType).
• Conformance and testing: Clauses on conformance, conformance for dictionaries/registers and a normative abstract test suite (Annex A) plus information for registration proposals (Annex B).
• Governance and metadata alignment: Guidance to ensure registers adhere to ISO 19135‑1 rules for registration and governance.

Applications and who should use it

ISO 19126 is practical for organizations that need consistent, machine-readable definitions of geographic features to enable interoperability and reuse:

• National mapping and cadastral agencies creating authoritative feature dictionaries
• Spatial Data Infrastructure (SDI) stewards and registry managers implementing governed registers
• GIS data modelers and standards teams producing harmonized feature catalogues
• Software vendors and developers building tools for cataloguing, validation, and semantic integration
• Data publishers and integrators needing consistent feature semantics across datasets and services

Benefits include improved semantic interoperability, reduced ambiguity in feature definitions, and a standardized approach to registering and discovering feature definitions.

Related standards

• ISO 19135‑1 (registers) - referenced for register management and conformance
• Other ISO geographic information standards (used together with ISO 19126 for end‑to‑end interoperability and cataloguing)

Keywords: ISO 19126, feature concept dictionaries, feature catalogues, geographic information, registers, ISO 19135-1, GIS interoperability, spatial data infrastructure, metadata, schema.