RKDIconclass is the most widely accepted classification system for describing and retrieving subjects represented in images, from paintings and drawings to photographs and book illustrations. Developed over several decades by the Dutch art historian Henri van de Waal and now maintained by the RKD (Netherlands Institute for Art History), the system provides a shared scientific vocabulary that enables consistent iconographic description across museums, archives, and research institutions worldwide.
Background
Henri van de Waal began developing Iconclass in 1958 at the University of Leiden, motivated by the lack of a systematic tool for classifying the subjects depicted in visual art. The problem he addressed was fundamental: while libraries had long possessed classification schemes for texts, no equivalent existed for the subject content of images. Van de Waal worked on the system for decades; the first volumes were published in the 1970s, and the complete scheme was published posthumously (van de Waal died in 1972) in a seventeen-volume set completed in 1985.
The system was originally published in print and later digitized. It is now maintained by the RKD in The Hague, which hosts the online Iconclass Browser and makes the classification available as Linked Open Data (LOD). The RKD is an institute of the Royal Netherlands Academy of Arts and Sciences.
Purpose and Scope
Iconclass is designed for:
- Indexing and cataloguing the subjects of works of visual art and related imagery
- Enabling subject-based retrieval across image collections
- Supporting art historical research and iconographic studies
- Providing a multilingual classification framework for international collaboration
The scheme covers the full range of subjects found in Western art, including religious and mythological themes, historical events, abstract concepts, everyday life, nature, and portraiture.
Structure
Iconclass is organized into ten main divisions:
| Division | Subject |
|---|---|
| 0 | Abstract, Non-representational Art |
| 1 | Religion and Magic |
| 2 | Nature |
| 3 | Human Being, Man in General |
| 4 | Society, Civilization, Culture |
| 5 | Abstract Ideas and Concepts |
| 6 | History |
| 7 | Bible |
| 8 | Literature |
| 9 | Classical Mythology and Ancient History |
The system comprises three main components:
- Classification System: approximately 28,000 hierarchically ordered definitions, each consisting of an alphanumeric notation (e.g., 73C7211 for the Annunciation to the Shepherds) paired with a textual description (the "textual correlate").
- Alphabetical Index: approximately 14,000 keywords that map to notations, allowing users to find the correct code for a given subject.
- Bibliography: approximately 40,000 references to books and articles of iconographic interest (not yet available online).
The notation uses a combination of digits and letters. Hierarchical depth is expressed by extending the notation: broader concepts have shorter codes, and more specific subjects have longer ones. Bracketed text can be added to notations to describe specific instances (e.g., named persons or places).
Multilingual Access
The Iconclass Browser provides descriptions and keywords in English, German, French, and Italian. Partial translations exist in Finnish and Norwegian, and experimental translations in Chinese and Dutch are in development.
Governance and Maintenance
Iconclass is maintained by the RKD (Netherlands Institute for Art History) in The Hague. The classification is published online through the Iconclass Browser and as Linked Open Data. An active community of users contributes to discussions through a blog and Google Groups forum.
Notable Implementations
Iconclass is used by major museums, libraries, and research institutes for cataloguing their art collections, including the Rijksmuseum, the British Museum, the Warburg Institute, and the Bildarchiv Foto Marburg. It is integrated into collection management systems and is used by the Census of Antique Works of Art and Architecture Known in the Renaissance, among other scholarly projects.
Related Standards
- Art & Architecture Thesaurus (AAT) -- while the AAT provides controlled vocabulary for art description broadly (materials, techniques, styles), Iconclass specifically addresses the subjects and iconographic content depicted in images.