Linked Art API Schema: Concept

Last refreshed: 2026-07-06

Source: Concept schema docs and concept.json, part of Linked Art API 1.0, published under CC BY 4.0. This is a project summary; the upstream schema is authoritative.

Purpose

The Concept schema describes `crm:E55_Type`: concepts, subjects, and other categorizations. In Linked Art API terms this covers full concept records, including `Type` and subclasses such as `Language`, `Material`, `Currency`, and `MeasurementUnit`.

Related upstream references:

• Concept API endpoint
• Concept model documentation

Top-Level Constraints

• Schema type: object.
• CRM class: `crm:E55_Type`.
• Additional top-level properties are not allowed.
• `@context`: required.
• `id`: required URI string for the entity.
• `type`: required class string. Practical Linked Art classes include `Type`, `Language`, `Material`, `Currency`, and `MeasurementUnit`.
• `_label`: required developer-facing human-readable label.

Permitted Top-Level Fields

• `classified_as`: array of `Type` structures that classify this concept beyond its class.
• `identified_by`: array of `Name` or `Identifier` structures.
• `referred_to_by`: array of embedded statements or textual references about the concept.
• `equivalent`: array of compact references to equivalent identities in external vocabularies or systems.
• `representation`: array of embedded `VisualItem` structures linked to digital objects.
• `member_of`: array of `Set` references.
• `subject_of`: array of embedded `LinguisticObject` web pages or digital objects focused on this concept.
• `attributed_by`: array of `AttributeAssignment` structures relating another entity to this concept.
• `created_by`: creation activity for the intellectual or conceptual entity.
• `broader`: array of broader concept references, using `skos:broader`.

Embedded Structures Highlighted By The Schema

`classified_as` items are concept references:

• `id`: required.
• `type`: required.
• `_label`, `identified_by`, `classified_as`, `referred_to_by`, and `equivalent` are allowed.

`identified_by` items can be:

• `Name` structures, with required `type` and `content`, plus optional `_label`, nested `identified_by`, `referred_to_by`, `classified_as`, `language`, and `part`.
• `Identifier` structures, following the shared identifier pattern.

`referred_to_by` items are embedded `LinguisticObject` statements:

• `type`: required.
• `content`: required.
• `_label`, `identified_by`, `classified_as`, `referred_to_by`, `language`, and `format` are allowed.

`equivalent` items are compact references:

• `id`: required.
• `type`: required.
• `_label`: optional.
• `equivalent`: optional nested equivalent references.

`representation` items are embedded `VisualItem` structures:

• `type`: required.
• `_label`, `identified_by`, `classified_as`, `referred_to_by`, and `digitally_shown_by` are allowed.
• Nested digital objects can carry `access_point`, `format`, and `conforms_to`.

`subject_of` items are embedded `LinguisticObject` structures:

• `type`: required.
• `_label`, `identified_by`, `classified_as`, `referred_to_by`, `language`, and `digitally_carried_by` are allowed.

`broader` items reference a `Type` or subclass:

• Broader links model concept hierarchy and should remain explicit `skos:broader` relationships.
• Subclasses can include `Language`, `Material`, `Currency`, and `MeasurementUnit`.

Creation Activity Shape

`created_by` describes creation of the concept record or conceptual entity. The expanded schema allows normal activity fields:

• `type`
• `_label`
• `identified_by`
• `classified_as`
• `referred_to_by`
• `took_place_at`
• `timespan`
• `caused_by`
• `carried_out_by`
• `used_specific_object`
• `influenced_by`
• `technique`
• `during`
• `after`
• `before`
• `part_of`

`part_of` can reference an `Event` or `Activity` with required `id` and `type`, plus optional `_label` and `equivalent`.

Meta Museum Notes

Meta Museum already preserves concept classes, vocabulary alignments, `equivalent` links, `notation`, and `broader` relationships in the Concept endpoint notes and shared concept-reference notes. This expanded schema adds the strict endpoint validation target: concept records are full `crm:E55_Type` objects with required identity/label fields and no unexpected top-level properties.

The highest-value next code task is to validate representative `Type`, `Material`, `Language`, `Currency`, and `MeasurementUnit` records against `concept.json`, including `broader` hierarchy and embedded statement language/format fields.

Test Ideas

• Validate representative Concept records against `concept.json`.
• Assert `@context`, `id`, `type`, and `_label` are present.
• Assert unknown top-level properties fail schema validation.
• Preserve `broader` as explicit concept hierarchy, not a flattened label.
• Preserve `representation` visual evidence and `subject_of` web-page evidence.
• Preserve `created_by` activity fields including `timespan`, `carried_out_by`, `used_specific_object`, `technique`, and `part_of`.