glam/docs/ONTOLOGY_INTEGRATION.md

# GHCID Ontology Integration Guide

**Version**: 1.0  
**Date**: 2025-11-06  
**Schema Version**: v0.2.0 (modular)

---

## Table of Contents

1. [Introduction](#introduction)
2. [Ontology Landscape](#ontology-landscape)
3. [CIDOC-CRM Integration](#cidoc-crm-integration)
4. [RiC-O Integration](#ric-o-integration)
5. [Schema.org Integration](#schemaorg-integration)
6. [EU Core Public Organization Vocabulary (CPOV)](#eu-core-public-organization-vocabulary-cpov)
7. [Dutch TOOI Ontology](#dutch-tooi-ontology)
8. [W3C Organization Ontology](#w3c-organization-ontology)
9. [PROV-O Integration](#prov-o-integration)
10. [Comprehensive Mapping Table](#comprehensive-mapping-table)
11. [RDF Serialization Examples](#rdf-serialization-examples)
12. [Gap Analysis](#gap-analysis)
13. [Implementation Recommendations](#implementation-recommendations)

---

## Introduction

### Purpose

This document provides a comprehensive guide to integrating the **Global Heritage Custodian Identifier (GHCID)** schema with established heritage, archival, and organizational ontologies. The GHCID schema is designed to be **interoperable** with existing Linked Data standards while providing unique capabilities for persistent identification and change tracking across heritage institutions worldwide.

### Scope

The GHCID project integrates with **seven major ontologies**:

1. **CIDOC Conceptual Reference Model (CIDOC-CRM) v7.1.3** - Museum and cultural heritage domain
2. **Records in Contexts Ontology (RiC-O) v1.1** - International archival standard
3. **Schema.org** - Web discoverability and SEO
4. **EU Core Public Organization Vocabulary (CPOV)** - European public sector organizations
5. **Dutch TOOI Ontology** - Netherlands government organizations
6. **W3C Organization Ontology (ORG)** - Generic organizational structures
7. **W3C PROV Ontology (PROV-O)** - Provenance and data lineage

### Integration Philosophy

The GHCID schema follows these principles:

- **Alignment over Replacement**: Map GHCID concepts to ontology equivalents using `owl:equivalentClass` and `rdfs:subClassOf`
- **Selective Extension**: Add GHCID-specific capabilities (persistent IDs, change history) as extensions
- **Multi-Ontology Compatibility**: Support multiple ontologies simultaneously (e.g., a museum can be both `cidoc:E74_Group` and `schema:Museum`)
- **Namespace Preservation**: Preserve original ontology namespaces in RDF serialization
- **Practical Interoperability**: Focus on real-world use cases (data exchange, aggregation, discovery)

---

## Ontology Landscape

### File Locations

All ontology files are stored in `/data/ontology/`:

```
data/ontology/
├── CIDOC_CRM_v7.1.3.rdf          # CIDOC-CRM OWL/RDF (948 lines)
├── RiC-O_1-1.rdf                  # RiC-O OWL/RDF (16,795 lines)
├── schemaorg.owl                  # Schema.org OWL (2.7 MB)
├── core-public-organisation-ap.ttl # CPOV Turtle (600+ lines)
├── tooiont.ttl                    # TOOI Turtle (Dutch gov)
├── org.ttl                        # W3C ORG Ontology
└── prov-o.ttl                     # W3C PROV-O
```

### Namespace Prefixes

```turtle
@prefix ghcid:   <https://w3id.org/heritage/custodian/> .
@prefix cidoc:   <http://www.cidoc-crm.org/cidoc-crm/> .
@prefix rico:    <https://www.ica.org/standards/RiC/ontology#> .
@prefix schema:  <http://schema.org/> .
@prefix cpov:    <http://data.europa.eu/m8g/> .
@prefix tooi: <https://identifier.overheid.nl/tooi/def/ont/> .
@prefix org:     <http://www.w3.org/ns/org#> .
@prefix prov:    <http://www.w3.org/ns/prov#> .
@prefix owl:     <http://www.w3.org/2002/07/owl#> .
@prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos:    <http://www.w3.org/2004/02/skos/core#> .
```

---

## CIDOC-CRM Integration

### Overview

**CIDOC Conceptual Reference Model (CIDOC-CRM)** is the **ISO 21127:2014** standard for cultural heritage information. It provides a formal ontology for museum documentation, collection management, and heritage data integration.

**Specification**: `data/ontology/CIDOC_CRM_v7.1.3.rdf`  
**Namespace**: `http://www.cidoc-crm.org/cidoc-crm/`  
**Relevance**: Essential for museums, galleries, and cultural heritage institutions.

### Key CIDOC-CRM Classes

| CIDOC-CRM Class | Description | GHCID Mapping |
|-----------------|-------------|---------------|
| `E39_Actor` | Agents (people or groups) capable of actions | `HeritageCustodian` (superclass) |
| `E74_Group` | Organized collectives with identity | `HeritageCustodian` (primary mapping) |
| `E5_Event` | Changes of state in physical/conceptual items | `ChangeEvent` |
| `E78_Curated_Holding` | Collections assembled and managed | `Collection` |
| `E53_Place` | Geographic locations | `Location` |
| `E42_Identifier` | Identifiers assigned to entities | `Identifier` |

### Class Alignments

#### HeritageCustodian → E74_Group

```turtle
ghcid:HeritageCustodian
  rdfs:subClassOf cidoc:E74_Group ;
  owl:equivalentClass cidoc:E74_Group ;
  rdfs:label "Heritage Custodian Organization"@en ;
  rdfs:comment "A heritage institution (museum, library, archive, etc.) that holds and manages cultural heritage collections. Modeled as a CIDOC-CRM Group (E74) to enable integration with museum documentation standards."@en .
```

**Rationale**:
- `E74_Group` represents organizations with collective identity and purpose
- `E74` is subclass of `E39_Actor`, enabling participation in events (E5)
- Museums, libraries, and archives fit the definition of "social entities" in CIDOC-CRM

#### ChangeEvent → E5_Event

```turtle
ghcid:ChangeEvent
  rdfs:subClassOf cidoc:E5_Event ;
  rdfs:label "Organizational Change Event"@en ;
  rdfs:comment "Significant organizational changes (mergers, relocations, closures, etc.) modeled as CIDOC-CRM Events (E5) to track temporal evolution of heritage institutions."@en .
```

**Properties**:
- `cidoc:P4_has_time-span` → `ChangeEvent.event_date`
- `cidoc:P14_carried_out_by` → Participating organizations
- `cidoc:P16_used_specific_object` → Affected organizations

#### Collection → E78_Curated_Holding

```turtle
ghcid:Collection
  rdfs:subClassOf cidoc:E78_Curated_Holding ;
  rdfs:label "Heritage Collection"@en .
```

### Property Mappings

| GHCID Property | CIDOC-CRM Property | Range |
|----------------|-------------------|-------|
| `name` | `P1_is_identified_by` + `E41_Appellation` | String |
| `description` | `P3_has_note` | String |
| `locations` | `P74_has_current_or_former_residence` | `E53_Place` |
| `identifiers` | `P1_is_identified_by` | `E42_Identifier` |
| `change_history` | `P11i_participated_in` | `E5_Event` |

### CIDOC-CRM Benefits

1. **ISO Standard Compliance**: Enables interoperability with museum sector systems
2. **Event Modeling**: Rich temporal modeling for organizational changes
3. **Collection Integration**: Direct mapping to collection management standards
4. **Property Graph**: Detailed relationship tracking via CIDOC properties
5. **Time-Span Support**: Better temporal granularity than ISO 8601 dates

### Limitations

- **Complexity**: CIDOC-CRM's 90+ classes can be overwhelming
- **Museum-Centric**: Less tailored for libraries and archives (use RiC-O for those)
- **Learning Curve**: Requires expertise in cultural heritage documentation

---

## RiC-O Integration

### Overview

**Records in Contexts Ontology (RiC-O)** is the official ontology of the **International Council on Archives (ICA)**. It replaces older archival standards (ISAD(G), ISAAR(CPF)) with a modern Linked Data approach.

**Specification**: `data/ontology/RiC-O_1-1.rdf` (16,795 lines!)  
**Namespace**: `https://www.ica.org/standards/RiC/ontology#`  
**Relevance**: **CRITICAL** for archives and archival institutions.

### Why RiC-O Matters for GHCID

RiC-O is **the most important ontology** for the archival sector:

1. **International Standard**: Endorsed by ICA, used globally
2. **Rich Provenance**: Extensive provenance modeling aligned with archival principles
3. **Relationship-Centric**: Models complex organizational relationships (predecessors, successors, hierarchies)
4. **Archival Description**: Purpose-built for describing archival records and their custodians
5. **Change Tracking**: Native support for organizational change events

### Key RiC-O Classes

| RiC-O Class | Description | GHCID Mapping |
|-------------|-------------|---------------|
| `rico:Agent` | Entities capable of actions | `HeritageCustodian` (superclass) |
| `rico:CorporateBody` | Organizations and institutions | `HeritageCustodian` (primary) |
| `rico:RecordResource` | Records and record sets | `Collection` |
| `rico:Record` | Individual records | `DigitalObject` |
| `rico:RecordSet` | Groups of records | `Collection` |
| `rico:Activity` | Actions performed by agents | `ChangeEvent` |
| `rico:Place` | Geographic locations | `Location` |
| `rico:Identifier` | Identifiers | `Identifier` |

### Class Alignments

#### HeritageCustodian → rico:CorporateBody

```turtle
ghcid:HeritageCustodian
  rdfs:subClassOf rico:CorporateBody ;
  owl:equivalentClass rico:CorporateBody ;
  rdfs:label "Heritage Custodian Organization"@en ;
  rdfs:comment "An archival institution, library, or museum modeled as a RiC-O Corporate Body to align with international archival standards (ICA RiC-O)."@en .
```

**Rationale**:
- Archives ARE corporate bodies in RiC-O terminology
- `rico:CorporateBody` supports organizational change tracking
- Aligns with archival description practices worldwide

#### ChangeEvent → rico:Activity

```turtle
ghcid:ChangeEvent
  rdfs:subClassOf rico:Activity ;
  rdfs:label "Organizational Change Activity"@en ;
  rdfs:comment "Organizational changes (mergers, splits, relocations) modeled as RiC-O Activities to track archival institution evolution over time."@en .
```

**Properties**:
- `rico:hasBeginningDate` → `ChangeEvent.event_date`
- `rico:hasEndDate` → End of event (optional)
- `rico:hasActivityType` → Maps to `ChangeTypeEnum`
- `rico:agentAssociatedWithActivity` → Participating organizations

### Property Mappings

| GHCID Property | RiC-O Property | Notes |
|----------------|---------------|-------|
| `name` | `rico:hasOrHadName` + `rico:Name` | Use rico:Name class for structured names |
| `alternative_names` | `rico:hasOrHadOtherName` | Multiple alternative names |
| `description` | `rico:scopeAndContent` | Archival description field |
| `institution_type` | `rico:hasOrganizationType` | Maps to institution type taxonomy |
| `locations` | `rico:hasOrHadLocation` | Links to `rico:Place` |
| `identifiers` | `rico:hasOrHadIdentifier` | Links to `rico:Identifier` |
| `change_history` | `rico:history` | Narrative history field |
| `change_history` (events) | `rico:agentIsTargetOfActivity` | Link to `rico:Activity` |

### Advanced RiC-O Features

#### Predecessor/Successor Relationships

RiC-O excels at modeling organizational lineage:

```turtle
# Example: Merger creating Noord-Hollands Archief (2001)
ghcid:nl-haarhaarlem rdfs:label "Gemeentearchief Haarlem" ;
  rico:hasSuccessor ghcid:nl-haarnha ;
  rico:agentIsTargetOfActivity ghcid:event-nha-merger-2001 .

ghcid:nl-haarrijks rdfs:label "Rijksarchief in Noord-Holland" ;
  rico:hasSuccessor ghcid:nl-haarnha ;
  rico:agentIsTargetOfActivity ghcid:event-nha-merger-2001 .

ghcid:nl-haarnha rdfs:label "Noord-Hollands Archief" ;
  rico:hasPredecessor ghcid:nl-haarhaarlem, ghcid:nl-haarrijks ;
  rico:beginningDate "2001-01-01"^^xsd:date .

ghcid:event-nha-merger-2001 a rico:Activity, ghcid:ChangeEvent ;
  rico:hasActivityType ghcid:MERGER ;
  rico:hasBeginningDate "2001-01-01"^^xsd:date ;
  rico:agentAssociatedWithActivity ghcid:nl-haarhaarlem, ghcid:nl-haarrijks, ghcid:nl-haarnha .
```

#### Archival Holdings

Link heritage custodians to their collections:

```turtle
ghcid:nl-haarnha
  rico:hasOrHadCustody ghcid:collection-haarlem-city-records ;
  rico:isOrWasAuthorityOf ghcid:collection-haarlem-city-records .

ghcid:collection-haarlem-city-records a rico:RecordSet, ghcid:Collection ;
  rico:scopeAndContent "Municipal records of Haarlem, 1245-present" ;
  rico:hasProvenance ghcid:nl-haarhaarlem .
```

### RiC-O Benefits for GHCID

1. **Archival Authority**: ICA-endorsed standard, widely adopted
2. **Change Tracking**: Native support for organizational evolution
3. **Relationship Modeling**: Predecessor/successor, parent/child, partner relationships
4. **Provenance Integration**: Aligns with archival provenance principles
5. **Global Adoption**: Used by national archives worldwide (France, UK, Netherlands, etc.)

### Implementation Priority

**HIGH PRIORITY**: For any GHCID instance involving archives, RiC-O alignment is **mandatory**.

---

## Schema.org Integration

### Overview

**Schema.org** is the de facto standard for structured data markup on the web. It enables search engines (Google, Bing) to understand and display rich results for heritage institutions.

**Specification**: `data/ontology/schemaorg.owl` (2.7 MB)  
**Namespace**: `http://schema.org/`  
**Relevance**: Essential for web discoverability and SEO.

### GLAM-Specific Schema.org Classes

Schema.org has **dedicated classes** for GLAM institutions:

| Schema.org Class | Description | GHCID Mapping |
|------------------|-------------|---------------|
| `schema:Museum` | Museum organizations | `InstitutionTypeEnum.MUSEUM` |
| `schema:Library` | Library organizations | `InstitutionTypeEnum.LIBRARY` |
| `schema:ArchiveOrganization` | Archival institutions | `InstitutionTypeEnum.ARCHIVE` |
| `schema:ArchiveComponent` | Archival collections | `Collection` |
| `schema:LibrarySystem` | Multi-branch library systems | Parent organizations |

### Class Alignments

#### Institution Type Mapping

```turtle
# When institution_type = MUSEUM
ghcid:rijksmuseum a schema:Museum, ghcid:HeritageCustodian ;
  schema:name "Rijksmuseum" ;
  schema:location [ a schema:Place ; schema:addressCountry "NL" ] ;
  schema:url "https://www.rijksmuseum.nl" .

# When institution_type = LIBRARY
ghcid:kb-nl a schema:Library, ghcid:HeritageCustodian ;
  schema:name "Koninklijke Bibliotheek" ;
  schema:description "National Library of the Netherlands" .

# When institution_type = ARCHIVE
ghcid:nl-haarnha a schema:ArchiveOrganization, ghcid:HeritageCustodian ;
  schema:name "Noord-Hollands Archief" ;
  schema:archiveHeld ghcid:collection-haarlem-city-records .
```

#### Collection Mapping

```turtle
ghcid:collection-haarlem-city-records a schema:ArchiveComponent, ghcid:Collection ;
  schema:name "Municipal Records of Haarlem" ;
  schema:dateCreated "1245" ;
  schema:temporalCoverage "1245/2025" ;
  schema:about schema:HistoricalEvent ;
  schema:archivedAt ghcid:nl-haarnha .
```

### Property Mappings

| GHCID Property | Schema.org Property | Notes |
|----------------|-------------------|-------|
| `name` | `schema:name` | Plain string |
| `alternative_names` | `schema:alternateName` | Multiple values allowed |
| `description` | `schema:description` | SEO-optimized description |
| `locations.city` | `schema:location` + `schema:address` | Use `schema:PostalAddress` |
| `identifiers` (URL) | `schema:url` | Official website |
| `identifiers` (Wikidata) | `schema:sameAs` | Link to Wikidata entity |
| `digital_platforms.platform_url` | `schema:url` or `schema:mainEntityOfPage` | Digital presence |
| `collections` | `schema:archiveHeld` (archives) | For archival holdings |

### SEO Benefits

Schema.org markup enables **Google Knowledge Graph** integration:

```html
<!-- JSON-LD for Rijksmuseum webpage -->
<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Museum",
  "@id": "https://w3id.org/heritage/custodian/nl/amsnl-rms",
  "name": "Rijksmuseum",
  "alternateName": "Rijksmuseum Amsterdam",
  "description": "The Rijksmuseum is the national museum of the Netherlands, dedicated to Dutch arts and history.",
  "url": "https://www.rijksmuseum.nl",
  "image": "https://www.rijksmuseum.nl/assets/logo.jpg",
  "address": {
    "@type": "PostalAddress",
    "streetAddress": "Museumstraat 1",
    "addressLocality": "Amsterdam",
    "postalCode": "1071 XX",
    "addressCountry": "NL"
  },
  "sameAs": [
    "https://www.wikidata.org/wiki/Q190804",
    "https://viaf.org/viaf/131511535"
  ],
  "openingHoursSpecification": { ... },
  "hasOfferCatalog": { ... }
}
</script>
```

### Implementation Recommendations

1. **Export JSON-LD**: Generate Schema.org JSON-LD for each institution
2. **Website Embedding**: Provide embeddable snippets for institutional websites
3. **Aggregator Support**: Use Schema.org in aggregation platforms (Europeana, DPLA)
4. **Discovery APIs**: Expose Schema.org via JSON-LD API endpoint

---

## EU Core Public Organization Vocabulary (CPOV)

### Overview

**EU Core Public Organization Vocabulary (CPOV)** is the European standard for describing public sector organizations and services.

**Specification**: `data/ontology/core-public-organisation-ap.ttl`  
**Namespace**: `http://data.europa.eu/m8g/`  
**Relevance**: Important for **government-funded** heritage institutions in EU member states.

### Integration Status

**ALREADY INTEGRATED** in `schemas/core.yaml:106`:

```yaml
# From schemas/core.yaml
class_uri: cpov:ContactPoint  # EU Core Public Organization Vocabulary
```

### Key CPOV Classes

| CPOV Class | Description | GHCID Usage |
|------------|-------------|-------------|
| `cpov:PublicOrganisation` | Government or public sector organization | Many heritage institutions |
| `cpov:ContactPoint` | Contact information | `HeritageCustodian` contact details |
| `cpov:ReferenceFramework` | Legal/regulatory frameworks | Governance metadata |

### Property Mappings

| GHCID Property | CPOV Property | Notes |
|----------------|--------------|-------|
| `name` | `skos:prefLabel` | Preferred label |
| `alternative_names` | `skos:altLabel` | Alternative labels |
| `description` | `dct:description` | Dublin Core Terms |
| `locations` | `locn:location` | ISA Core Location Vocabulary |
| `identifiers` | `dct:identifier` | Dublin Core identifier |

### Use Cases

1. **EU Aggregation**: Interoperability with EU data portals (data.europa.eu)
2. **Public Sector Reporting**: Compliance with EU data standards
3. **Cross-Border Discovery**: Facilitate EU-wide heritage discovery
4. **Funding Compliance**: Align with EU funding requirements (Horizon Europe, etc.)

---

## Dutch TOOI Ontology

### Overview

**TOOI (Thesaurus en Ontologie Overheidsinformatie)** is the Dutch government's ontology for public sector organizations and administrative structures.

**Specification**: `data/ontology/tooiont.ttl`  
**Namespace**: `https://identifier.overheid.nl/tooi/def/ont/`  
**Relevance**: Essential for **Dutch heritage institutions**, especially government archives.

### Integration Status

**ALREADY INTEGRATED** in `schemas/provenance.yaml:91`:

```yaml
# From schemas/provenance.yaml
ChangeEvent:
  class_uri: tooi:Wijzigingsgebeurtenis  # Dutch government change event ontology
```

### Key TOOI Classes

| TOOI Class | Description | GHCID Mapping |
|------------|-------------|---------------|
| `tooi:Wijzigingsgebeurtenis` | Organizational change event | `ChangeEvent` |
| `tooi:Afsplitsing` | Organizational split | `ChangeTypeEnum.SPLIT` |
| `tooi:ExistentieleWijziging` | Existential change (founding, closure) | `ChangeTypeEnum.FOUNDING`, `CLOSURE` |
| `tooi:BestuurlijkeRuimte` | Administrative territory | `Location` (Dutch regions) |

### Change Event Alignment

TOOI provides **precise Dutch government terminology** for organizational changes:

```turtle
ghcid:event-nha-merger-2001 a tooi:Wijzigingsgebeurtenis, ghcid:ChangeEvent ;
  tooi:wijzigingsdatum "2001-01-01"^^xsd:date ;
  tooi:wijzigingstype ghcid:MERGER ;
  tooi:betrokkenOrganisatie ghcid:nl-haarhaarlem, ghcid:nl-haarrijks, ghcid:nl-haarnha .
```

### Benefits for Dutch Institutions

1. **National Standard**: Official Dutch government ontology
2. **Legal Compliance**: Aligns with Dutch administrative law
3. **Provincial Archives**: Essential for provincial and municipal archive integration
4. **Change Tracking**: Precise terminology for Dutch government reorganizations
5. **Linked Open Data**: Integration with Dutch LOD infrastructure (data.overheid.nl)

### Implementation

Use TOOI for all **Dutch government heritage institutions**:
- Provincial archives (e.g., Noord-Hollands Archief, Gelders Archief)
- Municipal archives (e.g., Stadsarchief Amsterdam)
- National archives (Nationaal Archief)
- Government-funded museums and libraries

---

## W3C Organization Ontology

### Overview

**W3C Organization Ontology (ORG)** is a generic ontology for organizational structures, hierarchies, and relationships.

**Specification**: `data/ontology/org.ttl`  
**Namespace**: `http://www.w3.org/ns/org#`  
**Relevance**: Foundation for organizational modeling.

### Integration Status

**ALREADY INTEGRATED** in `schemas/core.yaml`:

```yaml
# From schemas/core.yaml
HeritageCustodian:
  class_uri: org:Organization  # W3C Organization Ontology
  mixins:
    - org:OrganizationalUnit  # For sub-units and departments
```

### Key ORG Classes

| ORG Class | Description | GHCID Mapping |
|-----------|-------------|---------------|
| `org:Organization` | Generic organization | `HeritageCustodian` |
| `org:OrganizationalUnit` | Department or sub-unit | Branch libraries, museum departments |
| `org:Site` | Physical location | `Location` |
| `org:Post` | Job or role | Staff roles (optional) |

### Property Mappings

| GHCID Property | ORG Property | Notes |
|----------------|-------------|-------|
| `name` | `skos:prefLabel` | Organization name |
| `description` | `dct:description` | Organization description |
| `locations` | `org:hasSite` | Links to `org:Site` |
| Parent organization | `org:subOrganizationOf` | Hierarchical relationships |
| Sub-units | `org:hasSubOrganization` | Departments, branches |

### Use Cases

1. **Hierarchical Structures**: Model multi-branch library systems
2. **Museum Departments**: Represent departments within large museums
3. **Archive Networks**: Model provincial/municipal archive relationships
4. **Generic Interoperability**: Broadest possible compatibility

---

## PROV-O Integration

### Overview

**W3C PROV Ontology (PROV-O)** is the standard for provenance and data lineage tracking.

**Specification**: `data/ontology/prov-o.ttl`  
**Namespace**: `http://www.w3.org/ns/prov#`  
**Relevance**: Critical for **data quality** and **provenance tracking**.

### Integration Status

**ALREADY INTEGRATED** across multiple schema modules.

### Key PROV-O Classes

| PROV-O Class | Description | GHCID Mapping |
|--------------|-------------|---------------|
| `prov:Entity` | Data entities | `HeritageCustodian`, `Collection`, etc. |
| `prov:Activity` | Activities that generate/modify entities | `ChangeEvent`, extraction processes |
| `prov:Agent` | Agents responsible for activities | Data creators, extractors |

### Property Mappings

| GHCID Property | PROV-O Property | Notes |
|----------------|----------------|-------|
| `provenance.data_source` | `prov:hadPrimarySource` | Source of data |
| `provenance.extraction_date` | `prov:generatedAtTime` | When data was extracted |
| `provenance.extraction_method` | `prov:wasGeneratedBy` | Extraction process |
| `change_history` | `prov:wasInfluencedBy` | Organizational changes |

### Provenance Graph Example

```turtle
# GHCID record as PROV Entity
ghcid:nl-haarnha a prov:Entity, ghcid:HeritageCustodian ;
  prov:wasGeneratedBy ghcid:extraction-activity-20251106 ;
  prov:hadPrimarySource <https://www.noord-hollandsarchief.nl> ;
  prov:generatedAtTime "2025-11-06T10:30:00Z"^^xsd:dateTime .

# Extraction activity
ghcid:extraction-activity-20251106 a prov:Activity ;
  prov:wasAssociatedWith ghcid:agent-opencode ;
  prov:used <file:///data/ISIL-codes_2025-08-01.csv> ;
  prov:endedAtTime "2025-11-06T10:30:00Z"^^xsd:dateTime .

# Data source
<file:///data/ISIL-codes_2025-08-01.csv> a prov:Entity ;
  prov:wasAttributedTo <https://www.kb.nl/isil> ;
  prov:generatedAtTime "2025-08-01T00:00:00Z"^^xsd:dateTime .
```

### Benefits

1. **Data Quality**: Track data lineage from source to publication
2. **Reproducibility**: Document extraction methods and tools
3. **Trust**: Demonstrate data provenance to users
4. **Versioning**: Track changes to GHCID records over time

---

## Comprehensive Mapping Table

### HeritageCustodian Class Mappings

| Ontology | Class | Relationship | Notes |
|----------|-------|-------------|-------|
| **CIDOC-CRM** | `cidoc:E74_Group` | `owl:equivalentClass` | Primary mapping for museums |
| **RiC-O** | `rico:CorporateBody` | `owl:equivalentClass` | Primary mapping for archives |
| **Schema.org** | `schema:Museum` / `Library` / `ArchiveOrganization` | `rdf:type` (conditional) | Based on `institution_type` |
| **CPOV** | `cpov:PublicOrganisation` | `rdf:type` (conditional) | For public sector institutions |
| **W3C ORG** | `org:Organization` | `rdfs:subClassOf` | Generic superclass |
| **PROV-O** | `prov:Entity` | `rdf:type` | For provenance tracking |

### ChangeEvent Class Mappings

| Ontology | Class | Relationship | Notes |
|----------|-------|-------------|-------|
| **CIDOC-CRM** | `cidoc:E5_Event` | `rdfs:subClassOf` | General events |
| **RiC-O** | `rico:Activity` | `rdfs:subClassOf` | Archival events |
| **TOOI** | `tooi:Wijzigingsgebeurtenis` | `owl:equivalentClass` | Dutch government events |
| **PROV-O** | `prov:Activity` | `rdfs:subClassOf` | Provenance activities |

### Collection Class Mappings

| Ontology | Class | Relationship | Notes |
|----------|-------|-------------|-------|
| **CIDOC-CRM** | `cidoc:E78_Curated_Holding` | `rdfs:subClassOf` | Museum collections |
| **RiC-O** | `rico:RecordSet` | `owl:equivalentClass` | Archival record sets |
| **Schema.org** | `schema:ArchiveComponent` | `rdf:type` | Archival collections |

### Location Class Mappings

| Ontology | Class | Relationship | Notes |
|----------|-------|-------------|-------|
| **CIDOC-CRM** | `cidoc:E53_Place` | `rdfs:subClassOf` | Geographic places |
| **RiC-O** | `rico:Place` | `rdfs:subClassOf` | Archival places |
| **Schema.org** | `schema:Place` | `rdfs:subClassOf` | Generic places |
| **W3C ORG** | `org:Site` | `rdf:type` | Organizational sites |

### Identifier Class Mappings

| Ontology | Class | Relationship | Notes |
|----------|-------|-------------|-------|
| **CIDOC-CRM** | `cidoc:E42_Identifier` | `rdfs:subClassOf` | Generic identifiers |
| **RiC-O** | `rico:Identifier` | `rdfs:subClassOf` | Archival identifiers |

---

## RDF Serialization Examples

### Example 1: Dutch Archive with Multiple Ontologies

```turtle
@prefix ghcid:   <https://w3id.org/heritage/custodian/> .
@prefix cidoc:   <http://www.cidoc-crm.org/cidoc-crm/> .
@prefix rico:    <https://www.ica.org/standards/RiC/ontology#> .
@prefix schema:  <http://schema.org/> .
@prefix tooi: <https://identifier.overheid.nl/tooi/def/ont/> .
@prefix org:     <http://www.w3.org/ns/org#> .
@prefix prov:    <http://www.w3.org/ns/prov#> .
@prefix xsd:     <http://www.w3.org/2001/XMLSchema#> .

# Noord-Hollands Archief - Multi-ontology representation
ghcid:nl-haarnha
  # Type declarations
  a ghcid:HeritageCustodian,
    rico:CorporateBody,           # RiC-O: Archival institution
    schema:ArchiveOrganization,   # Schema.org: Web discoverability
    org:Organization,             # W3C ORG: Generic organization
    prov:Entity ;                 # PROV-O: Provenance entity
  
  # Basic metadata
  ghcid:name "Noord-Hollands Archief" ;
  schema:name "Noord-Hollands Archief" ;
  rico:hasOrHadName [
    a rico:Name ;
    rico:textualValue "Noord-Hollands Archief"@nl
  ] ;
  
  # Alternative names
  ghcid:alternative_names "NHA", "North Holland Archives" ;
  schema:alternateName "NHA"@en ;
  rico:hasOrHadOtherName [
    a rico:Name ;
    rico:textualValue "NHA"@en
  ] ;
  
  # Institution type
  ghcid:institution_type "ARCHIVE" ;
  rico:hasOrganizationType ghcid:ARCHIVE ;
  
  # Description
  ghcid:description "Provincial archive of North Holland, formed in 2001 through merger of Gemeentearchief Haarlem and Rijksarchief in Noord-Holland." ;
  schema:description "Provincial archive of North Holland, formed in 2001 through merger of Gemeentearchief Haarlem and Rijksarchief in Noord-Holland."@en ;
  rico:scopeAndContent "Provincial archive of North Holland, formed in 2001 through merger of Gemeentearchief Haarlem and Rijksarchief in Noord-Holland."@en ;
  
  # Location
  ghcid:location [
    a ghcid:Location, rico:Place, schema:Place ;
    ghcid:city "Haarlem" ;
    ghcid:country "NL" ;
    schema:addressLocality "Haarlem" ;
    schema:addressCountry "NL" ;
    rico:hasOrHadName [ rico:textualValue "Haarlem"@nl ]
  ] ;
  
  # Identifiers
  ghcid:identifier [
    a ghcid:Identifier, rico:Identifier ;
    ghcid:identifier_scheme "ISIL" ;
    ghcid:identifier_value "NL-HaarNHA" ;
    rico:identifierType "ISIL" ;
    rico:textualValue "NL-HaarNHA"
  ] ;
  
  schema:url "https://www.noord-hollandsarchief.nl" ;
  schema:sameAs <https://www.wikidata.org/wiki/Q2725652> ;
  
  # Change history (merger event)
  ghcid:change_history ghcid:event-nha-merger-2001 ;
  rico:agentIsTargetOfActivity ghcid:event-nha-merger-2001 ;
  
  # Predecessors (RiC-O)
  rico:hasPredecessor ghcid:nl-haarhaarlem, ghcid:nl-haarrijks ;
  
  # Collections
  schema:archiveHeld ghcid:collection-haarlem-city-records ;
  rico:hasOrHadCustody ghcid:collection-haarlem-city-records ;
  
  # Provenance
  prov:wasGeneratedBy ghcid:extraction-isil-registry-20251106 ;
  prov:hadPrimarySource <file:///data/ISIL-codes_2025-08-01.csv> ;
  prov:generatedAtTime "2025-11-06T10:30:00Z"^^xsd:dateTime .

# Merger event
ghcid:event-nha-merger-2001
  a ghcid:ChangeEvent,
    rico:Activity,              # RiC-O: Activity
    cidoc:E5_Event,             # CIDOC-CRM: Event
    tooi:Wijzigingsgebeurtenis, # TOOI: Dutch gov change event
    prov:Activity ;             # PROV-O: Activity
  
  ghcid:change_type "MERGER" ;
  ghcid:event_date "2001-01-01"^^xsd:date ;
  ghcid:event_description "Merger of Gemeentearchief Haarlem and Rijksarchief in Noord-Holland to form Noord-Hollands Archief." ;
  
  # RiC-O properties
  rico:hasActivityType ghcid:MERGER ;
  rico:hasBeginningDate "2001-01-01"^^xsd:date ;
  rico:agentAssociatedWithActivity ghcid:nl-haarhaarlem, ghcid:nl-haarrijks, ghcid:nl-haarnha ;
  
  # CIDOC-CRM properties
  cidoc:P4_has_time-span [
    a cidoc:E52_Time-Span ;
    cidoc:P82_at_some_time_within "2001-01-01"^^xsd:date
  ] ;
  cidoc:P14_carried_out_by ghcid:nl-haarnha ;
  
  # TOOI properties
  tooi:wijzigingsdatum "2001-01-01"^^xsd:date ;
  tooi:wijzigingstype ghcid:MERGER ;
  
  # PROV-O properties
  prov:generated ghcid:nl-haarnha ;
  prov:used ghcid:nl-haarhaarlem, ghcid:nl-haarrijks ;
  prov:atTime "2001-01-01T00:00:00Z"^^xsd:dateTime .
```

### Example 2: Museum with CIDOC-CRM Focus

```turtle
# Rijksmuseum - Museum-centric representation
ghcid:nl-amsnl-rms
  a ghcid:HeritageCustodian,
    cidoc:E74_Group,           # CIDOC-CRM: Museum as group
    schema:Museum,             # Schema.org: Museum type
    org:Organization ;
  
  ghcid:name "Rijksmuseum" ;
  cidoc:P1_is_identified_by [
    a cidoc:E41_Appellation ;
    cidoc:P190_has_symbolic_content "Rijksmuseum"
  ] ;
  
  ghcid:institution_type "MUSEUM" ;
  cidoc:P2_has_type ghcid:MUSEUM ;
  
  # Location (CIDOC-CRM E53_Place)
  cidoc:P74_has_current_or_former_residence [
    a cidoc:E53_Place ;
    cidoc:P87_is_identified_by [
      a cidoc:E44_Place_Appellation ;
      cidoc:P190_has_symbolic_content "Amsterdam, Netherlands"
    ]
  ] ;
  
  # Collections (CIDOC-CRM E78_Curated_Holding)
  cidoc:P109_has_current_or_former_curator ghcid:collection-rijksmuseum-dutch-masters ;
  
  schema:url "https://www.rijksmuseum.nl" ;
  schema:sameAs <https://www.wikidata.org/wiki/Q190804> .

# Collection
ghcid:collection-rijksmuseum-dutch-masters
  a ghcid:Collection,
    cidoc:E78_Curated_Holding ;
  
  ghcid:collection_name "Dutch Masters Collection" ;
  cidoc:P3_has_note "Collection of Dutch Golden Age paintings including works by Rembrandt, Vermeer, and Hals." ;
  
  cidoc:P109i_is_current_or_former_curator_of ghcid:nl-amsnl-rms .
```

### Example 3: JSON-LD for Schema.org

```json
{
  "@context": "https://schema.org",
  "@type": "ArchiveOrganization",
  "@id": "https://w3id.org/heritage/custodian/nl-haarnha",
  "name": "Noord-Hollands Archief",
  "alternateName": ["NHA", "North Holland Archives"],
  "description": "Provincial archive of North Holland, formed in 2001 through merger of Gemeentearchief Haarlem and Rijksarchief in Noord-Holland.",
  "url": "https://www.noord-hollandsarchief.nl",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q2725652",
    "https://viaf.org/viaf/..."
  ],
  "address": {
    "@type": "PostalAddress",
    "addressLocality": "Haarlem",
    "addressCountry": "NL"
  },
  "archiveHeld": {
    "@type": "ArchiveComponent",
    "@id": "https://w3id.org/heritage/custodian/collection-haarlem-city-records",
    "name": "Municipal Records of Haarlem",
    "temporalCoverage": "1245/2025",
    "description": "Historical records of the city of Haarlem spanning 780 years."
  },
  "foundingDate": "2001-01-01",
  "parentOrganization": null,
  "subOrganization": []
}
```

---

## Gap Analysis

### What GHCID Provides Beyond Standard Ontologies

1. **Persistent Identifiers (GHCID)**
   - **Unique**: Globally unique, persistent IDs for heritage institutions
   - **Versioned**: Change history tracking via GHCID history entries
   - **Resolvable**: Designed for HTTP resolution (future)
   - **Gap**: No standard ontology provides persistent IDs for organizations

2. **Change History Tracking**
   - **Comprehensive**: Dedicated ChangeEvent model with 11 event types
   - **Temporal**: Full history from founding to present
   - **Linked**: Events linked to affected organizations
   - **Gap**: Most ontologies don't track organizational evolution over time

3. **Multi-Tier Provenance**
   - **Data Quality**: 4-tier data quality system (TIER_1 through TIER_4)
   - **Confidence Scoring**: Numeric confidence scores for extracted data
   - **Source Tracking**: Precise provenance metadata
   - **Gap**: PROV-O lacks data quality tiers

4. **Institution Type Taxonomy**
   - **GLAM-Specific**: 13 institution types tailored for heritage sector
   - **Extensible**: Can add new types as needed
   - **Gap**: Schema.org has only 3 types (Museum, Library, ArchiveOrganization)

### What Standard Ontologies Provide That GHCID Could Use

1. **CIDOC-CRM Time-Spans**
   - **Feature**: E52_Time-Span for precise temporal modeling
   - **Benefit**: More granular than ISO 8601 dates (start/end, fuzzy dates)
   - **Recommendation**: Extend ChangeEvent to support CIDOC-CRM time-spans

2. **RiC-O Relationship Types**
   - **Feature**: 50+ relationship types (hierarchical, temporal, associative)
   - **Benefit**: Rich organizational relationship modeling
   - **Recommendation**: Add relationship modeling to GHCID schema (future)

3. **Schema.org Events**
   - **Feature**: schema:Event for public-facing event information
   - **Benefit**: Exhibition openings, closures, relocations for SEO
   - **Recommendation**: Link ChangeEvents to schema:Event for web discoverability

4. **CPOV Contact Points**
   - **Feature**: Structured contact information (already integrated!)
   - **Benefit**: Standardized contact metadata
   - **Status**: ✅ Already using `cpov:ContactPoint`

### Areas for Future Development

1. **Collection Metadata Enhancement**
   - Adopt CIDOC-CRM E78_Curated_Holding properties
   - Integrate RiC-O RecordSet relationships
   - Add Schema.org CreativeWork linkage

2. **Relationship Modeling**
   - Add parent/child organization relationships (org:subOrganizationOf)
   - Add partnership relationships (RiC-O rico:isAssociatedWith)
   - Add network membership (RiC-O rico:isMemberOf)

3. **Temporal Modeling**
   - Support fuzzy dates ("circa 1850", "early 20th century")
   - Use CIDOC-CRM E52_Time-Span for date ranges
   - Add temporal qualifiers (RiC-O rico:certainty)

4. **Rights and Licensing**
   - Add Dublin Core Terms rights metadata
   - Integrate Creative Commons licenses
   - Support ODRL for data usage rights

---

## Implementation Recommendations

### 1. RDF Export Priority

When exporting GHCID data to RDF, include:

**REQUIRED** (all institutions):
- W3C ORG: `org:Organization` (generic compatibility)
- PROV-O: `prov:Entity` (provenance)
- Schema.org: Institution-type-specific class (SEO)

**RECOMMENDED** (based on institution type):
- Archives → RiC-O: `rico:CorporateBody` (archival standard)
- Museums → CIDOC-CRM: `cidoc:E74_Group` (museum standard)
- Dutch institutions → TOOI: `tooi:Organisatie` (Dutch gov)
- EU institutions → CPOV: `cpov:PublicOrganisation` (EU public sector)

### 2. JSON-LD Context Design

Create a comprehensive JSON-LD context file:

```json
{
  "@context": {
    "ghcid": "https://w3id.org/heritage/custodian/",
    "cidoc": "http://www.cidoc-crm.org/cidoc-crm/",
    "rico": "https://www.ica.org/standards/RiC/ontology#",
    "schema": "https://schema.org/",
    "org": "http://www.w3.org/ns/org#",
    "prov": "http://www.w3.org/ns/prov#",
    "cpov": "http://data.europa.eu/m8g/",
    "tooiont": "https://identifier.overheid.nl/tooi/def/ont/",
    
    "HeritageCustodian": {
      "@id": "ghcid:HeritageCustodian",
      "@type": "@id"
    },
    "name": {
      "@id": "schema:name",
      "@container": "@language"
    },
    "institution_type": {
      "@id": "ghcid:institution_type",
      "@type": "@vocab"
    },
    ...
  }
}
```

### 3. Validation Strategy

Validate RDF exports against ontology specifications:

1. **Schema.org**: Use Google's Structured Data Testing Tool
2. **CIDOC-CRM**: Validate with CIDOC-CRM RDFS/OWL definitions
3. **RiC-O**: Validate with RiC-O v1.1 SHACL shapes (if available)
4. **W3C Standards**: Use W3C RDF validator

### 4. Incremental Adoption

**Phase 1** (Current): Basic ontology alignment
- Export as W3C ORG + Schema.org
- Include PROV-O provenance
- Minimal RDF serialization

**Phase 2** (Next 6 months): Domain-specific ontologies
- Add RiC-O for archives
- Add CIDOC-CRM for museums
- Add TOOI for Dutch institutions

**Phase 3** (Future): Advanced features
- Full relationship modeling
- CIDOC-CRM time-spans
- Rights and licensing metadata

### 5. Documentation and Examples

Provide clear examples for data consumers:

- **GitHub repo**: `/examples/rdf/` directory with Turtle, JSON-LD, RDF/XML
- **API documentation**: Ontology alignment tables in API docs
- **SPARQL queries**: Example queries for each ontology
- **Conversion scripts**: LinkML → RDF conversion utilities

---

## Conclusion

The GHCID schema achieves **interoperability** with seven major ontologies while maintaining unique capabilities for persistent identification and change tracking. By aligning with international standards (CIDOC-CRM, RiC-O, Schema.org) and regional standards (CPOV, TOOI), GHCID enables seamless data exchange across the global heritage sector.

**Key Takeaways**:

1. **RiC-O is critical** for archival institutions (highest priority)
2. **Schema.org enables web discoverability** (required for SEO)
3. **CIDOC-CRM supports museum integration** (recommended for museums)
4. **Multiple ontologies can coexist** (use conditional type assignments)
5. **GHCID adds unique value** (persistent IDs, change history, data quality tiers)

**Next Steps**:

1. ✅ Complete ONTOLOGY_INTEGRATION.md (this document)
2. ⏳ Create GHCID_PID_SCHEME.md (persistent identifier specification)
3. ⏳ Implement RDF export utilities in Python
4. ⏳ Generate JSON-LD context file
5. ⏳ Create example RDF serializations for each ontology

---

**Revision History**:
- v1.0 (2025-11-06): Initial comprehensive ontology integration guide

**Maintained By**: GLAM Data Extraction Project  
**Contact**: [Project repository](https://github.com/kempersc/glam)