# DBpedia Ontology Integration for Heritage Custodian Project

**Date**: 2025-11-20  
**Purpose**: Document DBpedia Ontology (DBO) conventions for mapping Wikidata entities to specialized heritage ontologies

---

## Executive Summary

**DBpedia Ontology (DBO)** provides a critical bridge between Wikidata entities and formal ontology classes. This document establishes conventions for integrating DBO mappings into the heritage custodian ontology enrichment workflow.

**Key Finding**: DBpedia already maps many Wikidata GLAM entities to ontology classes via `owl:equivalentClass` assertions. We should leverage these existing mappings instead of creating them from scratch.

---

## DBpedia Ontology Overview

**Namespace**: `http://dbpedia.org/ontology/`  
**Prefix**: `dbo:`  
**Coverage**: 768 classes, 3000 properties, ~4.2M instances  
**Scope**: Cross-domain ontology (shallow but broad coverage)

### Key Resources

- **Ontology Browser**: http://dbpedia.org/ontology/
- **SPARQL Endpoint**: http://dbpedia.org/sparql
- **Mappings Wiki**: http://mappings.dbpedia.org
- **Archivo (Ontology Archive)**: https://archivo.dbpedia.org/info?o=http://dbpedia.org/ontology/
- **Development Version**: https://databus.dbpedia.org/ontologies/dbpedia.org/ontology--DEV

---

## Why DBpedia Matters for This Project

### 1. **Pre-existing Wikidata Mappings**

DBpedia already maps many heritage institution Wikidata entities to ontology classes:

```turtle
dbo:Museum owl:equivalentClass wd:Q33506 .
dbo:Library owl:equivalentClass wd:Q7075 .
dbo:Archive owl:equivalentClass wd:Q166118 .
```

**Benefit**: We can use DBpedia as an intermediary to discover ontology mappings for Wikidata entities.

### 2. **Schema.org Alignment**

DBpedia classes map to Schema.org (which we already use):

```turtle
dbo:Library owl:equivalentClass schema:Library .
```

**Benefit**: DBpedia validates our existing Schema.org mappings.

### 3. **Domain-Specific Properties**

DBpedia defines heritage-specific properties:

- `dbo:collection` - Museum collections
- `dbo:curator` - Museum curator
- `dbo:museumType` - Museum specialization
- `dbo:isil` - ISIL code (for libraries)
- `dbo:numberOfCollectionItems` - Collection size

**Benefit**: We can reference DBpedia properties in our mappings instead of inventing custom ones.

---

## DBpedia Heritage Classes

### Museums

**Class**: `dbo:Museum`  
**Wikidata**: `wd:Q33506`  
**Subclass of**: `dbo:Building`  
**Properties**:
- `dbo:collection` (museum collections)
- `dbo:curator` (curator name)
- `dbo:museumType` (specialization: art, history, science, etc.)

**Example RDF**:
```turtle
<http://dbpedia.org/resource/Rijksmuseum>
  rdf:type dbo:Museum ;
  dbo:collection "Dutch Golden Age paintings" ;
  dbo:curator "Taco Dibbits" ;
  dbo:museumType "Art museum" .
```

### Libraries

**Class**: `dbo:Library`  
**Wikidata**: `wd:Q7075`  
**Schema.org**: `schema:Library`  
**Subclass of**: `dbo:EducationalInstitution`  
**Properties**:
- `dbo:isil` (ISIL code)
- `dbo:numberOfCollectionItems` (collection size)

**Example RDF**:
```turtle
<http://dbpedia.org/resource/Library_of_Congress>
  rdf:type dbo:Library ;
  dbo:isil "US-DLC" ;
  dbo:numberOfCollectionItems 17000000 .
```

### Archives

**Class**: `dbo:Archive`  
**Wikidata**: `wd:Q166118`  
**Subclass of**: `dbo:CollectionOfValuables`  
**Properties**: (fewer specialized properties than Museum/Library)

**Example RDF**:
```turtle
<http://dbpedia.org/resource/National_Archives_and_Records_Administration>
  rdf:type dbo:Archive ;
  rdfs:label "National Archives and Records Administration"@en .
```

---

## Integration Workflow for Ontology Enrichment

### Step 1: Check DBpedia for Wikidata Mapping

When enriching a Wikidata entity (e.g., Q2772772 - military museum):

```sparql
# Query DBpedia SPARQL endpoint
SELECT ?dboClass WHERE {
  ?dboClass owl:equivalentClass <http://www.wikidata.org/entity/Q2772772> .
}
```

**If match found**: Use DBpedia class as secondary/tertiary ontology reference.

### Step 2: Discover DBpedia Subclass Hierarchy

```sparql
# Find superclasses
SELECT ?superclass WHERE {
  dbo:Museum rdfs:subClassOf ?superclass .
}
# Result: dbo:Building
```

**Use this to understand** where DBpedia places the entity in the ontology hierarchy.

### Step 3: Extract DBpedia Properties

```sparql
# Find properties applicable to Museum class
SELECT DISTINCT ?property WHERE {
  ?property rdfs:domain dbo:Museum .
}
```

**Result**:
- `dbo:collection`
- `dbo:curator`
- `dbo:museumType`

**Action**: Reference these properties in our ontology mapping `properties:` section.

### Step 4: Document DBpedia Mapping in YAML

```yaml
ontology_mapping:
  wikidata_source: Q2772772
  dbpedia_class: dbo:Museum  # ← ADD THIS
  dbpedia_equivalent_wikidata: wd:Q33506  # ← ADD THIS
  
  custodian_ontology:
    public_sector:
      class: cpov:PublicOrganisation
      secondary_class: schema:Museum
      tertiary_class: dbo:Museum  # ← REFERENCE DBpedia
      quaternary_class: crm:E39_Actor
      
    properties:
    - label: dbo:collection  # ← USE DBpedia property
      value:
      - label: Museum collections
    - label: dbo:curator  # ← USE DBpedia property
      value:
      - label: Curator name
    - label: dbo:museumType  # ← USE DBpedia property
      value:
      - label: Museum specialization (military, art, history, etc.)
```

---

## DBpedia Advantages Over Wikidata

| Feature | Wikidata | DBpedia |
|---------|----------|---------|
| **Ontology Structure** | Flat entity graph | Hierarchical class ontology |
| **Property Definitions** | No formal domains/ranges | Typed properties with domain/range |
| **OWL Semantics** | Limited OWL support | Full OWL ontology |
| **Reasoning Support** | Manual queries | OWL reasoning possible |
| **Multilingual Labels** | Excellent | Good (40+ languages) |
| **Heritage Coverage** | Comprehensive instances | Structured classes + properties |

**Use Case**: Wikidata provides entity instances; DBpedia provides ontology structure.

---

## Updated Ontology Mapping Template

### New Fields to Add

```yaml
ontology_mapping:
  wikidata_source: Q[number]
  
  # NEW: DBpedia integration
  dbpedia_mapping:
    dbpedia_class: dbo:[ClassName]  # If DBpedia has equivalent class
    dbpedia_equivalent_wikidata: wd:Q[number]  # Wikidata entity DBpedia maps to
    dbpedia_properties:  # DBpedia-specific properties to use
    - dbo:collection
    - dbo:curator
    - dbo:isil
    sparql_query: |  # SPARQL query used to discover mapping
      SELECT ?dboClass WHERE {
        ?dboClass owl:equivalentClass <http://www.wikidata.org/entity/Q[number]> .
      }
  
  semantic_aspects: [...]
  complexity_score: N
  
  custodian_ontology:
    public_sector:
      class: cpov:PublicOrganisation
      secondary_class: schema:Museum
      tertiary_class: dbo:Museum  # ← REFERENCE DBpedia class
      quaternary_class: crm:E39_Actor
      
      properties:
      - label: dbo:collection  # ← USE DBpedia properties
        value:
        - label: Collection description
```

---

## DBpedia Properties for Heritage Institutions

### Museum Properties

| Property | Domain | Range | Description |
|----------|--------|-------|-------------|
| `dbo:collection` | `dbo:Museum` | `xsd:string` | Collections held by museum |
| `dbo:curator` | `dbo:Museum` | `dbo:Person` | Museum curator |
| `dbo:museumType` | `dbo:Museum` | `xsd:string` | Museum specialization |

### Library Properties

| Property | Domain | Range | Description |
|----------|--------|-------|-------------|
| `dbo:isil` | `dbo:Library` | `xsd:string` | ISIL code |
| `dbo:numberOfCollectionItems` | `dbo:Library` | `xsd:integer` | Collection size |

### General Organizational Properties

| Property | Domain | Range | Description |
|----------|--------|-------|-------------|
| `dbo:foundingDate` | `dbo:Organisation` | `xsd:date` | Founding date |
| `dbo:dissolutionDate` | `dbo:Organisation` | `xsd:date` | Closure date |
| `dbo:location` | `dbo:Organisation` | `dbo:Place` | Physical location |
| `dbo:affiliation` | `dbo:Organisation` | `dbo:Organisation` | Parent organization |

---

## Comparison: CPOV vs Schema.org vs DBpedia

### Museum Example

```turtle
# CPOV (EU Public Sector)
<http://example.org/rijksmuseum>
  rdf:type cpov:PublicOrganisation ;
  skos:prefLabel "Rijksmuseum" ;
  dct:identifier "NL-AmRMA" .  # ISIL

# Schema.org (Web Semantics)
<http://example.org/rijksmuseum>
  rdf:type schema:Museum ;
  schema:name "Rijksmuseum" ;
  schema:identifier "NL-AmRMA" .

# DBpedia (Cross-Domain Ontology)
<http://example.org/rijksmuseum>
  rdf:type dbo:Museum ;
  rdfs:label "Rijksmuseum" ;
  dbo:isil "NL-AmRMA" ;
  dbo:collection "Dutch Golden Age paintings" ;
  dbo:curator "Taco Dibbits" .
```

**Decision**: Use ALL THREE in multi-typed assertions for maximum interoperability.

---

## SPARQL Queries for DBpedia Integration

### Query 1: Find DBpedia Class for Wikidata Entity

```sparql
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX wd: <http://www.wikidata.org/entity/>

SELECT ?dboClass ?label WHERE {
  ?dboClass owl:equivalentClass wd:Q2772772 .
  ?dboClass rdfs:label ?label .
  FILTER(LANG(?label) = "en")
}
```

### Query 2: Find All Museum-Related DBpedia Classes

```sparql
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?class ?label WHERE {
  ?class rdfs:subClassOf* dbo:Museum .
  ?class rdfs:label ?label .
  FILTER(LANG(?label) = "en")
}
```

### Query 3: Find DBpedia Properties for a Class

```sparql
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?property ?label WHERE {
  ?property rdfs:domain dbo:Museum .
  ?property rdfs:label ?label .
  FILTER(LANG(?label) = "en")
}
```

---

## Implementation Recommendations

### Recommendation 1: Add DBpedia as Fourth Ontology Layer

**Current**: CPOV (primary) + Schema.org (secondary) + CIDOC-CRM (tertiary)  
**Proposed**: CPOV + Schema.org + **DBpedia** + CIDOC-CRM

**Rationale**: DBpedia bridges Wikidata entities to formal ontologies.

### Recommendation 2: Use DBpedia Properties in LinkML Schema

**Current**: Custom properties or Schema.org properties  
**Proposed**: Reference DBpedia properties when available

**Example** (LinkML schema):
```yaml
HeritageCustodian:
  slots:
    collection_description:
      slot_uri: dbo:collection  # ← Map to DBpedia property
    curator_name:
      slot_uri: dbo:curator
    museum_type:
      slot_uri: dbo:museumType
    isil_code:
      slot_uri: dbo:isil
```

### Recommendation 3: Create DBpedia Mapping Cache

**Problem**: Querying DBpedia SPARQL endpoint for every entity is slow.  
**Solution**: Pre-cache Wikidata → DBpedia mappings for common heritage classes.

**Script** (`scripts/cache_dbpedia_mappings.py`):
```python
import requests

DBPEDIA_SPARQL = "http://dbpedia.org/sparql"

def get_dbpedia_class(wikidata_id):
    """Query DBpedia for equivalent class of Wikidata entity."""
    query = f"""
    PREFIX owl: <http://www.w3.org/2002/07/owl#>
    PREFIX wd: <http://www.wikidata.org/entity/>
    
    SELECT ?dboClass WHERE {{
      ?dboClass owl:equivalentClass wd:{wikidata_id} .
    }}
    """
    response = requests.get(DBPEDIA_SPARQL, params={
        'query': query,
        'format': 'json'
    })
    results = response.json()['results']['bindings']
    if results:
        return results[0]['dboClass']['value']
    return None

# Cache mappings for GLAM entities
cache = {}
for qid in ['Q33506', 'Q7075', 'Q166118', 'Q2772772', ...]:
    cache[qid] = get_dbpedia_class(qid)

# Save to YAML
with open('data/ontology/dbpedia_wikidata_mappings.yaml', 'w') as f:
    yaml.dump(cache, f)
```

### Recommendation 4: Enrich Ontology Mapping Workflow

**Updated workflow** (`.opencode/agent/ontology-mapping-rules.md`):

1. Read Wikidata entity metadata
2. **Query DBpedia for equivalent class** ← NEW STEP
3. Search base ontologies (CPOV, TOOI, Schema.org, CIDOC-CRM)
4. **Reference DBpedia properties** ← NEW STEP
5. Map to ontology classes
6. Document rationale
7. Write ontology_mapping YAML

---

## Example: Military Museum with DBpedia Integration

```yaml
- label: Q2772772
  hypernym:
  - museum
  type:
  - M
  ontology_mapping:
    wikidata_source: Q2772772
    
    # DBpedia integration
    dbpedia_mapping:
      dbpedia_class: dbo:Museum
      dbpedia_equivalent_wikidata: wd:Q33506
      dbpedia_subclass_of: dbo:Building
      dbpedia_properties:
      - dbo:collection
      - dbo:curator
      - dbo:museumType
      sparql_discovery_date: "2025-11-20"
    
    semantic_aspects:
    - custodian
    - collections
    
    complexity_score: 4
    
    custodian_ontology:
      public_sector:
        class: cpov:PublicOrganisation
        namespace: http://data.europa.eu/m8g/
        secondary_class: schema:Museum
        tertiary_class: dbo:Museum  # ← DBpedia class
        quaternary_class: crm:E39_Actor
        
        properties:
        - label: dbo:collection
          value:
          - label: Military artifacts and archival records
        - label: dbo:curator
          value:
          - label: Museum curator name
        - label: dbo:museumType
          value:
          - label: Military history specialization
        - label: dct:identifier
          value:
          - label: ISIL code
        - label: schema:url
          value:
          - label: Official website
    
    collections_ontology:
      museum_collections:
        class: crm:E78_Curated_Holding
        properties:
        - label: dbo:collection  # ← Reference DBpedia property
          value:
          - label: Military artifacts description
```

---

## References

- **DBpedia Homepage**: https://www.dbpedia.org/
- **DBpedia Ontology**: http://dbpedia.org/ontology/
- **DBpedia SPARQL Endpoint**: http://dbpedia.org/sparql
- **DBpedia Mappings Wiki**: http://mappings.dbpedia.org
- **Archivo (DBpedia Ontology Archive)**: https://archivo.dbpedia.org/
- **DBpedia Databus**: https://databus.dbpedia.org/ontologies/dbpedia.org/ontology--DEV

---

## Next Steps

1. ✅ Document DBpedia integration conventions (THIS DOCUMENT)
2. ⏳ Create DBpedia → Wikidata mapping cache script
3. ⏳ Update `.opencode/agent/ontology-mapping-rules.md` with DBpedia step
4. ⏳ Retrofit existing ontology mappings (Q1802963, Q3694, Q2927789) with DBpedia references
5. ⏳ Add `dbpedia_class` field to LinkML schema
6. ⏳ Continue ontology enrichment with DBpedia integration

---

**Version**: 1.0  
**Last Updated**: 2025-11-20  
**Maintained By**: Heritage Custodian Ontology Project