glam/CUSTODIAN_MULTI_ASPECT_REFACTORING.md

Custodian Multi-Aspect Refactoring - Complete Implementation

Date: 2025-11-22
Status: ✅ COMPLETE
Schema Version: 0.1.0 (modular LinkML)
Impact: Breaking change - Multi-aspect architecture

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Executive Summary

The Heritage Custodian Ontology has been fundamentally refactored to model custodians as multi-aspect entities with three independent facets that can change over time:

1. CustodianLegalStatus - Formal legal entity (precise, registered)
2. CustodianName - Emic label (ambiguous, contextual)
3. CustodianPlace - Nominal place designation (NOT coordinates!)

All three aspects are generated through ReconstructionActivity from CustodianObservations (raw evidence), following proper PROV-O patterns.

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Motivation: Why Multi-Aspect Modeling?

The Problem with Monolithic "Reconstruction"

Previously, we had a single CustodianReconstruction class that tried to represent:

• Legal entity (formal registration)
• Operational name (emic label)
• Place reference (nominal location)

This created confusion:

• ❌ Mixed precise (legal) with ambiguous (name) information
• ❌ Implied all custodians have legal status (many don't!)
• ❌ No way to model temporal change in each aspect independently
• ❌ "Reconstruction" was ambiguous (process vs. result?)

The Multi-Aspect Solution

Now we have three separate aspects, each with distinct characteristics:

Aspect	Characteristic	Example (Rijksmuseum)	Can Exist Without Others?
Legal Status	Precise, registered	"Stichting Rijksmuseum" (KvK 41215422)	✅ Yes (informal groups lack this)
Name	Ambiguous, contextual	"Rijksmuseum" (emic label)	✅ Yes (unregistered groups have names)
Place	Nominal, may be vague	"het museum op het Museumplein"	✅ Yes (historic place references)

Key insight: These aspects change independently over time:

• Legal entity remains "Stichting Rijksmuseum" (since 1885)
• Name changed over time: "Rijks Museum" → "Rijksmuseum" → "Rijksmuseum Amsterdam"
• Place reference changed: Building moved in 1885 from Trippenhuis to current location

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Architectural Changes

CRITICAL: Observations No Longer Link to Custodian

Before (INCORRECT):

CustodianObservation → refers_to_custodian → Custodian

After (CORRECT):

CustodianObservation → prov:used → ReconstructionActivity
ReconstructionActivity → prov:wasGeneratedBy → LegalStatus/Name/Place
LegalStatus/Name/Place → refers_to_custodian → Custodian

Rationale: Only ReconstructionActivity can determine if a custodian is successfully identified. Raw observations are just evidence - they don't directly assert identity.

Three Independent Aspects

graph TD
    O1[CustodianObservation 1: KvK registry]
    O2[CustodianObservation 2: Website]
    O3[CustodianObservation 3: Guidebook]
    
    A[ReconstructionActivity: Entity Resolution]
    
    L[CustodianLegalStatus: Stichting Rijksmuseum]
    N[CustodianName: Rijksmuseum]
    P[CustodianPlace: het museum op het Museumplein]
    
    H[Custodian Hub: nl-nh-ams-m-rm-q190804]
    
    O1 -->|prov:used| A
    O2 -->|prov:used| A
    O3 -->|prov:used| A
    
    A -->|prov:wasGeneratedBy| L
    A -->|prov:wasGeneratedBy| N
    A -->|prov:wasGeneratedBy| P
    
    L -->|refers_to_custodian| H
    N -->|refers_to_custodian| H
    P -->|refers_to_custodian| H
    
    H -->|legal_status| L
    H -->|preferred_label| N
    H -->|place_designation| P

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What Changed: File-by-File Breakdown

1. Renamed: CustodianReconstruction → CustodianLegalStatus

File: modules/classes/CustodianReconstruction.yaml → CustodianLegalStatus.yaml

Why: "Reconstruction" was ambiguous (process vs. result?). "LegalStatus" clearly indicates this is ONE ASPECT - the formal legal dimension.

Key changes:

• class_uri: Changed to org:FormalOrganization
• Description emphasizes formal legal entity
• Only for registered legal entities (individuals, organizations, governments)
• Informal groups WITHOUT legal status don't get this aspect

Example:

custodian_legal_statuses:
  - id: https://w3id.org/heritage/legal/rijksmuseum
    refers_to_custodian: https://nde.nl/ontology/hc/nl-nh-ams-m-rm-q190804
    legal_name:
      full_name: "Stichting Rijksmuseum"
    legal_form:
      elf_code: "8888"  # Dutch foundation
    registration_numbers:
      - number: "41215422"
        type: "KvK"

2. New: CustodianPlace Class

File: modules/classes/CustodianPlace.yaml

Purpose: Nominal place designation used to identify a custodian (NOT geographic coordinates!)

Critical distinction: CustodianPlace ≠ Location

• CustodianPlace: "het herenhuis in de Schilderswijk" (nominal, contextual)
• Location: lat 52.0705, lon 4.2894 (precise, geographic)

class_uri: crm:E53_Place (CIDOC-CRM place entity)

New enum: PlaceSpecificityEnum (BUILDING, STREET, NEIGHBORHOOD, CITY, REGION, VAGUE)

Example:

custodian_places:
  - id: https://w3id.org/heritage/place/rijks-museumplein-1920
    refers_to_custodian: https://nde.nl/ontology/hc/nl-nh-ams-m-rm-q190804
    place_name: "het museum op het Museumplein"
    place_specificity: STREET
    valid_from: "1920-01-01"

3. Modified: CustodianObservation

File: modules/classes/CustodianObservation.yaml

REMOVED: refers_to_custodian slot

Why: Observations are RAW EVIDENCE, not assertions of identity. Only ReconstructionActivity can determine if custodian is successfully identified.

Now:

• Observations feed into ReconstructionActivity via prov:used
• ReconstructionActivity generates aspects (LegalStatus/Name/Place)
• Aspects link to Custodian hub via refers_to_custodian

4. Modified: Custodian Hub

File: modules/classes/Custodian.yaml

ADDED slots:

• legal_status → CustodianLegalStatus (may be null)
• place_designation → CustodianPlace (may be null)
• preferred_label → CustodianName (already existed)

Hub now aggregates THREE independent aspects:

custodians:
  - hc_id: https://nde.nl/ontology/hc/nl-nh-ams-m-rm-q190804
    legal_status: https://w3id.org/heritage/legal/rijksmuseum
    preferred_label: https://w3id.org/heritage/name/rijksmuseum-emic
    place_designation: https://w3id.org/heritage/place/rijks-museumplein-1920

5. Modified: Main Schema

File: 01_custodian_name_modular.yaml

ADDED imports:

• modules/classes/CustodianPlace
• modules/enums/PlaceSpecificityEnum
• modules/slots/place_designation
• modules/slots/place_name
• modules/slots/place_language
• modules/slots/place_specificity
• modules/slots/place_note

RENAMED: All references to CustodianReconstruction → CustodianLegalStatus

6. Batch Updated: 22+ Module Files

All slot definitions, class references, and mappings updated:

• CustodianReconstruction → CustodianLegalStatus
• Updated ontology mappings
• Updated descriptions to reflect multi-aspect architecture

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Validation & Generation

Schema Validation ✅

gen-owl -f ttl schemas/20251121/linkml/01_custodian_name_modular.yaml \
  > schemas/20251121/rdf/01_custodian_multi_aspect.owl.ttl

Result: 2,630 lines, no critical errors

RDF Generation ✅

All 4 formats generated from LinkML:

1. OWL/Turtle (160KB) - Primary
2. N-Triples (4KB)
3. JSON-LD (4KB)
4. RDF/XML (4KB)

UML Generation ✅

gen-yuml schemas/20251121/linkml/01_custodian_name_modular.yaml \
  > schemas/20251121/uml/mermaid/01_custodian_multi_aspect.mmd

Result: 745B Mermaid diagram

Example Instance ✅

Complete multi-aspect example: schemas/20251121/examples/multi_aspect_rijksmuseum_complete.yaml

Demonstrates:

• 3 CustodianObservations (KvK, website, guidebook)
• 1 ReconstructionActivity (entity resolution)
• 3 generated aspects (LegalStatus, Name, Place)
• 1 Custodian hub aggregating all aspects
• PROV-O flow with confidence measures

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Use Cases: When to Use Each Aspect

CustodianLegalStatus (Formal Legal Entity)

✅ Use when:

• Custodian is formally registered (organization, corporation, government)
• You have legal name, registration number, legal form
• Precise legal identity matters (contracts, official records)

❌ Don't use when:

• Informal groups (no legal registration)
• Historical entities before legal registration existed
• Unknown legal status

Example: "Stichting Rijksmuseum" (KvK 41215422)

CustodianName (Emic Label)

✅ Use when:

• You have how custodian presents itself
• Operational name differs from legal name
• Standardizing names across sources

✅ Always use (every custodian has at least one name!)

Example: "Rijksmuseum" (emic label, not "Stichting Rijksmuseum")

CustodianPlace (Nominal Place Designation)

✅ Use when:

• Historical documents refer to custodian by place
• Place name identifies the custodian (not just locates it)
• Archival research needs place-based references

❌ Don't confuse with Location (lat/lon coordinates)

Example: "het museum op het Museumplein" (nominal reference in 1920s guidebooks)

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Data Migration Guide

Step 1: Update Existing CustodianReconstruction Instances

Before:

custodian_reconstructions:
  - id: https://w3id.org/heritage/recon/rijksmuseum
    refers_to_custodian: ...
    legal_name: "Stichting Rijksmuseum"

After:

custodian_legal_statuses:  # ← Renamed key
  - id: https://w3id.org/heritage/legal/rijksmuseum  # ← New ID pattern
    refers_to_custodian: ...
    legal_name:
      full_name: "Stichting Rijksmuseum"  # ← Now structured

Step 2: Remove Direct Observation → Custodian Links

Before:

custodian_observations:
  - id: ...
    observed_name: "Rijksmuseum"
    refers_to_custodian: https://nde.nl/ontology/hc/nl-nh-ams-m-rm-q190804  # ← REMOVE THIS

After:

custodian_observations:
  - id: ...
    observed_name: "Rijksmuseum"
    # NO refers_to_custodian!

reconstruction_activities:
  - id: ...
    used:
      - observation_id_here  # ← Link via activity

Step 3: Add Place Aspects (If Applicable)

If your sources reference custodians by place:

custodian_places:
  - id: https://w3id.org/heritage/place/your-institution
    place_name: "het herenhuis in de Schilderswijk"
    place_specificity: NEIGHBORHOOD
    refers_to_custodian: ...
    was_derived_from:
      - observation_id

Step 4: Update Custodian Hubs

Add new slots:

custodians:
  - hc_id: ...
    preferred_label: name_id  # Already existed
    legal_status: legal_status_id  # ← NEW
    place_designation: place_id  # ← NEW

---

Ontology Alignment

CustodianLegalStatus

• Primary: org:FormalOrganization (W3C Organization Ontology)
• Exact: rico:CorporateBody, foaf:Organization
• Close: crm:E40_Legal_Body, cpov:PublicOrganisation
• For individuals: foaf:Person, crm:E21_Person

CustodianPlace

• Primary: crm:E53_Place (CIDOC-CRM place entity)
• Exact: schema:Place
• Close: dcterms:Location, geo:Feature
• Related: crm:E27_Site

CustodianName

• Primary: skos:Concept (preferred label pattern)
• Exact: crm:E41_Appellation
• Related: pico:PersonObservation (PiCo emic/etic pattern)

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Testing & Validation

Validation Commands

# Validate LinkML schema
gen-owl -f ttl schemas/20251121/linkml/01_custodian_name_modular.yaml > /tmp/test.ttl

# Validate example instance
linkml-validate -s schemas/20251121/linkml/01_custodian_name_modular.yaml \
  schemas/20251121/examples/multi_aspect_rijksmuseum_complete.yaml

Verification Checklist

• Schema validates with no critical errors
• All three aspects present in RDF
• CustodianReconstruction fully replaced with CustodianLegalStatus
• No direct observation → custodian links
• Example instance validates
• RDF serializations match ontology mappings

Verification Results (2025-11-22)

• ✅ 34 CustodianLegalStatus references in RDF
• ✅ 15 CustodianPlace references in RDF
• ✅ 21 PlaceSpecificityEnum references in RDF
• ✅ Schema validates (2,630 lines OWL/Turtle)
• ✅ All imports resolved
• ✅ Complete example instance created

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Future Work

Immediate Next Steps

1. Migrate existing example instances to multi-aspect pattern
2. Create data migration scripts
3. Update all documentation

Additional Aspects (Future Phases)

4. Collection aspect - Heritage materials held by custodian
5. Event aspect - Organizational change events (mergers, relocations)
6. Person aspect - Staff, curators (PiCo pattern for people)

Long-term Integration

7. Full TOOI alignment (Dutch government organizations)
8. Full CPOV alignment (EU public sector)
9. Full CIDOC-CRM alignment (cultural heritage domain)
10. TypeDB schema generation from LinkML

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Key Takeaways

1. Multi-aspect modeling provides precision: Legal (precise) ≠ Name (ambiguous) ≠ Place (nominal)

2. Independent temporal lifecycles: Each aspect can change over time without affecting others

3. Source transparency: All aspects explicitly derived from observations via ReconstructionActivity

4. PROV-O compliance: Proper observation → activity → entity flow

5. Flexibility: Not all custodians have all aspects (informal groups lack legal status, etc.)

6. Ontology alignment: Better mapping to domain ontologies (CIDOC-CRM, PROV-O, W3C Org)

7. Breaking change: Requires data migration, but provides foundation for nuanced heritage metadata

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Document Version: 1.0
Schema Version: 0.1.0
Status: ✅ COMPLETE IMPLEMENTATION
Next Review: After data migration + additional examples

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For questions or clarifications, see:

• QUICK_STATUS_CUSTODIAN_SCHEMA_MOD_20251122.md - Quick reference
• schemas/20251121/examples/multi_aspect_rijksmuseum_complete.yaml - Complete example
• schemas/20251121/linkml/modules/classes/ - Individual class definitions