# Critical Architectural Fix - Observation-Reconstruction Relationships

**Date**: 2025-11-22  
**Status**: 🚨 CRITICAL FIX NEEDED  
**Priority**: HIGH

## Problem Identified

The current schema has **incorrect relationships** between key classes:

### Current Issues

1. **ConfidenceMeasure attached to wrong class**
   - ❌ Current: `CustodianReconstruction.confidence_score` → `ConfidenceMeasure`
   - ✅ Correct: `ReconstructionActivity.confidence_score` → `ConfidenceMeasure`
   - **Rationale**: Confidence measures the PROCESS quality, not the RESULT

2. **CustodianObservation not linked to ReconstructionActivity**
   - ❌ Current: No direct link from `CustodianObservation` → `ReconstructionActivity`
   - ✅ Correct: `ReconstructionActivity.used` → `CustodianObservation` (multivalued)
   - **Rationale**: PROV-O Activity uses Entities as inputs

3. **CustodianName incorrectly subclasses CustodianObservation**
   - ❌ Current: `CustodianName is_a CustodianObservation`
   - ✅ Correct: `CustodianName` is **DERIVED FROM** `CustodianObservation` (not inheritance!)
   - **Rationale**: CustodianName is the OUTPUT of interpretation, not a type of observation

4. **CustodianName not directly linked to Custodian hub**
   - ❌ Current: No direct link from `Custodian` → `CustodianName`
   - ✅ Correct: `Custodian.preferred_label` → `CustodianName`
   - **Rationale**: The hub needs a direct reference to its standardized emic name

---

## Correct Architecture Pattern

### PROV-O Activity Pattern

```
CustodianObservation (Entity - Input)
    ↓ prov:used
ReconstructionActivity (Activity - Process)
    ├── confidence_score → ConfidenceMeasure (quality of process)
    ├── prov:wasGeneratedBy → Agent
    ↓ prov:wasGeneratedBy (output)
CustodianReconstruction OR CustodianName (Entity - Output)
```

### Key Principles

1. **Activity Uses Entities** (`prov:used`)
   - ReconstructionActivity consumes CustodianObservation(s)
   - Multiple observations can feed into one activity

2. **Activity Generates Entities** (`prov:wasGeneratedBy`)
   - ReconstructionActivity generates CustodianReconstruction (success case)
   - OR ReconstructionActivity generates CustodianName (partial success)
   - Activity can fail without generating any output

3. **Derivation Tracks Lineage** (`prov:wasDerivedFrom`)
   - CustodianName derives from CustodianObservation(s)
   - CustodianReconstruction derives from CustodianObservation(s)
   - Derivation is separate from Activity (tracks transformation)

4. **Confidence Measures Activity Quality**
   - Confidence attached to ReconstructionActivity (process quality)
   - NOT attached to CustodianReconstruction (result)
   - Represents: "How confident are we in this reconstruction process?"

---

## Required Changes

### 1. Move ConfidenceMeasure to ReconstructionActivity ✅

**File**: `modules/classes/ReconstructionActivity.yaml`

**Add slot**:
```yaml
slots:
  - id
  - activity_type
  - method
  - responsible_agent
  - temporal_extent
  - used  # NEW - links to CustodianObservation(s)
  - confidence_score  # NEW - moved from CustodianReconstruction
  - justification
```

**Add slot_usage**:
```yaml
slot_usage:
  used:
    slot_uri: prov:used
    description: >-
      CustodianObservation(s) used as input for this reconstruction activity.
      PROV-O: used links Activity to consumed Entities.
      Multiple observations can contribute to a single reconstruction.
    range: CustodianObservation
    multivalued: true
    required: true
  confidence_score:
    slot_uri: prov:confidence
    description: >-
      Confidence in the reconstruction activity's process and methodology.
      Measures quality of the reconstruction PROCESS, not the result.
      Range: 0.0 (low confidence) to 1.0 (high confidence).
    range: ConfidenceMeasure
    required: false
```

**Remove from**: `modules/classes/CustodianReconstruction.yaml`
- Delete `confidence_score` slot

---

### 2. Change CustodianName from Inheritance to Derivation ✅

**File**: `modules/classes/CustodianName.yaml`

**Current** (WRONG):
```yaml
CustodianName:
  is_a: CustodianObservation  # ❌ Inheritance implies "is a type of"
```

**Corrected** (RIGHT):
```yaml
CustodianName:
  # Remove is_a relationship
  class_uri: skos:Concept  # Or schema:name
  description: >-
    Standardized emic name derived from CustodianObservation(s).
    
    NOT a subclass of CustodianObservation - rather, a CustodianName is 
    DERIVED FROM observation(s) through interpretation and standardization.
    
    Can be generated by ReconstructionActivity (successful interpretation)
    or remain standalone (direct extraction without full entity resolution).
  
  slots:
    - emic_name
    - name_language
    - standardized_name
    - endorsement_source
    - was_derived_from  # NEW - links to CustodianObservation(s)
    - was_generated_by  # NEW - links to ReconstructionActivity (optional)
    - refers_to_custodian  # NEW - links to Custodian hub
    - valid_from
    - valid_to
    - supersedes
    - superseded_by
```

**Add slot_usage**:
```yaml
slot_usage:
  was_derived_from:
    slot_uri: prov:wasDerivedFrom
    description: >-
      CustodianObservation(s) from which this name was derived.
      PROV-O: wasDerivedFrom establishes observation→name derivation.
      A name can be derived from multiple observations (consolidation).
    range: CustodianObservation
    multivalued: true
    required: true
  was_generated_by:
    slot_uri: prov:wasGeneratedBy
    description: >-
      ReconstructionActivity that generated this standardized name (optional).
      If null, name was directly extracted without formal reconstruction activity.
    range: ReconstructionActivity
    required: false
  refers_to_custodian:
    slot_uri: dcterms:references
    description: >-
      The Custodian hub that this name identifies.
      Links the standardized name back to the hub.
    range: Custodian
    required: true
```

---

### 3. Add Preferred Label Link from Custodian to CustodianName ✅

**File**: `modules/classes/Custodian.yaml`

**Add slot**:
```yaml
slots:
  - hc_id
  - preferred_label  # NEW - links to primary CustodianName
  - appellations
  - identifiers
  - created
  - modified
```

**Add slot_usage**:
```yaml
slot_usage:
  preferred_label:
    slot_uri: skos:prefLabel
    description: >-
      The primary standardized emic name for this custodian.
      SKOS: prefLabel for the preferred lexical label.
      
      This is the CANONICAL name - the standardized label accepted by the 
      custodian itself for public representation.
      
      Distinct from:
      - Legal name (formal registered name in CustodianReconstruction)
      - Alternative names (in appellations)
      - Historical names (superseded CustodianNames)
    range: CustodianName
    required: false  # May be null if name not yet established
    examples:
      - value: "Rijksmuseum"
        description: "Primary emic name (not 'Stichting Rijksmuseum' legal name)"
```

---

### 4. Update CustodianObservation Documentation ✅

**File**: `modules/classes/CustodianObservation.yaml`

**Update description**:
```yaml
CustodianObservation:
  class_uri: heritage:CustodianObservation
  description: >-
    Source-based evidence of a heritage custodian's existence.
    
    CustodianObservations are INPUT ENTITIES for ReconstructionActivity:
    - Multiple observations can be reconciled into a CustodianReconstruction
    - Multiple observations can be standardized into a CustodianName
    - Observations remain independent even after reconstruction
    
    PROV-O Pattern:
      CustodianObservation → prov:used → ReconstructionActivity → prov:wasGeneratedBy → CustodianReconstruction
      CustodianObservation → prov:wasDerivedFrom ← CustodianName
```

---

## Revised Class Relationships

### Complete PROV-O Flow

```mermaid
graph TB
    subgraph Sources
        Obs1[CustodianObservation 1<br/>ISIL Registry]
        Obs2[CustodianObservation 2<br/>Museum Website]
        Obs3[CustodianObservation 3<br/>Archival Document]
    end
    
    subgraph Activity
        Act[ReconstructionActivity<br/>Entity Resolution]
        Conf[ConfidenceMeasure<br/>Score: 0.92]
    end
    
    subgraph Outputs
        Rec[CustodianReconstruction<br/>Legal Entity]
        Name[CustodianName<br/>Standardized Emic Name]
    end
    
    subgraph Hub
        Cust[Custodian Hub<br/>hc_id]
    end
    
    Obs1 -->|prov:used| Act
    Obs2 -->|prov:used| Act
    Obs3 -->|prov:used| Act
    
    Act -->|has confidence_score| Conf
    
    Act -->|prov:wasGeneratedBy| Rec
    Act -->|prov:wasGeneratedBy| Name
    
    Rec -->|prov:wasDerivedFrom| Obs1
    Rec -->|prov:wasDerivedFrom| Obs2
    
    Name -->|prov:wasDerivedFrom| Obs1
    Name -->|prov:wasDerivedFrom| Obs3
    
    Rec -->|refers_to_custodian| Cust
    Name -->|refers_to_custodian| Cust
    Obs1 -->|refers_to_custodian| Cust
    Obs2 -->|refers_to_custodian| Cust
    Obs3 -->|refers_to_custodian| Cust
    
    Cust -->|skos:prefLabel| Name
```

---

## Success vs. Failure Scenarios

### Scenario 1: Successful Full Reconstruction ✅

```yaml
# INPUT: Multiple observations
CustodianObservation:
  - id: obs-001
    observed_name: "Rijks"
    source: letterhead
  - id: obs-002
    observed_name: "Rijksmuseum Amsterdam"
    source: ISIL registry

# PROCESS: Reconstruction activity
ReconstructionActivity:
  id: act-001
  used:
    - obs-001
    - obs-002
  confidence_score:
    confidence_value: 0.95
    confidence_method: "Manual expert curation"

# OUTPUT: Both reconstruction AND standardized name
CustodianReconstruction:
  id: rec-001
  legal_name: "Stichting Rijksmuseum"
  was_derived_from: [obs-001, obs-002]
  was_generated_by: act-001
  refers_to_custodian: hc:nl-nh-ams-m-rm-q190804

CustodianName:
  id: name-001
  emic_name: "Rijksmuseum"
  was_derived_from: [obs-001, obs-002]
  was_generated_by: act-001
  refers_to_custodian: hc:nl-nh-ams-m-rm-q190804

# HUB: Links to preferred name
Custodian:
  hc_id: hc:nl-nh-ams-m-rm-q190804
  preferred_label: name-001
```

### Scenario 2: Partial Success - Name Only 🔸

```yaml
# INPUT: Single observation
CustodianObservation:
  - id: obs-003
    observed_name: "Museum van de Twintigste Eeuw"
    source: archival document

# PROCESS: Attempted reconstruction
ReconstructionActivity:
  id: act-002
  used: [obs-003]
  confidence_score:
    confidence_value: 0.45
    confidence_method: "Algorithmic matching - insufficient data"

# OUTPUT: Name only (reconstruction failed due to low confidence)
CustodianName:
  id: name-002
  emic_name: "Museum van de Twintigste Eeuw"
  was_derived_from: [obs-003]
  was_generated_by: act-002
  refers_to_custodian: hc:nl-ut-utr-m-mtwe

# NO CustodianReconstruction created (insufficient evidence)
# HUB: Still links to name
Custodian:
  hc_id: hc:nl-ut-utr-m-mtwe
  preferred_label: name-002
```

### Scenario 3: Complete Failure ❌

```yaml
# INPUT: Ambiguous observation
CustodianObservation:
  - id: obs-004
    observed_name: "Stedelijk Museum"
    source: ambiguous reference

# PROCESS: Failed reconstruction
ReconstructionActivity:
  id: act-003
  used: [obs-004]
  confidence_score:
    confidence_value: 0.15
    confidence_method: "Multiple candidate matches found"

# OUTPUT: Nothing generated (activity failed)
# NO CustodianReconstruction
# NO CustodianName
# Observation remains unresolved
```

---

## Implementation Checklist

### Phase 1: Update Core Classes

- [ ] **ReconstructionActivity.yaml**
  - [ ] Add `used` slot (CustodianObservation, multivalued)
  - [ ] Add `confidence_score` slot (ConfidenceMeasure)
  - [ ] Update documentation with PROV-O patterns

- [ ] **CustodianName.yaml**
  - [ ] Remove `is_a: CustodianObservation`
  - [ ] Add `was_derived_from` slot (CustodianObservation, multivalued)
  - [ ] Add `was_generated_by` slot (ReconstructionActivity, optional)
  - [ ] Add `refers_to_custodian` slot (Custodian)
  - [ ] Update class_uri to `skos:Concept`
  - [ ] Update documentation explaining derivation vs. inheritance

- [ ] **Custodian.yaml**
  - [ ] Add `preferred_label` slot (CustodianName)
  - [ ] Update documentation explaining preferred label usage

- [ ] **CustodianReconstruction.yaml**
  - [ ] Remove `confidence_score` slot (moved to ReconstructionActivity)
  - [ ] Update documentation clarifying it's generated by Activity

- [ ] **CustodianObservation.yaml**
  - [ ] Update documentation explaining role as Activity input
  - [ ] Add examples showing PROV-O flow

### Phase 2: Create/Update Slots

- [ ] **modules/slots/used.yaml** (NEW)
  - Create slot for `prov:used` property

- [ ] **modules/slots/preferred_label.yaml** (NEW)
  - Create slot for `skos:prefLabel` property

- [ ] **modules/slots/confidence_score.yaml** (UPDATE)
  - Move from CustodianReconstruction to ReconstructionActivity

### Phase 3: Update Main Schema

- [ ] **01_custodian_name_modular.yaml**
  - Add imports: `modules/slots/used`, `modules/slots/preferred_label`
  - Update comments explaining PROV-O pattern

### Phase 4: Documentation

- [ ] Update `HUB_ARCHITECTURE_DIAGRAM.md` with correct flow
- [ ] Create examples showing all three scenarios
- [ ] Update PROV-O alignment documentation

### Phase 5: Validation

- [ ] Run `gen-owl` to validate schema
- [ ] Create test instances for all three scenarios
- [ ] Validate RDF output
- [ ] Update UML diagrams

---

## Ontology Properties Used

### PROV-O Properties

**prov:used** (Activity → Entity):
> "A prov:Entity that was used by this prov:Activity."
- Domain: prov:Activity
- Range: prov:Entity
- Use: ReconstructionActivity uses CustodianObservation(s) as input

**prov:wasGeneratedBy** (Entity → Activity):
> "Generation is the completion of production of a new entity by an activity."
- Domain: prov:Entity
- Range: prov:Activity
- Use: CustodianReconstruction/CustodianName generated by ReconstructionActivity

**prov:wasDerivedFrom** (Entity → Entity):
> "A derivation is a transformation of an entity into another."
- Domain: prov:Entity
- Range: prov:Entity
- Use: CustodianName/CustodianReconstruction derived from CustodianObservation(s)

**prov:confidence** (Activity → ConfidenceMeasure):
> "Confidence in the activity's process or methodology."
- Extension of PROV-O
- Domain: prov:Activity
- Range: xsd:float (0.0-1.0)

### SKOS Properties

**skos:prefLabel** (Concept → Literal):
> "The preferred lexical label for a resource, in a given language."
- Domain: skos:Concept
- Range: rdfs:Literal OR CustodianName (as structured value)
- Use: Custodian.preferred_label → CustodianName

---

## Rationale

### Why CustodianName is NOT a subclass of CustodianObservation

**Conceptual Distinction**:
- **CustodianObservation**: Evidence seen in a source (emic or etic)
- **CustodianName**: Standardized interpretation of observations

**Temporal Distinction**:
- **Observation**: Records historical state ("what was written in 1920")
- **Name**: Current standardized form ("what we call it now")

**Ontological Distinction**:
- **Observation**: `pico:PersonObservation`, `crm:E73_Information_Object`
- **Name**: `skos:Concept`, `schema:name`, `rdfs:label`

**Example**:
```
Observation 1: "Rijks" (seen on letterhead, 2015)
Observation 2: "Rijksmuseum Amsterdam" (seen in ISIL registry, 2020)
Observation 3: "The Rijksmuseum" (seen in guidebook, 2018)

↓ DERIVATION (not inheritance)

CustodianName: "Rijksmuseum" (standardized emic name, 2025)
```

The name is **derived from** observations through interpretation, not a **type of** observation.

---

## References

**PROV-O Specification**:
- [PROV-O: The PROV Ontology](https://www.w3.org/TR/prov-o/)
- [PROV-O Usage Examples](https://www.w3.org/TR/prov-o/#examples)
- Local file: `/data/ontology/prov-o.rdf`

**SKOS Specification**:
- [SKOS Simple Knowledge Organization System](https://www.w3.org/TR/skos-reference/)
- prefLabel: https://www.w3.org/TR/skos-reference/#labels
- Local file: `/data/ontology/skos.rdf`

**PiCo Pattern**:
- [PiCo: Persons in Context](https://github.com/FICLIT/PiCo)
- Inspiration for observation-reconstruction pattern

---

**Status**: 🚨 AWAITING IMPLEMENTATION  
**Priority**: HIGH - Fundamental architectural fix  
**Impact**: Changes class relationships, moves properties, removes inheritance