# Country Class Implementation - Complete

**Date**: 2025-11-22  
**Session**: Continuation of FeaturePlace implementation

---

## Summary

Successfully created the **Country class** to handle country-specific feature types and legal forms.

### ✅ What Was Completed

#### 1. Fixed Duplicate Keys in FeatureTypeEnum.yaml
- **Problem**: YAML had 2 duplicate keys (RESIDENTIAL_BUILDING, SANCTUARY)
- **Resolution**:
  - Removed duplicate RESIDENTIAL_BUILDING (Q11755880) at lines 3692-3714
  - Kept Catholic-specific SANCTUARY (Q21850178 "shrine of the Catholic Church")
  - Removed generic SANCTUARY (Q29553 "sacred place")
- **Result**: 294 unique feature types (down from 296 with duplicates)

#### 2. Created Country Class
**File**: `schemas/20251121/linkml/modules/classes/Country.yaml`

**Design Philosophy**:
- **Minimal design**: ONLY ISO 3166-1 alpha-2 and alpha-3 codes
- **No other metadata**: No country names, languages, capitals, regions
- **Rationale**: ISO codes are authoritative, stable, language-neutral identifiers
- All other country metadata should be resolved via external services (GeoNames, UN M49)

**Schema**:
```yaml
Country:
  description: Country identified by ISO 3166-1 codes
  slots:
    - alpha_2  # ISO 3166-1 alpha-2 (2-letter: "NL", "PE", "US")
    - alpha_3  # ISO 3166-1 alpha-3 (3-letter: "NLD", "PER", "USA")
  
  slot_usage:
    alpha_2:
      required: true
      pattern: "^[A-Z]{2}$"
      slot_uri: schema:addressCountry
    
    alpha_3:
      required: true
      pattern: "^[A-Z]{3}$"
```

**Examples**:
- Netherlands: `alpha_2="NL"`, `alpha_3="NLD"`
- Peru: `alpha_2="PE"`, `alpha_3="PER"`
- United States: `alpha_2="US"`, `alpha_3="USA"`
- Japan: `alpha_2="JP"`, `alpha_3="JPN"`

#### 3. Integrated Country into CustodianPlace
**File**: `schemas/20251121/linkml/modules/classes/CustodianPlace.yaml`

**Changes**:
- Added `country` slot (optional, range: Country)
- Links place to its country location
- Enables country-specific feature type validation

**Use Cases**:
- Disambiguate places across countries ("Victoria Museum" exists in multiple countries)
- Enable country-conditional feature types (e.g., "cultural heritage of Peru")
- Generate country-specific enum values

**Example**:
```yaml
CustodianPlace:
  place_name: "Machu Picchu"
  place_language: "es"
  country:
    alpha_2: "PE"
    alpha_3: "PER"
  has_feature_type:
    feature_type: CULTURAL_HERITAGE_OF_PERU  # Only valid for PE!
```

#### 4. Integrated Country into LegalForm
**File**: `schemas/20251121/linkml/modules/classes/LegalForm.yaml`

**Changes**:
- Updated `country_code` from string pattern to Country class reference
- Enforces jurisdiction-specific legal forms via ontology links

**Rationale**:
- Legal forms are jurisdiction-specific
- A "Stichting" in Netherlands ≠ "Fundación" in Spain (different legal meaning)
- Country class provides canonical ISO codes for legal jurisdictions

**Before** (string):
```yaml
country_code:
  range: string
  pattern: "^[A-Z]{2}$"
```

**After** (Country class):
```yaml
country_code:
  range: Country
  required: true
```

**Example**:
```yaml
LegalForm:
  elf_code: "8888"
  country_code:
    alpha_2: "NL"
    alpha_3: "NLD"
  local_name: "Stichting"
  abbreviation: "Stg."
```

#### 5. Created Example Instance File
**File**: `schemas/20251121/examples/country_integration_example.yaml`

Shows:
- Country instances (NL, PE, US)
- CustodianPlace with country linking
- LegalForm with country linking
- Country-specific feature types (CULTURAL_HERITAGE_OF_PERU, BUITENPLAATS)

---

## Design Decisions

### Why Minimal Country Class?

**Excluded Metadata**:
- ❌ Country names (language-dependent: "Netherlands" vs "Pays-Bas" vs "荷兰")
- ❌ Capital cities (change over time: Myanmar moved capital 2006)
- ❌ Languages (multilingual countries: Belgium has 3 official languages)
- ❌ Regions/continents (political: Is Turkey in Europe or Asia?)
- ❌ Currency (changes: Eurozone adoption)
- ❌ Phone codes (technical, not heritage-relevant)

**Rationale**:
1. **Language neutrality**: ISO codes work across all languages
2. **Temporal stability**: Country names and capitals change; ISO codes are persistent
3. **Separation of concerns**: Heritage ontology shouldn't duplicate geopolitical databases
4. **External resolution**: Use GeoNames, UN M49, or ISO 3166 Maintenance Agency for metadata

**External Services**:
- GeoNames API: Country names in 20+ languages, capitals, regions
- UN M49: Standard country codes and regions
- ISO 3166 Maintenance Agency: Official ISO code updates

### Why Both Alpha-2 and Alpha-3?

**Alpha-2** (2-letter):
- Used by: Internet ccTLDs (.nl, .pe, .us), Schema.org addressCountry
- Compact, widely recognized
- **Primary for web applications**

**Alpha-3** (3-letter):
- Used by: United Nations, International Olympic Committee, ISO 4217 (currency codes)
- Less ambiguous (e.g., "AT" = Austria vs "AT" = @-sign in some systems)
- **Primary for international standards**

**Both are required** to ensure interoperability across different systems.

---

## Country-Specific Feature Types

### Problem: Some feature types only apply to specific countries

**Examples from FeatureTypeEnum.yaml**:

1. **CULTURAL_HERITAGE_OF_PERU** (Q16617058)
   - Description: "cultural heritage of Peru"
   - Only valid for: `country.alpha_2 = "PE"`
   - Hypernym: cultural heritage

2. **BUITENPLAATS** (Q2927789)
   - Description: "summer residence for rich townspeople in the Netherlands"
   - Only valid for: `country.alpha_2 = "NL"`
   - Hypernym: heritage site

3. **NATIONAL_MEMORIAL_OF_THE_UNITED_STATES** (Q20010800)
   - Description: "national memorial in the United States"
   - Only valid for: `country.alpha_2 = "US"`
   - Hypernym: heritage site

### Solution: Country-Conditional Enum Values

**Implementation Strategy**:

When validating CustodianPlace.has_feature_type:
```python
place_country = custodian_place.country.alpha_2

if feature_type == "CULTURAL_HERITAGE_OF_PERU":
    assert place_country == "PE", "CULTURAL_HERITAGE_OF_PERU only valid for Peru"

if feature_type == "BUITENPLAATS":
    assert place_country == "NL", "BUITENPLAATS only valid for Netherlands"
```

**LinkML Implementation** (future enhancement):
```yaml
FeatureTypeEnum:
  permissible_values:
    CULTURAL_HERITAGE_OF_PERU:
      meaning: wd:Q16617058
      annotations:
        country_restriction: "PE"  # Only valid for Peru
    
    BUITENPLAATS:
      meaning: wd:Q2927789
      annotations:
        country_restriction: "NL"  # Only valid for Netherlands
```

---

## Files Modified

### Created:
1. `schemas/20251121/linkml/modules/classes/Country.yaml` (new)
2. `schemas/20251121/examples/country_integration_example.yaml` (new)

### Modified:
3. `schemas/20251121/linkml/modules/classes/CustodianPlace.yaml`
   - Added `country` import
   - Added `country` slot
   - Added slot_usage documentation

4. `schemas/20251121/linkml/modules/classes/LegalForm.yaml`
   - Added `Country` import
   - Changed `country_code` from string to Country class reference

5. `schemas/20251121/linkml/modules/enums/FeatureTypeEnum.yaml`
   - Removed duplicate RESIDENTIAL_BUILDING (Q11755880)
   - Removed duplicate SANCTUARY (Q29553, kept Q21850178)
   - Result: 294 unique feature types

---

## Validation Results

### YAML Syntax: ✅ Valid
```
Total enum values: 294
No duplicate keys found
```

### Country Class: ✅ Minimal Design
```
- alpha_2: Required, pattern: ^[A-Z]{2}$
- alpha_3: Required, pattern: ^[A-Z]{3}$
- No other fields (names, languages, capitals excluded)
```

### Integration: ✅ Complete
- CustodianPlace → Country (optional link)
- LegalForm → Country (required link, jurisdiction-specific)
- FeatureTypeEnum → Ready for country-conditional validation

---

## Next Steps (Future Work)

### 1. Country-Conditional Enum Validation
**Task**: Implement validation rules for country-specific feature types

**Approach**:
- Add `country_restriction` annotation to FeatureTypeEnum entries
- Create LinkML validation rule to check CustodianPlace.country matches restriction
- Generate country-specific enum subsets for UI dropdowns

**Example Rule**:
```yaml
rules:
  - title: "Country-specific feature type validation"
    preconditions:
      slot_conditions:
        has_feature_type:
          range: FeaturePlace
    postconditions:
      slot_conditions:
        country:
          value_must_match: "{has_feature_type.country_restriction}"
```

### 2. Populate Country Instances
**Task**: Create Country instances for all countries in the dataset

**Data Source**: ISO 3166-1 official list (249 countries)

**Implementation**:
```yaml
# schemas/20251121/data/countries.yaml
countries:
  - id: https://nde.nl/ontology/hc/country/NL
    alpha_2: "NL"
    alpha_3: "NLD"
  
  - id: https://nde.nl/ontology/hc/country/PE
    alpha_2: "PE"
    alpha_3: "PER"
  
  # ... 247 more entries
```

### 3. Link LegalForm to ISO 20275 ELF Codes
**Task**: Populate LegalForm instances with ISO 20275 Entity Legal Form codes

**Data Source**: GLEIF ISO 20275 Code List (1,600+ legal forms across 150+ jurisdictions)

**Example**:
```yaml
# Netherlands legal forms
- id: https://nde.nl/ontology/hc/legal-form/nl-8888
  elf_code: "8888"
  country_code: {alpha_2: "NL", alpha_3: "NLD"}
  local_name: "Stichting"
  abbreviation: "Stg."

- id: https://nde.nl/ontology/hc/legal-form/nl-akd2
  elf_code: "AKD2"
  country_code: {alpha_2: "NL", alpha_3: "NLD"}
  local_name: "Besloten vennootschap"
  abbreviation: "B.V."
```

### 4. External Resolution Service Integration
**Task**: Provide helper functions to resolve country metadata via GeoNames API

**Implementation**:
```python
from typing import Dict
import requests

def resolve_country_metadata(alpha_2: str) -> Dict:
    """Resolve country metadata from GeoNames API."""
    url = f"http://api.geonames.org/countryInfoJSON"
    params = {
        "country": alpha_2,
        "username": "your_geonames_username"
    }
    response = requests.get(url, params=params)
    data = response.json()
    
    return {
        "name_en": data["geonames"][0]["countryName"],
        "capital": data["geonames"][0]["capital"],
        "languages": data["geonames"][0]["languages"].split(","),
        "continent": data["geonames"][0]["continent"]
    }

# Usage
country_metadata = resolve_country_metadata("NL")
# Returns: {
#   "name_en": "Netherlands",
#   "capital": "Amsterdam",
#   "languages": ["nl", "fy"],
#   "continent": "EU"
# }
```

### 5. UI Dropdown Generation
**Task**: Generate country-filtered feature type dropdowns for data entry forms

**Use Case**: When user selects "Netherlands" as country, only show:
- Universal feature types (MUSEUM, CHURCH, MANSION, etc.)
- Netherlands-specific types (BUITENPLAATS)
- Exclude Peru-specific types (CULTURAL_HERITAGE_OF_PERU)

**Implementation**:
```python
def get_valid_feature_types(country_alpha_2: str) -> List[str]:
    """Get valid feature types for a given country."""
    universal_types = [ft for ft in FeatureTypeEnum if not has_country_restriction(ft)]
    country_specific = [ft for ft in FeatureTypeEnum if get_country_restriction(ft) == country_alpha_2]
    return universal_types + country_specific
```

---

## References

- **ISO 3166-1**: https://www.iso.org/iso-3166-country-codes.html
- **GeoNames API**: https://www.geonames.org/export/web-services.html
- **UN M49**: https://unstats.un.org/unsd/methodology/m49/
- **ISO 20275**: https://www.gleif.org/en/about-lei/code-lists/iso-20275-entity-legal-forms-code-list
- **Schema.org addressCountry**: https://schema.org/addressCountry
- **Wikidata Q-numbers**: Country-specific heritage feature types

---

## Status

✅ **Country Class Implementation: COMPLETE**

- [x] Duplicate keys fixed in FeatureTypeEnum.yaml
- [x] Country class created with minimal design
- [x] CustodianPlace integrated with country linking
- [x] LegalForm integrated with country linking
- [x] Example instance file created
- [x] Documentation complete

**Ready for**: Country-conditional enum validation and LegalForm population with ISO 20275 codes.