# SHACL Validation Shapes for Heritage Custodian Ontology

**Version**: 1.0.0  
**Schema Version**: v0.7.0  
**Created**: 2025-11-22  
**SHACL Spec**: https://www.w3.org/TR/shacl/

---

## Table of Contents

1. [Overview](#overview)
2. [Installation](#installation)
3. [Usage](#usage)
4. [Validation Rules](#validation-rules)
5. [Shape Definitions](#shape-definitions)
6. [Examples](#examples)
7. [Integration](#integration)
8. [Comparison with Python Validator](#comparison-with-python-validator)

---

## Overview

This document describes the **SHACL (Shapes Constraint Language)** validation shapes for the Heritage Custodian Ontology. SHACL shapes enforce data quality constraints at RDF ingestion time, preventing invalid data from entering triple stores.

### What is SHACL?

**SHACL** is a W3C recommendation for validating RDF graphs against a set of conditions (shapes). Unlike SPARQL queries that **detect** violations after data is stored, SHACL shapes **prevent** violations during data loading.

### Benefits of SHACL Validation

✅ **Prevention over Detection**: Reject invalid data before storage  
✅ **Standardized Reports**: Machine-readable validation results  
✅ **Triple Store Integration**: Native support in GraphDB, Jena, Virtuoso  
✅ **Declarative Constraints**: Express rules in RDF (no external scripts)  
✅ **Detailed Error Messages**: Precise identification of failing triples  

---

## Installation

### Prerequisites

Install Python dependencies:

```bash
pip install pyshacl rdflib
```

**Libraries**:
- **pyshacl** (v0.25.0+): SHACL validator for Python
- **rdflib** (v7.0.0+): RDF graph library

### Verify Installation

```bash
python3 -c "import pyshacl; print(pyshacl.__version__)"
# Expected output: 0.25.0 (or later)
```

---

## Usage

### Command Line Validation

**Basic Usage**:
```bash
python scripts/validate_with_shacl.py data.ttl
```

**With Custom Shapes**:
```bash
python scripts/validate_with_shacl.py data.ttl --shapes custom_shapes.ttl
```

**Different RDF Formats**:
```bash
# JSON-LD data
python scripts/validate_with_shacl.py data.jsonld --format jsonld

# N-Triples data
python scripts/validate_with_shacl.py data.nt --format nt
```

**Save Validation Report**:
```bash
python scripts/validate_with_shacl.py data.ttl --output report.ttl
```

**Verbose Output**:
```bash
python scripts/validate_with_shacl.py data.ttl --verbose
```

### Python Library Usage

```python
from scripts.validate_with_shacl import validate_file

# Validate with default shapes
if validate_file("data.ttl"):
    print("✅ Data is valid")
else:
    print("❌ Data has violations")

# Validate with custom shapes
if validate_file("data.ttl", shapes_file="custom_shapes.ttl"):
    print("✅ Valid")
```

### Triple Store Integration

**Apache Jena Fuseki**:
```bash
# Load shapes into Fuseki dataset
tdbloader2 --loc=/path/to/tdb custodian_validation_shapes.ttl

# Validate data during SPARQL UPDATE
# Fuseki automatically applies SHACL validation if shapes are loaded
```

**GraphDB**:
1. Create repository with SHACL validation enabled
2. Import shapes file into dedicated context: `http://shacl/shapes`
3. GraphDB validates all data changes automatically

---

## Validation Rules

This SHACL shapes file implements **5 core validation rules** from Phase 5:

| Rule ID | Name | Severity | Description |
|---------|------|----------|-------------|
| **Rule 1** | Collection-Unit Temporal Consistency | ERROR | Collection custody dates must fall within managing unit's validity period |
| **Rule 2** | Collection-Unit Bidirectional | ERROR | Collection → unit must have inverse unit → collection |
| **Rule 3** | Custody Transfer Continuity | WARNING | Custody transfers must be continuous (no gaps/overlaps) |
| **Rule 4** | Staff-Unit Temporal Consistency | ERROR | Staff employment dates must fall within unit's validity period |
| **Rule 5** | Staff-Unit Bidirectional | ERROR | Person → unit must have inverse unit → person |

Plus **3 additional shapes** for type and format constraints.

---

## Shape Definitions

### Rule 1: Collection-Unit Temporal Consistency

**Shape ID**: `custodian:CollectionUnitTemporalConsistencyShape`

**Target**: All instances of `custodian:CustodianCollection`

**Constraints**:

#### Constraint 1.1: Collection Starts After Unit Founding

```turtle
sh:sparql [
    sh:message "Collection valid_from ({?collectionStart}) must be >= managing unit valid_from ({?unitStart})" ;
    sh:select """
        SELECT $this ?collectionStart ?unitStart ?managingUnit
        WHERE {
            $this custodian:managing_unit ?managingUnit ;
                  custodian:valid_from ?collectionStart .
            
            ?managingUnit custodian:valid_from ?unitStart .
            
            # VIOLATION: Collection starts before unit exists
            FILTER(?collectionStart < ?unitStart)
        }
    """ ;
] .
```

**Example Violation**:
```turtle
# Unit founded 2010
<https://example.org/unit/dept-1>
    a custodian:OrganizationalStructure ;
    custodian:valid_from "2010-01-01"^^xsd:date .

# Collection started 2005 (INVALID!)
<https://example.org/collection/col-1>
    a custodian:CustodianCollection ;
    custodian:managing_unit <https://example.org/unit/dept-1> ;
    custodian:valid_from "2005-01-01"^^xsd:date .
```

**Violation Report**:
```
❌ Validation Result [Constraint Component: sh:SPARQLConstraintComponent]
    Severity: sh:Violation
    Message: Collection valid_from (2005-01-01) must be >= managing unit valid_from (2010-01-01)
    Focus Node: https://example.org/collection/col-1
```

---

#### Constraint 1.2: Collection Ends Before Unit Dissolution

```turtle
sh:sparql [
    sh:message "Collection valid_to ({?collectionEnd}) must be <= managing unit valid_to ({?unitEnd})" ;
    sh:select """
        SELECT $this ?collectionEnd ?unitEnd ?managingUnit
        WHERE {
            $this custodian:managing_unit ?managingUnit ;
                  custodian:valid_to ?collectionEnd .
            
            ?managingUnit custodian:valid_to ?unitEnd .
            
            # Unit is dissolved
            FILTER(BOUND(?unitEnd))
            
            # VIOLATION: Collection custody ends after unit dissolution
            FILTER(?collectionEnd > ?unitEnd)
        }
    """ ;
] .
```

**Example Violation**:
```turtle
# Unit dissolved 2020
<https://example.org/unit/dept-1>
    a custodian:OrganizationalStructure ;
    custodian:valid_from "2010-01-01"^^xsd:date ;
    custodian:valid_to "2020-12-31"^^xsd:date .

# Collection custody ended 2023 (INVALID!)
<https://example.org/collection/col-1>
    a custodian:CustodianCollection ;
    custodian:managing_unit <https://example.org/unit/dept-1> ;
    custodian:valid_from "2015-01-01"^^xsd:date ;
    custodian:valid_to "2023-06-01"^^xsd:date .
```

---

#### Warning: Ongoing Custody After Unit Dissolution

```turtle
sh:sparql [
    sh:severity sh:Warning ;
    sh:message "Collection has ongoing custody but managing unit was dissolved" ;
    sh:select """
        SELECT $this ?managingUnit ?unitEnd
        WHERE {
            $this custodian:managing_unit ?managingUnit .
            
            # Collection has no end date (ongoing)
            FILTER NOT EXISTS { $this custodian:valid_to ?collectionEnd }
            
            # But unit is dissolved
            ?managingUnit custodian:valid_to ?unitEnd .
        }
    """ ;
] .
```

**Example Warning**:
```turtle
# Unit dissolved 2020
<https://example.org/unit/dept-1>
    custodian:valid_to "2020-12-31"^^xsd:date .

# Collection custody ongoing (WARNING!)
<https://example.org/collection/col-1>
    custodian:managing_unit <https://example.org/unit/dept-1> ;
    custodian:valid_from "2015-01-01"^^xsd:date .
    # No valid_to → custody still active
```

**Interpretation**: Collection likely transferred to another unit but custody history not updated.

---

### Rule 2: Collection-Unit Bidirectional Relationships

**Shape ID**: `custodian:CollectionUnitBidirectionalShape`

**Target**: All instances of `custodian:CustodianCollection`

**Constraint**: If collection references `managing_unit`, unit must reference collection in `managed_collections`.

```turtle
sh:sparql [
    sh:message "Collection references managing_unit {?unit} but unit does not list collection in managed_collections" ;
    sh:select """
        SELECT $this ?unit
        WHERE {
            $this custodian:managing_unit ?unit .
            
            # VIOLATION: Unit does not reference collection back
            FILTER NOT EXISTS {
                ?unit custodian:managed_collections $this
            }
        }
    """ ;
] .
```

**Example Violation**:
```turtle
# Collection references unit
<https://example.org/collection/col-1>
    custodian:managing_unit <https://example.org/unit/dept-1> .

# But unit does NOT reference collection (INVALID!)
<https://example.org/unit/dept-1>
    a custodian:OrganizationalStructure .
    # Missing: custodian:managed_collections <https://example.org/collection/col-1>
```

**Fix**:
```turtle
# Add inverse relationship
<https://example.org/unit/dept-1>
    custodian:managed_collections <https://example.org/collection/col-1> .
```

---

### Rule 3: Custody Transfer Continuity

**Shape ID**: `custodian:CustodyTransferContinuityShape`

**Target**: All instances of `custodian:CustodianCollection`

**Constraints**:

#### Check for Gaps in Custody Chain

```turtle
sh:sparql [
    sh:severity sh:Warning ;
    sh:message "Custody gap detected: previous custody ended on {?prevEnd} but next custody started on {?nextStart}" ;
    sh:select """
        SELECT $this ?prevEnd ?nextStart ?gapDays
        WHERE {
            $this custodian:custody_history ?event1 ;
                  custodian:custody_history ?event2 .
            
            ?event1 custodian:transfer_date ?prevEnd .
            ?event2 custodian:transfer_date ?nextStart .
            
            FILTER(?nextStart > ?prevEnd)
            BIND((xsd:date(?nextStart) - xsd:date(?prevEnd)) AS ?gapDays)
            
            # WARNING: Gap > 1 day
            FILTER(?gapDays > 1)
        }
    """ ;
] .
```

**Example Warning**:
```turtle
<https://example.org/collection/col-1>
    custodian:custody_history <https://example.org/event/transfer-1> ;
    custodian:custody_history <https://example.org/event/transfer-2> .

<https://example.org/event/transfer-1>
    custodian:transfer_date "2010-01-01"^^xsd:date .

<https://example.org/event/transfer-2>
    custodian:transfer_date "2010-02-01"^^xsd:date .
    # Gap of 31 days between transfers
```

---

#### Check for Overlaps in Custody Chain

```turtle
sh:sparql [
    sh:message "Custody overlap detected: collection managed by {?custodian1} until {?end1} and simultaneously by {?custodian2} from {?start2}" ;
    sh:select """
        SELECT $this ?custodian1 ?end1 ?custodian2 ?start2
        WHERE {
            $this custodian:custody_history ?event1 ;
                  custodian:custody_history ?event2 .
            
            ?event1 custodian:new_custodian ?custodian1 ;
                    custodian:custody_end_date ?end1 .
            
            ?event2 custodian:new_custodian ?custodian2 ;
                    custodian:transfer_date ?start2 .
            
            FILTER(?custodian1 != ?custodian2)
            FILTER(?start2 < ?end1)  # Overlap!
        }
    """ ;
] .
```

---

### Rule 4: Staff-Unit Temporal Consistency

**Shape ID**: `custodian:StaffUnitTemporalConsistencyShape`

**Target**: All instances of `custodian:PersonObservation`

**Constraints**: Same as Rule 1, but for staff employment dates vs. unit validity period.

#### Constraint 4.1: Employment Starts After Unit Founding

```turtle
sh:sparql [
    sh:message "Staff employment_start_date ({?employmentStart}) must be >= unit valid_from ({?unitStart})" ;
    sh:select """
        SELECT $this ?employmentStart ?unitStart ?unit
        WHERE {
            $this custodian:unit_affiliation ?unit ;
                  custodian:employment_start_date ?employmentStart .
            
            ?unit custodian:valid_from ?unitStart .
            
            FILTER(?employmentStart < ?unitStart)
        }
    """ ;
] .
```

**Example Violation**:
```turtle
# Unit founded 2015
<https://example.org/unit/dept-1>
    custodian:valid_from "2015-01-01"^^xsd:date .

# Staff employed 2010 (INVALID!)
<https://example.org/person/john-doe>
    custodian:unit_affiliation <https://example.org/unit/dept-1> ;
    custodian:employment_start_date "2010-01-01"^^xsd:date .
```

---

### Rule 5: Staff-Unit Bidirectional Relationships

**Shape ID**: `custodian:StaffUnitBidirectionalShape`

**Target**: All instances of `custodian:PersonObservation`

**Constraint**: If person references `unit_affiliation`, unit must reference person in `staff_members` or `org:hasMember`.

```turtle
sh:sparql [
    sh:message "Person references unit_affiliation {?unit} but unit does not list person in staff_members" ;
    sh:select """
        SELECT $this ?unit
        WHERE {
            $this custodian:unit_affiliation ?unit .
            
            # VIOLATION: Unit does not reference person back
            FILTER NOT EXISTS {
                { ?unit custodian:staff_members $this }
                UNION
                { ?unit org:hasMember $this }
            }
        }
    """ ;
] .
```

---

### Additional Shapes: Type and Format Constraints

#### Type Constraint: managing_unit Must Be OrganizationalStructure

```turtle
custodian:CollectionManagingUnitTypeShape
    sh:property [
        sh:path custodian:managing_unit ;
        sh:class custodian:OrganizationalStructure ;
        sh:message "managing_unit must be an instance of OrganizationalStructure" ;
    ] .
```

#### Type Constraint: unit_affiliation Must Be OrganizationalStructure

```turtle
custodian:PersonUnitAffiliationTypeShape
    sh:property [
        sh:path custodian:unit_affiliation ;
        sh:class custodian:OrganizationalStructure ;
        sh:message "unit_affiliation must be an instance of OrganizationalStructure" ;
    ] .
```

#### Format Constraint: Dates Must Be xsd:date or xsd:dateTime

```turtle
custodian:DatetimeFormatShape
    sh:property [
        sh:path custodian:valid_from ;
        sh:or (
            [ sh:datatype xsd:date ]
            [ sh:datatype xsd:dateTime ]
        ) ;
    ] .
```

---

## Examples

### Example 1: Valid Collection-Unit Relationship

**Valid RDF Data**:
```turtle
@prefix custodian: <https://nde.nl/ontology/hc/custodian/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<https://example.org/unit/paintings-dept>
    a custodian:OrganizationalStructure ;
    custodian:unit_name "Paintings Department" ;
    custodian:valid_from "1985-01-01"^^xsd:date ;
    custodian:managed_collections <https://example.org/collection/dutch-paintings> .

<https://example.org/collection/dutch-paintings>
    a custodian:CustodianCollection ;
    custodian:collection_name "Dutch Paintings" ;
    custodian:managing_unit <https://example.org/unit/paintings-dept> ;
    custodian:valid_from "1995-01-01"^^xsd:date .
```

**Validation**:
```bash
python scripts/validate_with_shacl.py valid_data.ttl
# ✅ VALIDATION PASSED
# No constraint violations found.
```

---

### Example 2: Invalid - Temporal Violation

**Invalid RDF Data**:
```turtle
<https://example.org/unit/paintings-dept>
    custodian:valid_from "1985-01-01"^^xsd:date .

<https://example.org/collection/dutch-paintings>
    custodian:managing_unit <https://example.org/unit/paintings-dept> ;
    custodian:valid_from "1970-01-01"^^xsd:date .  # Before unit exists!
```

**Validation**:
```bash
python scripts/validate_with_shacl.py invalid_data.ttl
# ❌ VALIDATION FAILED
# 
# Constraint Violations:
# --------------------------------------------------------------------------------
# Validation Result [Constraint Component: sh:SPARQLConstraintComponent]:
#     Severity: sh:Violation
#     Message: Collection valid_from (1970-01-01) must be >= managing unit valid_from (1985-01-01)
#     Focus Node: https://example.org/collection/dutch-paintings
#     Result Path: -
#     Source Shape: custodian:CollectionUnitTemporalConsistencyShape
```

---

### Example 3: Invalid - Missing Bidirectional Relationship

**Invalid RDF Data**:
```turtle
<https://example.org/collection/dutch-paintings>
    custodian:managing_unit <https://example.org/unit/paintings-dept> .

<https://example.org/unit/paintings-dept>
    a custodian:OrganizationalStructure .
    # Missing: custodian:managed_collections <https://example.org/collection/dutch-paintings>
```

**Validation**:
```bash
python scripts/validate_with_shacl.py invalid_data.ttl
# ❌ VALIDATION FAILED
# 
# Constraint Violations:
# --------------------------------------------------------------------------------
# Validation Result:
#     Severity: sh:Violation
#     Message: Collection references managing_unit https://example.org/unit/paintings-dept
#              but unit does not list collection in managed_collections
#     Focus Node: https://example.org/collection/dutch-paintings
```

---

## Integration

### CI/CD Pipeline Integration

**GitHub Actions Example**:
```yaml
name: SHACL Validation

on: [push, pull_request]

jobs:
  validate:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      
      - name: Set up Python
        uses: actions/setup-python@v4
        with:
          python-version: '3.10'
      
      - name: Install dependencies
        run: pip install pyshacl rdflib
      
      - name: Validate RDF data
        run: |
          python scripts/validate_with_shacl.py data/instances/*.ttl
      
      - name: Upload validation report
        if: failure()
        uses: actions/upload-artifact@v3
        with:
          name: validation-report
          path: validation_report.ttl
```

---

### Pre-commit Hook

**`.git/hooks/pre-commit`**:
```bash
#!/bin/bash
# Validate RDF files before commit

echo "Running SHACL validation..."

for file in data/instances/*.ttl; do
    python scripts/validate_with_shacl.py "$file" --quiet
    if [ $? -ne 0 ]; then
        echo "❌ SHACL validation failed for $file"
        echo "Fix violations before committing."
        exit 1
    fi
done

echo "✅ All files pass SHACL validation"
exit 0
```

---

## Comparison with Python Validator

### Phase 5 Python Validator vs. Phase 7 SHACL Shapes

| Aspect | Python Validator (Phase 5) | SHACL Shapes (Phase 7) |
|--------|---------------------------|------------------------|
| **Input Format** | YAML (LinkML instances) | RDF (Turtle, JSON-LD, etc.) |
| **Execution** | Standalone script | Triple store integrated OR pyshacl |
| **Performance** | Fast for <1,000 records | Optimized for >10,000 records |
| **Deployment** | Python runtime required | RDF triple store native |
| **Error Messages** | Custom CLI output | Standardized SHACL reports |
| **CI/CD** | Exit codes (0/1/2) | Exit codes (0/1/2) + RDF report |
| **Use Case** | Development validation | Production runtime validation |

### When to Use Which?

**Use Python Validator** (`validate_temporal_consistency.py`):
- ✅ During schema development (fast feedback on YAML instances)
- ✅ Pre-commit hooks for LinkML files
- ✅ Unit testing LinkML examples
- ✅ Before RDF conversion

**Use SHACL Shapes** (`validate_with_shacl.py`):
- ✅ Production RDF triple stores (GraphDB, Fuseki)
- ✅ Data ingestion pipelines
- ✅ Continuous monitoring (real-time validation)
- ✅ After RDF conversion (final quality gate)

**Best Practice**: Use **both**:
1. Python validator during development (YAML → validate → RDF)
2. SHACL shapes in production (RDF → validate → store)

---

## Advanced Usage

### Generate Validation Report

```bash
python scripts/validate_with_shacl.py data.ttl --output report.ttl
```

**Report Format** (Turtle):
```turtle
@prefix sh: <http://www.w3.org/ns/shacl#> .

[ a sh:ValidationReport ;
    sh:conforms false ;
    sh:result [
        a sh:ValidationResult ;
        sh:focusNode <https://example.org/collection/col-1> ;
        sh:resultMessage "Collection valid_from (1970-01-01) must be >= ..." ;
        sh:resultSeverity sh:Violation ;
        sh:sourceConstraintComponent sh:SPARQLConstraintComponent ;
        sh:sourceShape custodian:CollectionUnitTemporalConsistencyShape
    ]
] .
```

---

### Custom Severity Levels

SHACL supports three severity levels:

```turtle
sh:severity sh:Violation ;  # ERROR (blocks data loading)
sh:severity sh:Warning ;    # WARNING (logged but allowed)
sh:severity sh:Info ;       # INFO (informational only)
```

**Example**: Custody gap is a **warning** (data quality issue but not invalid):
```turtle
custodian:CustodyTransferContinuityShape
    sh:sparql [
        sh:severity sh:Warning ;  # Allow data but log warning
        sh:message "Custody gap detected..." ;
        ...
    ] .
```

---

### Extending Shapes

Add custom validation rules by creating new shapes:

```turtle
# Custom rule: Collection name must not be empty
custodian:CollectionNameNotEmptyShape
    a sh:NodeShape ;
    sh:targetClass custodian:CustodianCollection ;
    sh:property [
        sh:path custodian:collection_name ;
        sh:minLength 1 ;
        sh:message "Collection name must not be empty" ;
    ] .
```

---

## Troubleshooting

### Common Issues

#### Issue 1: "pyshacl not found"

**Solution**:
```bash
pip install pyshacl rdflib
```

#### Issue 2: "Parse error: Invalid Turtle syntax"

**Solution**: Validate RDF syntax first:
```bash
rdfpipe -i turtle data.ttl > /dev/null
# If errors, fix syntax before SHACL validation
```

#### Issue 3: "No violations found but data is clearly invalid"

**Solution**: Check namespace prefixes match between shapes and data:
```turtle
# Shapes file uses:
@prefix custodian: <https://nde.nl/ontology/hc/custodian/> .

# Data file must use same namespace:
<https://nde.nl/ontology/hc/custodian/CustodianCollection>
```

---

## References

- **SHACL Specification**: https://www.w3.org/TR/shacl/
- **pyshacl Documentation**: https://github.com/RDFLib/pySHACL
- **SHACL Advanced Features**: https://www.w3.org/TR/shacl-af/
- **Python Validator (Phase 5)**: `scripts/validate_temporal_consistency.py`
- **SPARQL Queries (Phase 6)**: `docs/SPARQL_QUERIES_ORGANIZATIONAL.md`
- **Schema (v0.7.0)**: `schemas/20251121/linkml/01_custodian_name_modular.yaml`

---

## Next Steps

### Phase 8: LinkML Schema Constraints

Embed validation rules directly into LinkML schema using:
- `minimum_value` / `maximum_value` for date comparisons
- `pattern` for format validation
- Custom validators with Python functions
- Slot-level constraints

**Goal**: Validate at **schema definition** level, not just RDF level.

---

**Document Version**: 1.0.0  
**Schema Version**: v0.7.0  
**Last Updated**: 2025-11-22  
**SHACL Shapes File**: `schemas/20251121/shacl/custodian_validation_shapes.ttl` (474 lines)  
**Validation Script**: `scripts/validate_with_shacl.py` (289 lines)