# Rule 51: No Hallucinated Ontology References

**Priority**: CRITICAL  
**Scope**: All LinkML schema files (`schemas/20251121/linkml/`)  
**Created**: 2025-01-13

---

## Summary

All ontology references in LinkML schema files (`class_uri`, `slot_uri`, `*_mappings`) MUST be verifiable against actual ontology files in `/data/ontology/`. References to predicates or classes that do not exist in local ontology files are considered **hallucinated** and are prohibited.

---

## The Problem

AI agents may suggest ontology mappings based on training data without verifying that:
1. The ontology file exists in `/data/ontology/`
2. The specific predicate/class exists within that ontology file
3. The prefix is declared and resolvable

This leads to schema files containing references like `dqv:value` or `adms:status` that cannot be validated or serialized to RDF.

---

## Requirements

### 1. All Ontology Prefixes Must Have Local Files

Before using a prefix (e.g., `prov:`, `schema:`, `org:`), verify the ontology file exists:

```bash
# Check if ontology exists
ls data/ontology/ | grep -i "prov\|schema\|org"
```

**Available Ontologies** (as of 2025-01-13):

| Prefix | File | Verified |
|--------|------|----------|
| `prov:` | `prov-o.ttl`, `prov.ttl` | ✅ |
| `schema:` | `schemaorg.owl` | ✅ |
| `org:` | `org.rdf` | ✅ |
| `skos:` | `skos.rdf` | ✅ |
| `dcterms:` | `dublin_core_elements.rdf` | ✅ |
| `foaf:` | `foaf.ttl` | ✅ |
| `rico:` | `RiC-O_1-1.rdf` | ✅ |
| `crm:` | `CIDOC_CRM_v7.1.3.rdf` | ✅ |
| `geo:` | `geo.ttl` | ✅ |
| `sosa:` | `sosa.ttl` | ✅ |
| `bf:` | `bibframe.rdf` | ✅ |
| `edm:` | `edm.owl` | ✅ |
| `premis:` | `premis3.owl` | ✅ |
| `dcat:` | `dcat3.ttl` | ✅ |
| `ore:` | `ore.rdf` | ✅ |
| `pico:` | `pico.ttl` | ✅ |
| `gn:` | `geonames_ontology.rdf` | ✅ |
| `time:` | `time.ttl` | ✅ |
| `locn:` | `locn.ttl` | ✅ |
| `dqv:` | `dqv.ttl` | ✅ |
| `adms:` | `adms.ttl` | ✅ |

**NOT Available** (do not use without adding):

| Prefix | Status | Alternative |
|--------|--------|-------------|
| `qudt:` | Only referenced in era_ontology.ttl | Use `hc:` with close_mappings annotation |

### 2. Predicates Must Exist in Ontology Files

Before using a predicate, verify it exists:

```bash
# Verify predicate exists
grep -l "hasFrameRate\|frameRate" data/ontology/premis3.owl

# Check specific predicate definition
grep -E "premis:hasFrameRate|:hasFrameRate" data/ontology/premis3.owl
```

### 3. Use hc: Prefix for Domain-Specific Concepts

When no standard ontology predicate exists, use the Heritage Custodian namespace:

```yaml
# CORRECT - Use hc: with documentation
slots:
  heritage_relevance_score:
    slot_uri: hc:heritageRelevanceScore
    description: Heritage sector relevance score (0.0-1.0)
    annotations:
      ontology_note: >-
        No standard ontology predicate for heritage relevance scoring.
        Domain-specific metric for this project.

# WRONG - Hallucinated predicate
slots:
  heritage_relevance_score:
    slot_uri: dqv:heritageScore  # Does not exist!
```

### 4. Document External References in close_mappings

When a similar concept exists in an ontology we don't have locally, document it in `close_mappings` with a note:

```yaml
slots:
  confidence_score:
    slot_uri: hc:confidenceScore
    close_mappings:
      - dqv:value  # W3C Data Quality Vocabulary (not in local files)
    annotations:
      external_ontology_note: >-
        dqv:value from W3C Data Quality Vocabulary would be semantically 
        appropriate but ontology not included in project. See 
        https://www.w3.org/TR/vocab-dqv/
```

---

## Verification Workflow

### Before Adding New Mappings

1. **Check if ontology file exists**:
   ```bash
   ls data/ontology/ | grep -i "<ontology-name>"
   ```

2. **Search for predicate in ontology**:
   ```bash
   grep -l "<predicate-name>" data/ontology/*
   ```

3. **Verify predicate definition**:
   ```bash
   grep -B2 -A5 "<predicate-name>" data/ontology/<file>
   ```

4. **If not found**: Use `hc:` prefix with appropriate documentation

### When Reviewing Existing Mappings

Run validation script:

```bash
# Find all slot_uri references
grep -r "slot_uri:" schemas/20251121/linkml/modules/slots/ | \
  grep -v "hc:" | \
  cut -d: -f3 | \
  sort -u

# Verify each prefix has a local file
for prefix in prov schema org skos dcterms foaf rico; do
  echo "Checking $prefix:"
  ls data/ontology/ | grep -i "$prefix" || echo "  NOT FOUND!"
done
```

---

## Ontology Addition Process

If a new ontology is genuinely needed:

1. **Download the ontology**:
   ```bash
   curl -L -o data/ontology/<name>.ttl "<url>" -H "Accept: text/turtle"
   ```

2. **Update ONTOLOGY_CATALOG.md**:
   ```bash
   # Add entry to data/ontology/ONTOLOGY_CATALOG.md
   ```

3. **Verify predicates exist**:
   ```bash
   grep "<predicate>" data/ontology/<name>.ttl
   ```

4. **Update LinkML prefixes** in schema files

---

## Examples

### CORRECT: Verified Mapping

```yaml
slots:
  retrieval_timestamp:
    slot_uri: prov:atTime  # Verified in data/ontology/prov-o.ttl
    range: datetime
```

### CORRECT: Domain-Specific with External Reference

```yaml
slots:
  confidence_score:
    slot_uri: hc:confidenceScore  # HC namespace (always valid)
    range: float
    close_mappings:
      - dqv:value  # External reference (documented, not required locally)
    annotations:
      ontology_note: >-
        Uses HC namespace as dqv: ontology not in local files.
        dqv:value would be semantically appropriate alternative.
```

### WRONG: Hallucinated Mapping

```yaml
slots:
  confidence_score:
    slot_uri: dqv:value  # INVALID - dqv: not in data/ontology/!
    range: float
```

### WRONG: Non-Existent Predicate

```yaml
slots:
  frame_rate:
    slot_uri: premis:hasFrameRate  # INVALID - predicate not in premis3.owl!
    range: float
```

---

## Consequences of Violation

1. **RDF serialization fails** - Invalid prefixes cause gen-owl errors
2. **Schema validation errors** - LinkML validates prefix declarations
3. **Broken interoperability** - External systems cannot resolve URIs
4. **Data quality issues** - Semantic web tooling cannot process data

---

## PREMIS Ontology Reference (premis3.owl)

**CRITICAL**: The PREMIS ontology is frequently hallucinated. ALL premis: references MUST be verified.

### Valid PREMIS Classes

```
Action, Agent, Bitstream, Copyright, Dependency, EnvironmentCharacteristic,
Event, File, Fixity, HardwareAgent, Identifier, Inhibitor, InstitutionalPolicy,
IntellectualEntity, License, Object, Organization, OutcomeStatus, Person,
PreservationPolicy, Representation, RightsBasis, RightsStatus, Rule, Signature,
SignatureEncoding, SignificantProperties, SoftwareAgent, Statute,
StorageLocation, StorageMedium
```

### Valid PREMIS Properties

```
act, allows, basis, characteristic, citation, compositionLevel, dependency,
determinationDate, documentation, encoding, endDate, fixity, governs,
identifier, inhibitedBy, inhibits, jurisdiction, key, medium, note,
originalName, outcome, outcomeNote, policy, prohibits, purpose, rationale,
relationship, restriction, rightsStatus, signature, size, startDate,
storedAt, terms, validationRules, version
```

### Known Hallucinated PREMIS Terms (DO NOT USE)

| Hallucinated Term | Correction |
|-------------------|------------|
| `premis:PreservationEvent` | Use `premis:Event` |
| `premis:RightsDeclaration` | Use `premis:RightsBasis` or `premis:RightsStatus` |
| `premis:hasRightsStatement` | Use `premis:rightsStatus` |
| `premis:hasRightsDeclaration` | Use `premis:rightsStatus` |
| `premis:hasRepresentation` | Use `premis:relationship` or `dcterms:hasFormat` |
| `premis:hasRelatedStatementInformation` | Use `premis:note` or `adms:status` |
| `premis:hasObjectCharacteristics` | Use `premis:characteristic` |
| `premis:rightsGranted` | Use `premis:RightsStatus` class with `premis:restriction` |
| `premis:rightsEndDate` | Use `premis:endDate` |
| `premis:linkingAgentIdentifier` | Use `premis:Agent` class |
| `premis:storageLocation` (lowercase) | Use `premis:storedAt` property or `premis:StorageLocation` class |
| `premis:hasFrameRate` | Does not exist - use `hc:frameRate` |
| `premis:environmentCharacteristic` (lowercase) | Use `premis:EnvironmentCharacteristic` (class) |

### PREMIS Verification Commands

```bash
# List all PREMIS classes
grep -E "owl:Class.*premis" data/ontology/premis3.owl | \
  sed 's/.*v3\///' | sed 's/".*//' | sort -u

# List all PREMIS properties
grep -E "ObjectProperty|DatatypeProperty" data/ontology/premis3.owl | \
  grep -oP 'v3/\K[^"]+' | sort -u

# Verify a specific term exists
grep -c "YourTermHere" data/ontology/premis3.owl
```

---

## See Also

- Rule 38: Slot Centralization and Semantic URI Requirements
- Rule 50: Ontology-to-LinkML Mapping Convention
- `/data/ontology/ONTOLOGY_CATALOG.md` - Available ontologies
- `.opencode/rules/slot-ontology-mapping-reference.md` - Mapping reference

---

## Version History

- **2025-01-13**: Added 7 more hallucinated PREMIS terms discovered during schema audit:
  - `premis:hasRightsStatement`, `premis:hasRightsDeclaration`, `premis:hasRepresentation`
  - `premis:hasRelatedStatementInformation`, `premis:rightsGranted`, `premis:rightsEndDate`
  - `premis:linkingAgentIdentifier`
- **2025-01-13**: Initial creation after discovering dqv:, adms:, qudt: references without local files