Feature/improve ontology extract (#576)

* Tech spec to change ontology extraction * Ontology extract refactoring
2026-04-25 00:16:23 +02:00 · 2025-12-03 13:36:10 +00:00 · 2025-12-03 13:36:10 +00:00 · b957004db9
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+# Ontology Knowledge Extraction - Phase 2 Refactor
+
+**Status**: Draft
+**Author**: Analysis Session 2025-12-03
+**Related**: `ontology.md`, `ontorag.md`
+
+## Overview
+
+This document identifies inconsistencies in the current ontology-based knowledge extraction system and proposes a refactor to improve LLM performance and reduce information loss.
+
+## Current Implementation
+
+### How It Works Now
+
+1. **Ontology Loading** (`ontology_loader.py`)
+   - Loads ontology JSON with keys like `"fo/Recipe"`, `"fo/Food"`, `"fo/produces"`
+   - Class IDs include namespace prefix in the key itself
+   - Example from `food.ontology`:
+     ```json
+     "classes": {
+       "fo/Recipe": {
+         "uri": "http://purl.org/ontology/fo/Recipe",
+         "rdfs:comment": "A Recipe is a combination..."
+       }
+     }
+     ```
+
+2. **Prompt Construction** (`extract.py:299-307`, `ontology-prompt.md`)
+   - Template receives `classes`, `object_properties`, `datatype_properties` dicts
+   - Template iterates: `{% for class_id, class_def in classes.items() %}`
+   - LLM sees: `**fo/Recipe**: A Recipe is a combination...`
+   - Example output format shows:
+     ```json
+     {"subject": "recipe:cornish-pasty", "predicate": "rdf:type", "object": "Recipe"}
+     {"subject": "recipe:cornish-pasty", "predicate": "has_ingredient", "object": "ingredient:flour"}
+     ```
+
+3. **Response Parsing** (`extract.py:382-428`)
+   - Expects JSON array: `[{"subject": "...", "predicate": "...", "object": "..."}]`
+   - Validates against ontology subset
+   - Expands URIs via `expand_uri()` (extract.py:473-521)
+
+4. **URI Expansion** (`extract.py:473-521`)
+   - Checks if value is in `ontology_subset.classes` dict
+   - If found, extracts URI from class definition
+   - If not found, constructs URI: `f"https://trustgraph.ai/ontology/{ontology_id}#{value}"`
+
+### Data Flow Example
+
+**Ontology JSON → Loader → Prompt:**
+```
+"fo/Recipe" → classes["fo/Recipe"] → LLM sees "**fo/Recipe**"
+```
+
+**LLM → Parser → Output:**
+```
+"Recipe" → not in classes["fo/Recipe"] → constructs URI → LOSES original URI
+"fo/Recipe" → found in classes → uses original URI → PRESERVES URI
+```
+
+## Problems Identified
+
+### 1. **Inconsistent Examples in Prompt**
+
+**Issue**: The prompt template shows class IDs with prefixes (`fo/Recipe`) but the example output uses unprefixed class names (`Recipe`).
+
+**Location**: `ontology-prompt.md:5-52`
+
+```markdown
+## Ontology Classes:
+- **fo/Recipe**: A Recipe is...
+
+## Example Output:
+{"subject": "recipe:cornish-pasty", "predicate": "rdf:type", "object": "Recipe"}
+```
+
+**Impact**: LLM receives conflicting signals about what format to use.
+
+### 2. **Information Loss in URI Expansion**
+
+**Issue**: When LLM returns unprefixed class names following the example, `expand_uri()` can't find them in the ontology dict and constructs fallback URIs, losing the original proper URIs.
+
+**Location**: `extract.py:494-500`
+
+```python
+if value in ontology_subset.classes:  # Looks for "Recipe"
+    class_def = ontology_subset.classes[value]  # But key is "fo/Recipe"
+    if isinstance(class_def, dict) and 'uri' in class_def:
+        return class_def['uri']  # Never reached!
+return f"https://trustgraph.ai/ontology/{ontology_id}#{value}"  # Fallback
+```
+
+**Impact**:
+- Original URI: `http://purl.org/ontology/fo/Recipe`
+- Constructed URI: `https://trustgraph.ai/ontology/food#Recipe`
+- Semantic meaning lost, breaks interoperability
+
+### 3. **Ambiguous Entity Instance Format**
+
+**Issue**: No clear guidance on entity instance URI format.
+
+**Examples in prompt**:
+- `"recipe:cornish-pasty"` (namespace-like prefix)
+- `"ingredient:flour"` (different prefix)
+
+**Actual behavior** (extract.py:517-520):
+```python
+# Treat as entity instance - construct unique URI
+normalized = value.replace(" ", "-").lower()
+return f"https://trustgraph.ai/{ontology_id}/{normalized}"
+```
+
+**Impact**: LLM must guess prefixing convention with no ontology context.
+
+### 4. **No Namespace Prefix Guidance**
+
+**Issue**: The ontology JSON contains namespace definitions (line 10-25 in food.ontology):
+```json
+"namespaces": {
+  "fo": "http://purl.org/ontology/fo/",
+  "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+  ...
+}
+```
+
+But these are never surfaced to the LLM. The LLM doesn't know:
+- What "fo" means
+- What prefix to use for entities
+- Which namespace applies to which elements
+
+### 5. **Labels Not Used in Prompt**
+
+**Issue**: Every class has `rdfs:label` fields (e.g., `{"value": "Recipe", "lang": "en-gb"}`), but the prompt template doesn't use them.
+
+**Current**: Shows only `class_id` and `comment`
+```jinja
+- **{{class_id}}**{% if class_def.comment %}: {{class_def.comment}}{% endif %}
+```
+
+**Available but unused**:
+```python
+"rdfs:label": [{"value": "Recipe", "lang": "en-gb"}]
+```
+
+**Impact**: Could provide human-readable names alongside technical IDs.
+
+## Proposed Solutions
+
+### Option A: Normalize to Unprefixed IDs
+
+**Approach**: Strip prefixes from class IDs before showing to LLM.
+
+**Changes**:
+1. Modify `build_extraction_variables()` to transform keys:
+   ```python
+   classes_for_prompt = {
+       k.split('/')[-1]: v  # "fo/Recipe" → "Recipe"
+       for k, v in ontology_subset.classes.items()
+   }
+   ```
+
+2. Update prompt example to match (already uses unprefixed names)
+
+3. Modify `expand_uri()` to handle both formats:
+   ```python
+   # Try exact match first
+   if value in ontology_subset.classes:
+       return ontology_subset.classes[value]['uri']
+
+   # Try with prefix
+   for prefix in ['fo/', 'rdf:', 'rdfs:']:
+       prefixed = f"{prefix}{value}"
+       if prefixed in ontology_subset.classes:
+           return ontology_subset.classes[prefixed]['uri']
+   ```
+
+**Pros**:
+- Cleaner, more human-readable
+- Matches existing prompt examples
+- LLMs work better with simpler tokens
+
+**Cons**:
+- Class name collisions if multiple ontologies have same class name
+- Loses namespace information
+- Requires fallback logic for lookups
+
+### Option B: Use Full Prefixed IDs Consistently
+
+**Approach**: Update examples to use prefixed IDs matching what's shown in the class list.
+
+**Changes**:
+1. Update prompt example (ontology-prompt.md:46-52):
+   ```json
+   [
+     {"subject": "recipe:cornish-pasty", "predicate": "rdf:type", "object": "fo/Recipe"},
+     {"subject": "recipe:cornish-pasty", "predicate": "rdfs:label", "object": "Cornish Pasty"},
+     {"subject": "recipe:cornish-pasty", "predicate": "fo/produces", "object": "food:cornish-pasty"},
+     {"subject": "food:cornish-pasty", "predicate": "rdf:type", "object": "fo/Food"}
+   ]
+   ```
+
+2. Add namespace explanation to prompt:
+   ```markdown
+   ## Namespace Prefixes:
+   - **fo/**: Food Ontology (http://purl.org/ontology/fo/)
+   - **rdf:**: RDF Schema
+   - **rdfs:**: RDF Schema
+
+   Use these prefixes exactly as shown when referencing classes and properties.
+   ```
+
+3. Keep `expand_uri()` as-is (works correctly when matches found)
+
+**Pros**:
+- Input = Output consistency
+- No information loss
+- Preserves namespace semantics
+- Works with multiple ontologies
+
+**Cons**:
+- More verbose tokens for LLM
+- Requires LLM to track prefixes
+
+### Option C: Hybrid - Show Both Label and ID
+
+**Approach**: Enhance prompt to show both human-readable labels and technical IDs.
+
+**Changes**:
+1. Update prompt template:
+   ```jinja
+   {% for class_id, class_def in classes.items() %}
+   - **{{class_id}}** (label: "{{class_def.labels[0].value if class_def.labels else class_id}}"){% if class_def.comment %}: {{class_def.comment}}{% endif %}
+   {% endfor %}
+   ```
+
+   Example output:
+   ```markdown
+   - **fo/Recipe** (label: "Recipe"): A Recipe is a combination...
+   ```
+
+2. Update instructions:
+   ```markdown
+   When referencing classes:
+   - Use the full prefixed ID (e.g., "fo/Recipe") in JSON output
+   - The label (e.g., "Recipe") is for human understanding only
+   ```
+
+**Pros**:
+- Clearest for LLM
+- Preserves all information
+- Explicit about what to use
+
+**Cons**:
+- Longer prompt
+- More complex template
+
+## Implemented Approach
+
+**Simplified Entity-Relationship-Attribute Format** - completely replaces the old triple-based format.
+
+The new approach was chosen because:
+
+1. **No Information Loss**: Original URIs preserved correctly
+2. **Simpler Logic**: No transformation needed, direct dict lookups work
+3. **Namespace Safety**: Handles multiple ontologies without collisions
+4. **Semantic Correctness**: Maintains RDF/OWL semantics
+
+## Implementation Complete
+
+### What Was Built:
+
+1. **New Prompt Template** (`prompts/ontology-extract-v2.txt`)
+   - ✅ Clear sections: Entity Types, Relationships, Attributes
+   - ✅ Example using full type identifiers (`fo/Recipe`, `fo/has_ingredient`)
+   - ✅ Instructions to use exact identifiers from schema
+   - ✅ New JSON format with entities/relationships/attributes arrays
+
+2. **Entity Normalization** (`entity_normalizer.py`)
+   - ✅ `normalize_entity_name()` - Converts names to URI-safe format
+   - ✅ `normalize_type_identifier()` - Handles slashes in types (`fo/Recipe` → `fo-recipe`)
+   - ✅ `build_entity_uri()` - Creates unique URIs using (name, type) tuple
+   - ✅ `EntityRegistry` - Tracks entities for deduplication
+
+3. **JSON Parser** (`simplified_parser.py`)
+   - ✅ Parses new format: `{entities: [...], relationships: [...], attributes: [...]}`
+   - ✅ Supports kebab-case and snake_case field names
+   - ✅ Returns structured dataclasses
+   - ✅ Graceful error handling with logging
+
+4. **Triple Converter** (`triple_converter.py`)
+   - ✅ `convert_entity()` - Generates type + label triples automatically
+   - ✅ `convert_relationship()` - Connects entity URIs via properties
+   - ✅ `convert_attribute()` - Adds literal values
+   - ✅ Looks up full URIs from ontology definitions
+
+5. **Updated Main Processor** (`extract.py`)
+   - ✅ Removed old triple-based extraction code
+   - ✅ Added `extract_with_simplified_format()` method
+   - ✅ Now exclusively uses new simplified format
+   - ✅ Calls prompt with `extract-with-ontologies-v2` ID
+
+## Test Cases
+
+### Test 1: URI Preservation
+```python
+# Given ontology class
+classes = {"fo/Recipe": {"uri": "http://purl.org/ontology/fo/Recipe", ...}}
+
+# When LLM returns
+llm_output = {"subject": "x", "predicate": "rdf:type", "object": "fo/Recipe"}
+
+# Then expanded URI should be
+assert expanded == "http://purl.org/ontology/fo/Recipe"
+# Not: "https://trustgraph.ai/ontology/food#Recipe"
+```
+
+### Test 2: Multi-Ontology Collision
+```python
+# Given two ontologies
+ont1 = {"fo/Recipe": {...}}
+ont2 = {"cooking/Recipe": {...}}
+
+# LLM should use full prefix to disambiguate
+llm_output = {"object": "fo/Recipe"}  # Not just "Recipe"
+```
+
+### Test 3: Entity Instance Format
+```python
+# Given prompt with food ontology
+# LLM should create instances like
+{"subject": "recipe:cornish-pasty"}  # Namespace-style
+{"subject": "food:beef"}              # Consistent prefix
+```
+
+## Open Questions
+
+1. **Should entity instances use namespace prefixes?**
+   - Current: `"recipe:cornish-pasty"` (arbitrary)
+   - Alternative: Use ontology prefix `"fo:cornish-pasty"`?
+   - Alternative: No prefix, expand in URI `"cornish-pasty"` → full URI?
+
+2. **How to handle domain/range in prompt?**
+   - Currently shows: `(Recipe → Food)`
+   - Should it be: `(fo/Recipe → fo/Food)`?
+
+3. **Should we validate domain/range constraints?**
+   - TODO comment at extract.py:470
+   - Would catch more errors but more complex
+
+4. **What about inverse properties and equivalences?**
+   - Ontology has `owl:inverseOf`, `owl:equivalentClass`
+   - Not currently used in extraction
+   - Should they be?
+
+## Success Metrics
+
+- ✅ Zero URI information loss (100% preservation of original URIs)
+- ✅ LLM output format matches input format
+- ✅ No ambiguous examples in prompt
+- ✅ Tests pass with multiple ontologies
+- ✅ Improved extraction quality (measured by valid triple %)
+
+## Alternative Approach: Simplified Extraction Format
+
+### Philosophy
+
+Instead of asking the LLM to understand RDF/OWL semantics, ask it to do what it's good at: **find entities and relationships in text**.
+
+Let the code handle URI construction, RDF conversion, and semantic web formalities.
+
+### Example: Entity Classification
+
+**Input Text:**
+```
+Cornish pasty is a traditional British pastry filled with meat and vegetables.
+```
+
+**Ontology Schema (shown to LLM):**
+```markdown
+## Entity Types:
+- Recipe: A recipe is a combination of ingredients and a method
+- Food: A food is something that can be eaten
+- Ingredient: An ingredient combines a quantity and a food
+```
+
+**What LLM Returns (Simple JSON):**
+```json
+{
+  "entities": [
+    {
+      "entity": "Cornish pasty",
+      "type": "Recipe"
+    }
+  ]
+}
+```
+
+**What Code Produces (RDF Triples):**
+```python
+# 1. Normalize entity name + type to ID (type prevents collisions)
+entity_id = "recipe-cornish-pasty"  # normalize("Cornish pasty", "Recipe")
+entity_uri = "https://trustgraph.ai/food/recipe-cornish-pasty"
+
+# Note: Same name, different type = different URI
+# "Cornish pasty" (Recipe) → recipe-cornish-pasty
+# "Cornish pasty" (Food) → food-cornish-pasty
+
+# 2. Generate triples
+triples = [
+    # Type triple
+    Triple(
+        s=Value(value=entity_uri, is_uri=True),
+        p=Value(value="http://www.w3.org/1999/02/22-rdf-syntax-ns#type", is_uri=True),
+        o=Value(value="http://purl.org/ontology/fo/Recipe", is_uri=True)
+    ),
+    # Label triple (automatic)
+    Triple(
+        s=Value(value=entity_uri, is_uri=True),
+        p=Value(value="http://www.w3.org/2000/01/rdf-schema#label", is_uri=True),
+        o=Value(value="Cornish pasty", is_uri=False)
+    )
+]
+```
+
+### Benefits
+
+1. **LLM doesn't need to:**
+   - Understand URI syntax
+   - Invent identifier prefixes (`recipe:`, `ingredient:`)
+   - Know about `rdf:type` or `rdfs:label`
+   - Construct semantic web identifiers
+
+2. **LLM just needs to:**
+   - Find entities in text
+   - Map them to ontology classes
+   - Extract relationships and attributes
+
+3. **Code handles:**
+   - URI normalization and construction
+   - RDF triple generation
+   - Automatic label assignment
+   - Namespace management
+
+### Why This Works Better
+
+- **Simpler prompt** = less confusion = fewer errors
+- **Consistent IDs** = code controls normalization rules
+- **Auto-generated labels** = no missing rdfs:label triples
+- **LLM focuses on extraction** = what it's actually good at
+
+### Example: Entity Relationships
+
+**Input Text:**
+```
+Cornish pasty is a traditional British pastry filled with beef and potatoes.
+```
+
+**Ontology Schema (shown to LLM):**
+```markdown
+## Entity Types:
+- Recipe: A recipe is a combination of ingredients and a method
+- Food: A food is something that can be eaten
+- Ingredient: An ingredient combines a quantity and a food
+
+## Relationships:
+- has_ingredient: Relates a recipe to an ingredient it uses (Recipe → Ingredient)
+- food: Relates an ingredient to the food that is required (Ingredient → Food)
+```
+
+**What LLM Returns (Simple JSON):**
+```json
+{
+  "entities": [
+    {
+      "entity": "Cornish pasty",
+      "type": "Recipe"
+    },
+    {
+      "entity": "beef",
+      "type": "Food"
+    },
+    {
+      "entity": "potatoes",
+      "type": "Food"
+    }
+  ],
+  "relationships": [
+    {
+      "subject": "Cornish pasty",
+      "subject-type": "Recipe",
+      "relation": "has_ingredient",
+      "object": "beef",
+      "object-type": "Food"
+    },
+    {
+      "subject": "Cornish pasty",
+      "subject-type": "Recipe",
+      "relation": "has_ingredient",
+      "object": "potatoes",
+      "object-type": "Food"
+    }
+  ]
+}
+```
+
+**What Code Produces (RDF Triples):**
+```python
+# Normalize entity names to URIs
+cornish_pasty_uri = "https://trustgraph.ai/food/cornish-pasty"
+beef_uri = "https://trustgraph.ai/food/beef"
+potatoes_uri = "https://trustgraph.ai/food/potatoes"
+
+# Look up relation URI from ontology
+has_ingredient_uri = "http://purl.org/ontology/fo/ingredients"  # from fo/has_ingredient
+
+triples = [
+    # Entity type triples (as before)
+    Triple(s=cornish_pasty_uri, p=rdf_type, o="http://purl.org/ontology/fo/Recipe"),
+    Triple(s=cornish_pasty_uri, p=rdfs_label, o="Cornish pasty"),
+
+    Triple(s=beef_uri, p=rdf_type, o="http://purl.org/ontology/fo/Food"),
+    Triple(s=beef_uri, p=rdfs_label, o="beef"),
+
+    Triple(s=potatoes_uri, p=rdf_type, o="http://purl.org/ontology/fo/Food"),
+    Triple(s=potatoes_uri, p=rdfs_label, o="potatoes"),
+
+    # Relationship triples
+    Triple(
+        s=Value(value=cornish_pasty_uri, is_uri=True),
+        p=Value(value=has_ingredient_uri, is_uri=True),
+        o=Value(value=beef_uri, is_uri=True)
+    ),
+    Triple(
+        s=Value(value=cornish_pasty_uri, is_uri=True),
+        p=Value(value=has_ingredient_uri, is_uri=True),
+        o=Value(value=potatoes_uri, is_uri=True)
+    )
+]
+```
+
+**Key Points:**
+- LLM returns natural language entity names: `"Cornish pasty"`, `"beef"`, `"potatoes"`
+- LLM includes types to disambiguate: `subject-type`, `object-type`
+- LLM uses relation name from schema: `"has_ingredient"`
+- Code derives consistent IDs using (name, type): `("Cornish pasty", "Recipe")` → `recipe-cornish-pasty`
+- Code looks up relation URI from ontology: `fo/has_ingredient` → full URI
+- Same (name, type) tuple always gets same URI (deduplication)
+
+### Example: Entity Name Disambiguation
+
+**Problem:** Same name can refer to different entity types.
+
+**Real-world case:**
+```
+"Cornish pasty" can be:
+- A Recipe (instructions for making it)
+- A Food (the dish itself)
+```
+
+**How It's Handled:**
+
+LLM returns both as separate entities:
+```json
+{
+  "entities": [
+    {"entity": "Cornish pasty", "type": "Recipe"},
+    {"entity": "Cornish pasty", "type": "Food"}
+  ],
+  "relationships": [
+    {
+      "subject": "Cornish pasty",
+      "subject-type": "Recipe",
+      "relation": "produces",
+      "object": "Cornish pasty",
+      "object-type": "Food"
+    }
+  ]
+}
+```
+
+**Code Resolution:**
+```python
+# Different types → different URIs
+recipe_uri = normalize("Cornish pasty", "Recipe")
+# → "https://trustgraph.ai/food/recipe-cornish-pasty"
+
+food_uri = normalize("Cornish pasty", "Food")
+# → "https://trustgraph.ai/food/food-cornish-pasty"
+
+# Relationship connects them correctly
+triple = Triple(
+    s=recipe_uri,  # The Recipe
+    p="http://purl.org/ontology/fo/produces",
+    o=food_uri     # The Food
+)
+```
+
+**Why This Works:**
+- Type is included in ALL references (entities, relationships, attributes)
+- Code uses `(name, type)` tuple as lookup key
+- No ambiguity, no collisions
+
+### Example: Entity Attributes
+
+**Input Text:**
+```
+This Cornish pasty recipe serves 4-6 people and takes 45 minutes to prepare.
+```
+
+**Ontology Schema (shown to LLM):**
+```markdown
+## Entity Types:
+- Recipe: A recipe is a combination of ingredients and a method
+
+## Attributes:
+- serves: Indicates what the recipe is intended to serve (Recipe → text)
+- preparation_time: Time needed to prepare the recipe (Recipe → text)
+```
+
+**What LLM Returns (Simple JSON):**
+```json
+{
+  "entities": [
+    {
+      "entity": "Cornish pasty recipe",
+      "type": "Recipe"
+    }
+  ],
+  "attributes": [
+    {
+      "entity": "Cornish pasty recipe",
+      "entity-type": "Recipe",
+      "attribute": "serves",
+      "value": "4-6 people"
+    },
+    {
+      "entity": "Cornish pasty recipe",
+      "entity-type": "Recipe",
+      "attribute": "preparation_time",
+      "value": "45 minutes"
+    }
+  ]
+}
+```
+
+**What Code Produces (RDF Triples):**
+```python
+# Normalize entity name to URI
+recipe_uri = "https://trustgraph.ai/food/cornish-pasty-recipe"
+
+# Look up attribute URIs from ontology
+serves_uri = "http://purl.org/ontology/fo/serves"  # from fo/serves
+prep_time_uri = "http://purl.org/ontology/fo/preparation_time"  # from fo/preparation_time
+
+triples = [
+    # Entity type triple
+    Triple(
+        s=Value(value=recipe_uri, is_uri=True),
+        p=Value(value=rdf_type, is_uri=True),
+        o=Value(value="http://purl.org/ontology/fo/Recipe", is_uri=True)
+    ),
+
+    # Label triple (automatic)
+    Triple(
+        s=Value(value=recipe_uri, is_uri=True),
+        p=Value(value=rdfs_label, is_uri=True),
+        o=Value(value="Cornish pasty recipe", is_uri=False)
+    ),
+
+    # Attribute triples (objects are literals, not URIs)
+    Triple(
+        s=Value(value=recipe_uri, is_uri=True),
+        p=Value(value=serves_uri, is_uri=True),
+        o=Value(value="4-6 people", is_uri=False)  # Literal value!
+    ),
+    Triple(
+        s=Value(value=recipe_uri, is_uri=True),
+        p=Value(value=prep_time_uri, is_uri=True),
+        o=Value(value="45 minutes", is_uri=False)  # Literal value!
+    )
+]
+```
+
+**Key Points:**
+- LLM extracts literal values: `"4-6 people"`, `"45 minutes"`
+- LLM includes entity type for disambiguation: `entity-type`
+- LLM uses attribute name from schema: `"serves"`, `"preparation_time"`
+- Code looks up attribute URI from ontology datatype properties
+- **Object is literal** (`is_uri=False`), not a URI reference
+- Values stay as natural text, no normalization needed
+
+**Difference from Relationships:**
+- Relationships: both subject and object are entities (URIs)
+- Attributes: subject is entity (URI), object is literal value (string/number)
+
+### Complete Example: Entities + Relationships + Attributes
+
+**Input Text:**
+```
+Cornish pasty is a savory pastry filled with beef and potatoes.
+This recipe serves 4 people.
+```
+
+**What LLM Returns:**
+```json
+{
+  "entities": [
+    {
+      "entity": "Cornish pasty",
+      "type": "Recipe"
+    },
+    {
+      "entity": "beef",
+      "type": "Food"
+    },
+    {
+      "entity": "potatoes",
+      "type": "Food"
+    }
+  ],
+  "relationships": [
+    {
+      "subject": "Cornish pasty",
+      "subject-type": "Recipe",
+      "relation": "has_ingredient",
+      "object": "beef",
+      "object-type": "Food"
+    },
+    {
+      "subject": "Cornish pasty",
+      "subject-type": "Recipe",
+      "relation": "has_ingredient",
+      "object": "potatoes",
+      "object-type": "Food"
+    }
+  ],
+  "attributes": [
+    {
+      "entity": "Cornish pasty",
+      "entity-type": "Recipe",
+      "attribute": "serves",
+      "value": "4 people"
+    }
+  ]
+}
+```
+
+**Result:** 11 RDF triples generated:
+- 3 entity type triples (rdf:type)
+- 3 entity label triples (rdfs:label) - automatic
+- 2 relationship triples (has_ingredient)
+- 1 attribute triple (serves)
+
+All from simple, natural language extractions by the LLM!
+
+## References
+
+- Current implementation: `trustgraph-flow/trustgraph/extract/kg/ontology/extract.py`
+- Prompt template: `ontology-prompt.md`
+- Test cases: `tests/unit/test_extract/test_ontology/`
+- Example ontology: `e2e/test-data/food.ontology`
--- a/ontology-prompt.md
+++ b/ontology-prompt.md
@ -0,0 +1,54 @@
+You are a knowledge extraction expert. Extract structured triples from text using ONLY the provided ontology elements.
+
+## Ontology Classes:
+
+{% for class_id, class_def in classes.items() %}
+- **{{class_id}}**{% if class_def.subclass_of %} (subclass of {{class_def.subclass_of}}){% endif %}{% if class_def.comment %}: {{class_def.comment}}{% endif %}
+{% endfor %}
+
+## Object Properties (connect entities):
+
+{% for prop_id, prop_def in object_properties.items() %}
+- **{{prop_id}}**{% if prop_def.domain and prop_def.range %} ({{prop_def.domain}} → {{prop_def.range}}){% endif %}{% if prop_def.comment %}: {{prop_def.comment}}{% endif %}
+{% endfor %}
+
+## Datatype Properties (entity attributes):
+
+{% for prop_id, prop_def in datatype_properties.items() %}
+- **{{prop_id}}**{% if prop_def.domain and prop_def.range %} ({{prop_def.domain}} → {{prop_def.range}}){% endif %}{% if prop_def.comment %}: {{prop_def.comment}}{% endif %}
+{% endfor %}
+
+## Text to Analyze:
+
+{{text}}
+
+## Extraction Rules:
+
+1. Only use classes defined above for entity types
+2. Only use properties defined above for relationships and attributes
+3. Respect domain and range constraints where specified
+4. For class instances, use `rdf:type` as the predicate
+5. Include `rdfs:label` for new entities to provide human-readable names
+6. Extract all relevant triples that can be inferred from the text
+7. Use entity URIs or meaningful identifiers as subjects/objects
+
+## Output Format:
+
+Return ONLY a valid JSON array (no markdown, no code blocks) containing objects with these fields:
+- "subject": the subject entity (URI or identifier)
+- "predicate": the property (from ontology or rdf:type/rdfs:label)
+- "object": the object entity or literal value
+
+Important: Return raw JSON only, with no markdown formatting, no code blocks, and no backticks.
+
+## Example Output:
+
+[
+  {"subject": "recipe:cornish-pasty", "predicate": "rdf:type", "object": "Recipe"},
+  {"subject": "recipe:cornish-pasty", "predicate": "rdfs:label", "object": "Cornish Pasty"},
+  {"subject": "recipe:cornish-pasty", "predicate": "has_ingredient", "object": "ingredient:flour"},
+  {"subject": "ingredient:flour", "predicate": "rdf:type", "object": "Ingredient"},
+  {"subject": "ingredient:flour", "predicate": "rdfs:label", "object": "plain flour"}
+]
+
+Now extract triples from the text above.
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/entity_normalizer.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/entity_normalizer.py
@ -0,0 +1,164 @@
+"""
+Entity URI normalization for ontology-based knowledge extraction.
+
+Converts entity names and types into consistent, collision-free URIs.
+"""
+
+import re
+from typing import Tuple
+
+
+def normalize_entity_name(entity_name: str) -> str:
+    """Normalize entity name to URI-safe identifier.
+
+    Args:
+        entity_name: Natural language entity name (e.g., "Cornish pasty")
+
+    Returns:
+        Normalized identifier (e.g., "cornish-pasty")
+    """
+    # Convert to lowercase
+    normalized = entity_name.lower()
+
+    # Replace spaces and underscores with hyphens
+    normalized = re.sub(r'[\s_]+', '-', normalized)
+
+    # Remove any characters that aren't alphanumeric, hyphens, or periods
+    normalized = re.sub(r'[^a-z0-9\-.]', '', normalized)
+
+    # Remove leading/trailing hyphens
+    normalized = normalized.strip('-')
+
+    # Collapse multiple hyphens
+    normalized = re.sub(r'-+', '-', normalized)
+
+    return normalized
+
+
+def normalize_type_identifier(type_id: str) -> str:
+    """Normalize ontology type identifier to URI-safe format.
+
+    Handles prefixed types like "fo/Recipe" by converting to "fo-recipe".
+
+    Args:
+        type_id: Ontology type identifier (e.g., "fo/Recipe", "Food")
+
+    Returns:
+        Normalized type identifier (e.g., "fo-recipe", "food")
+    """
+    # Convert to lowercase
+    normalized = type_id.lower()
+
+    # Replace slashes, colons, and spaces with hyphens
+    normalized = re.sub(r'[/:.\s_]+', '-', normalized)
+
+    # Remove any remaining non-alphanumeric characters except hyphens
+    normalized = re.sub(r'[^a-z0-9\-]', '', normalized)
+
+    # Remove leading/trailing hyphens
+    normalized = normalized.strip('-')
+
+    # Collapse multiple hyphens
+    normalized = re.sub(r'-+', '-', normalized)
+
+    return normalized
+
+
+def build_entity_uri(entity_name: str, entity_type: str, ontology_id: str,
+                    base_uri: str = "https://trustgraph.ai") -> str:
+    """Build a unique URI for an entity based on its name and type.
+
+    The type is included in the URI to prevent collisions when the same
+    name refers to different entity types (e.g., "Cornish pasty" as both
+    Recipe and Food).
+
+    Args:
+        entity_name: Natural language entity name (e.g., "Cornish pasty")
+        entity_type: Ontology type (e.g., "fo/Recipe")
+        ontology_id: Ontology identifier (e.g., "food")
+        base_uri: Base URI for entity URIs (default: "https://trustgraph.ai")
+
+    Returns:
+        Full entity URI (e.g., "https://trustgraph.ai/food/fo-recipe-cornish-pasty")
+
+    Examples:
+        >>> build_entity_uri("Cornish pasty", "fo/Recipe", "food")
+        'https://trustgraph.ai/food/fo-recipe-cornish-pasty'
+
+        >>> build_entity_uri("Cornish pasty", "fo/Food", "food")
+        'https://trustgraph.ai/food/fo-food-cornish-pasty'
+
+        >>> build_entity_uri("beef", "fo/Food", "food")
+        'https://trustgraph.ai/food/fo-food-beef'
+    """
+    type_part = normalize_type_identifier(entity_type)
+    name_part = normalize_entity_name(entity_name)
+
+    # Combine type and name to ensure uniqueness
+    entity_id = f"{type_part}-{name_part}"
+
+    # Build full URI
+    return f"{base_uri}/{ontology_id}/{entity_id}"
+
+
+class EntityRegistry:
+    """Registry to track entity name/type tuples and their assigned URIs.
+
+    Ensures that the same (entity_name, entity_type) tuple always maps
+    to the same URI, enabling deduplication across the extraction process.
+    """
+
+    def __init__(self, ontology_id: str, base_uri: str = "https://trustgraph.ai"):
+        """Initialize the entity registry.
+
+        Args:
+            ontology_id: Ontology identifier (e.g., "food")
+            base_uri: Base URI for entity URIs
+        """
+        self.ontology_id = ontology_id
+        self.base_uri = base_uri
+        self._registry = {}  # (entity_name, entity_type) -> uri
+
+    def get_or_create_uri(self, entity_name: str, entity_type: str) -> str:
+        """Get existing URI or create new one for entity.
+
+        Args:
+            entity_name: Natural language entity name
+            entity_type: Ontology type identifier
+
+        Returns:
+            URI for this entity (same URI for same name/type tuple)
+        """
+        key = (entity_name, entity_type)
+
+        if key not in self._registry:
+            uri = build_entity_uri(
+                entity_name,
+                entity_type,
+                self.ontology_id,
+                self.base_uri
+            )
+            self._registry[key] = uri
+
+        return self._registry[key]
+
+    def lookup(self, entity_name: str, entity_type: str) -> str:
+        """Look up URI for entity (returns None if not registered).
+
+        Args:
+            entity_name: Natural language entity name
+            entity_type: Ontology type identifier
+
+        Returns:
+            URI for this entity, or None if not found
+        """
+        key = (entity_name, entity_type)
+        return self._registry.get(key)
+
+    def clear(self):
+        """Clear all registered entities."""
+        self._registry.clear()
+
+    def size(self) -> int:
+        """Get number of registered entities."""
+        return len(self._registry)
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/extract.py
@ -20,6 +20,8 @@ from .ontology_embedder import OntologyEmbedder
 from .vector_store import InMemoryVectorStore
 from .text_processor import TextProcessor
 from .ontology_selector import OntologySelector, OntologySubset
+from .simplified_parser import parse_extraction_response
+from .triple_converter import TripleConverter

 logger = logging.getLogger(__name__)

@ -298,25 +300,10 @@ class Processor(FlowProcessor):
            # Build extraction prompt variables
            prompt_variables = self.build_extraction_variables(chunk, ontology_subset)

-            # Call prompt service for extraction
-            try:
-                # Use prompt() method with extract-with-ontologies prompt ID
-                triples_response = await flow("prompt-request").prompt(
-                    id="extract-with-ontologies",
-                    variables=prompt_variables
+            # Extract using simplified entity-relationship-attribute format
+            triples = await self.extract_with_simplified_format(
+                flow, chunk, ontology_subset, prompt_variables
            )
-                logger.debug(f"Extraction response: {triples_response}")
-
-                if not isinstance(triples_response, list):
-                    logger.error("Expected list of triples from prompt service")
-                    triples_response = []
-
-            except Exception as e:
-                logger.error(f"Prompt service error: {e}", exc_info=True)
-                triples_response = []
-
-            # Parse and validate triples
-            triples = self.parse_and_validate_triples(triples_response, ontology_subset)

            # Add metadata triples
            for t in v.metadata.metadata:
@ -362,6 +349,55 @@ class Processor(FlowProcessor):
                []
            )

+    async def extract_with_simplified_format(
+        self,
+        flow,
+        chunk: str,
+        ontology_subset: OntologySubset,
+        prompt_variables: Dict[str, Any]
+    ) -> List[Triple]:
+        """Extract triples using simplified entity-relationship-attribute format.
+
+        Args:
+            flow: Flow object for accessing services
+            chunk: Text chunk to extract from
+            ontology_subset: Selected ontology subset
+            prompt_variables: Variables for prompt template
+
+        Returns:
+            List of Triple objects
+        """
+        try:
+            # Call prompt service with simplified format prompt
+            extraction_response = await flow("prompt-request").prompt(
+                id="extract-with-ontologies",
+                variables=prompt_variables
+            )
+            logger.debug(f"Simplified extraction response: {extraction_response}")
+
+            # Parse response into structured format
+            extraction_result = parse_extraction_response(extraction_response)
+
+            if not extraction_result:
+                logger.warning("Failed to parse extraction response")
+                return []
+
+            logger.info(f"Parsed {len(extraction_result.entities)} entities, "
+                       f"{len(extraction_result.relationships)} relationships, "
+                       f"{len(extraction_result.attributes)} attributes")
+
+            # Convert to RDF triples
+            converter = TripleConverter(ontology_subset, ontology_subset.ontology_id)
+            triples = converter.convert_all(extraction_result)
+
+            logger.info(f"Generated {len(triples)} RDF triples from simplified extraction")
+
+            return triples
+
+        except Exception as e:
+            logger.error(f"Simplified extraction error: {e}", exc_info=True)
+            return []
+
    def build_extraction_variables(self, chunk: str, ontology_subset: OntologySubset) -> Dict[str, Any]:
        """Build variables for ontology-based extraction prompt template.

--- a/trustgraph-flow/trustgraph/extract/kg/ontology/simplified_parser.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/simplified_parser.py
@ -0,0 +1,234 @@
+"""
+Parser for simplified ontology extraction JSON format.
+
+Parses the new entity-relationship-attribute format from LLM responses.
+"""
+
+import json
+import logging
+from typing import List, Dict, Any, Optional
+from dataclasses import dataclass
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class Entity:
+    """Represents an extracted entity."""
+    entity: str
+    type: str
+
+
+@dataclass
+class Relationship:
+    """Represents an extracted relationship."""
+    subject: str
+    subject_type: str
+    relation: str
+    object: str
+    object_type: str
+
+
+@dataclass
+class Attribute:
+    """Represents an extracted attribute."""
+    entity: str
+    entity_type: str
+    attribute: str
+    value: str
+
+
+@dataclass
+class ExtractionResult:
+    """Complete extraction result."""
+    entities: List[Entity]
+    relationships: List[Relationship]
+    attributes: List[Attribute]
+
+
+def parse_extraction_response(response: Any) -> Optional[ExtractionResult]:
+    """Parse LLM extraction response into structured format.
+
+    Args:
+        response: LLM response (string JSON or already parsed dict)
+
+    Returns:
+        ExtractionResult with parsed entities/relationships/attributes,
+        or None if parsing fails
+    """
+    # Handle string response (parse JSON)
+    if isinstance(response, str):
+        try:
+            data = json.loads(response)
+        except json.JSONDecodeError as e:
+            logger.error(f"Failed to parse JSON response: {e}")
+            logger.debug(f"Response was: {response[:500]}")
+            return None
+    elif isinstance(response, dict):
+        data = response
+    else:
+        logger.error(f"Unexpected response type: {type(response)}")
+        return None
+
+    # Validate structure
+    if not isinstance(data, dict):
+        logger.error(f"Expected dict, got {type(data)}")
+        return None
+
+    # Parse entities
+    entities = []
+    entities_data = data.get('entities', [])
+    if not isinstance(entities_data, list):
+        logger.warning(f"'entities' is not a list: {type(entities_data)}")
+        entities_data = []
+
+    for entity_data in entities_data:
+        try:
+            entity = parse_entity(entity_data)
+            if entity:
+                entities.append(entity)
+        except Exception as e:
+            logger.warning(f"Failed to parse entity {entity_data}: {e}")
+
+    # Parse relationships
+    relationships = []
+    relationships_data = data.get('relationships', [])
+    if not isinstance(relationships_data, list):
+        logger.warning(f"'relationships' is not a list: {type(relationships_data)}")
+        relationships_data = []
+
+    for rel_data in relationships_data:
+        try:
+            relationship = parse_relationship(rel_data)
+            if relationship:
+                relationships.append(relationship)
+        except Exception as e:
+            logger.warning(f"Failed to parse relationship {rel_data}: {e}")
+
+    # Parse attributes
+    attributes = []
+    attributes_data = data.get('attributes', [])
+    if not isinstance(attributes_data, list):
+        logger.warning(f"'attributes' is not a list: {type(attributes_data)}")
+        attributes_data = []
+
+    for attr_data in attributes_data:
+        try:
+            attribute = parse_attribute(attr_data)
+            if attribute:
+                attributes.append(attribute)
+        except Exception as e:
+            logger.warning(f"Failed to parse attribute {attr_data}: {e}")
+
+    return ExtractionResult(
+        entities=entities,
+        relationships=relationships,
+        attributes=attributes
+    )
+
+
+def parse_entity(data: Dict[str, Any]) -> Optional[Entity]:
+    """Parse entity from dict.
+
+    Supports both kebab-case and snake_case field names for compatibility.
+
+    Args:
+        data: Entity dict with 'entity' and 'type' fields
+
+    Returns:
+        Entity object or None if invalid
+    """
+    if not isinstance(data, dict):
+        logger.warning(f"Entity data is not a dict: {type(data)}")
+        return None
+
+    entity = data.get('entity')
+    entity_type = data.get('type')
+
+    if not entity or not entity_type:
+        logger.warning(f"Missing required fields in entity: {data}")
+        return None
+
+    if not isinstance(entity, str) or not isinstance(entity_type, str):
+        logger.warning(f"Entity fields must be strings: {data}")
+        return None
+
+    return Entity(entity=entity, type=entity_type)
+
+
+def parse_relationship(data: Dict[str, Any]) -> Optional[Relationship]:
+    """Parse relationship from dict.
+
+    Supports both kebab-case and snake_case field names for compatibility.
+
+    Args:
+        data: Relationship dict with subject, subject-type, relation, object, object-type
+
+    Returns:
+        Relationship object or None if invalid
+    """
+    if not isinstance(data, dict):
+        logger.warning(f"Relationship data is not a dict: {type(data)}")
+        return None
+
+    subject = data.get('subject')
+    subject_type = data.get('subject-type') or data.get('subject_type')
+    relation = data.get('relation')
+    obj = data.get('object')
+    object_type = data.get('object-type') or data.get('object_type')
+
+    if not all([subject, subject_type, relation, obj, object_type]):
+        logger.warning(f"Missing required fields in relationship: {data}")
+        return None
+
+    if not all(isinstance(v, str) for v in [subject, subject_type, relation, obj, object_type]):
+        logger.warning(f"Relationship fields must be strings: {data}")
+        return None
+
+    return Relationship(
+        subject=subject,
+        subject_type=subject_type,
+        relation=relation,
+        object=obj,
+        object_type=object_type
+    )
+
+
+def parse_attribute(data: Dict[str, Any]) -> Optional[Attribute]:
+    """Parse attribute from dict.
+
+    Supports both kebab-case and snake_case field names for compatibility.
+
+    Args:
+        data: Attribute dict with entity, entity-type, attribute, value
+
+    Returns:
+        Attribute object or None if invalid
+    """
+    if not isinstance(data, dict):
+        logger.warning(f"Attribute data is not a dict: {type(data)}")
+        return None
+
+    entity = data.get('entity')
+    entity_type = data.get('entity-type') or data.get('entity_type')
+    attribute = data.get('attribute')
+    value = data.get('value')
+
+    if not all([entity, entity_type, attribute, value is not None]):
+        logger.warning(f"Missing required fields in attribute: {data}")
+        return None
+
+    if not all(isinstance(v, str) for v in [entity, entity_type, attribute]):
+        logger.warning(f"Attribute fields must be strings: {data}")
+        return None
+
+    # Value can be string, number, bool - convert to string
+    if not isinstance(value, str):
+        value = str(value)
+
+    return Attribute(
+        entity=entity,
+        entity_type=entity_type,
+        attribute=attribute,
+        value=value
+    )
--- a/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py
+++ b/trustgraph-flow/trustgraph/extract/kg/ontology/triple_converter.py
@ -0,0 +1,228 @@
+"""
+Converts simplified extraction format to RDF triples.
+
+Transforms entities, relationships, and attributes into proper RDF triples
+with full URIs and correct is_uri flags.
+"""
+
+import logging
+from typing import List, Optional
+
+from .... schema import Triple, Value
+from .... rdf import RDF_TYPE, RDF_LABEL
+
+from .simplified_parser import Entity, Relationship, Attribute, ExtractionResult
+from .entity_normalizer import EntityRegistry
+from .ontology_selector import OntologySubset
+
+logger = logging.getLogger(__name__)
+
+
+class TripleConverter:
+    """Converts extraction results to RDF triples."""
+
+    def __init__(self, ontology_subset: OntologySubset, ontology_id: str):
+        """Initialize converter.
+
+        Args:
+            ontology_subset: Ontology subset with classes and properties
+            ontology_id: Ontology identifier for URI generation
+        """
+        self.ontology_subset = ontology_subset
+        self.ontology_id = ontology_id
+        self.entity_registry = EntityRegistry(ontology_id)
+
+    def convert_all(self, extraction: ExtractionResult) -> List[Triple]:
+        """Convert complete extraction result to RDF triples.
+
+        Args:
+            extraction: Parsed extraction with entities/relationships/attributes
+
+        Returns:
+            List of RDF Triple objects
+        """
+        triples = []
+
+        # Convert entities (generates type + label triples)
+        for entity in extraction.entities:
+            entity_triples = self.convert_entity(entity)
+            triples.extend(entity_triples)
+
+        # Convert relationships
+        for relationship in extraction.relationships:
+            rel_triple = self.convert_relationship(relationship)
+            if rel_triple:
+                triples.append(rel_triple)
+
+        # Convert attributes
+        for attribute in extraction.attributes:
+            attr_triple = self.convert_attribute(attribute)
+            if attr_triple:
+                triples.append(attr_triple)
+
+        return triples
+
+    def convert_entity(self, entity: Entity) -> List[Triple]:
+        """Convert entity to RDF triples (type + label).
+
+        Args:
+            entity: Entity object with name and type
+
+        Returns:
+            List containing type triple and label triple
+        """
+        triples = []
+
+        # Get or create URI for this entity
+        entity_uri = self.entity_registry.get_or_create_uri(
+            entity.entity,
+            entity.type
+        )
+
+        # Look up class URI from ontology
+        class_uri = self._get_class_uri(entity.type)
+        if not class_uri:
+            logger.warning(f"Unknown entity type '{entity.type}', skipping entity '{entity.entity}'")
+            return triples
+
+        # Generate type triple: entity rdf:type ClassURI
+        type_triple = Triple(
+            s=Value(value=entity_uri, is_uri=True),
+            p=Value(value=RDF_TYPE, is_uri=True),
+            o=Value(value=class_uri, is_uri=True)
+        )
+        triples.append(type_triple)
+
+        # Generate label triple: entity rdfs:label "entity name"
+        label_triple = Triple(
+            s=Value(value=entity_uri, is_uri=True),
+            p=Value(value=RDF_LABEL, is_uri=True),
+            o=Value(value=entity.entity, is_uri=False)  # Literal!
+        )
+        triples.append(label_triple)
+
+        return triples
+
+    def convert_relationship(self, relationship: Relationship) -> Optional[Triple]:
+        """Convert relationship to RDF triple.
+
+        Args:
+            relationship: Relationship with subject/object entities and relation
+
+        Returns:
+            Triple connecting two entity URIs via property URI, or None if invalid
+        """
+        # Get URIs for subject and object entities
+        subject_uri = self.entity_registry.get_or_create_uri(
+            relationship.subject,
+            relationship.subject_type
+        )
+
+        object_uri = self.entity_registry.get_or_create_uri(
+            relationship.object,
+            relationship.object_type
+        )
+
+        # Look up property URI from ontology
+        property_uri = self._get_object_property_uri(relationship.relation)
+        if not property_uri:
+            logger.warning(f"Unknown relationship '{relationship.relation}', skipping")
+            return None
+
+        # Generate triple: subject property object
+        return Triple(
+            s=Value(value=subject_uri, is_uri=True),
+            p=Value(value=property_uri, is_uri=True),
+            o=Value(value=object_uri, is_uri=True)
+        )
+
+    def convert_attribute(self, attribute: Attribute) -> Optional[Triple]:
+        """Convert attribute to RDF triple.
+
+        Args:
+            attribute: Attribute with entity, attribute name, and literal value
+
+        Returns:
+            Triple with entity URI, property URI, and literal value, or None if invalid
+        """
+        # Get URI for entity
+        entity_uri = self.entity_registry.get_or_create_uri(
+            attribute.entity,
+            attribute.entity_type
+        )
+
+        # Look up property URI from ontology
+        property_uri = self._get_datatype_property_uri(attribute.attribute)
+        if not property_uri:
+            logger.warning(f"Unknown attribute '{attribute.attribute}', skipping")
+            return None
+
+        # Generate triple: entity property "literal value"
+        return Triple(
+            s=Value(value=entity_uri, is_uri=True),
+            p=Value(value=property_uri, is_uri=True),
+            o=Value(value=attribute.value, is_uri=False)  # Literal!
+        )
+
+    def _get_class_uri(self, class_id: str) -> Optional[str]:
+        """Get full URI for ontology class.
+
+        Args:
+            class_id: Class identifier (e.g., "fo/Recipe")
+
+        Returns:
+            Full class URI or None if not found
+        """
+        if class_id not in self.ontology_subset.classes:
+            return None
+
+        class_def = self.ontology_subset.classes[class_id]
+
+        # Extract URI from class definition
+        if isinstance(class_def, dict) and 'uri' in class_def:
+            return class_def['uri']
+
+        # Fallback: construct URI
+        return f"https://trustgraph.ai/ontology/{self.ontology_id}#{class_id}"
+
+    def _get_object_property_uri(self, property_id: str) -> Optional[str]:
+        """Get full URI for object property.
+
+        Args:
+            property_id: Property identifier (e.g., "fo/has_ingredient")
+
+        Returns:
+            Full property URI or None if not found
+        """
+        if property_id not in self.ontology_subset.object_properties:
+            return None
+
+        prop_def = self.ontology_subset.object_properties[property_id]
+
+        # Extract URI from property definition
+        if isinstance(prop_def, dict) and 'uri' in prop_def:
+            return prop_def['uri']
+
+        # Fallback: construct URI
+        return f"https://trustgraph.ai/ontology/{self.ontology_id}#{property_id}"
+
+    def _get_datatype_property_uri(self, property_id: str) -> Optional[str]:
+        """Get full URI for datatype property.
+
+        Args:
+            property_id: Property identifier (e.g., "fo/serves")
+
+        Returns:
+            Full property URI or None if not found
+        """
+        if property_id not in self.ontology_subset.datatype_properties:
+            return None
+
+        prop_def = self.ontology_subset.datatype_properties[property_id]
+
+        # Extract URI from property definition
+        if isinstance(prop_def, dict) and 'uri' in prop_def:
+            return prop_def['uri']
+
+        # Fallback: construct URI
+        return f"https://trustgraph.ai/ontology/{self.ontology_id}#{property_id}"