semantica/docs/reference/triplet_store.md

title, description, icon

title	description	icon
Triplet Store Module	RDF triple storage with SPARQL queries and bulk loading: Blazegraph, Apache Jena, and RDF4J.	table

semantica.triplet_store provides W3C-standard RDF storage with SPARQL 1.1 query support. Use it when you need semantic web compatibility, OWL-style reasoning, SPARQL-based queries, or standards-compliant RDF serialization.

Exported Classes

Class	Role
TripletStore	Unified interface: add_triplet, add_triplets, get_triplets, delete_triplet, execute_query
QueryEngine	SPARQL 1.1 execution with query optimization and result caching
BulkLoader	High-volume RDF loading with batching, retries, and progress tracking
BlazegraphStore	Blazegraph REST API: SPARQL 1.1 Update, namespace management
JenaStore	Apache Jena: rdflib-backed, SPARQL read support via remote endpoint
RDF4JStore	Eclipse RDF4J: REST API, transaction support

What You Get

Unified interface across Blazegraph, Apache Jena, and RDF4J: swap backends with one parameter. Full SPARQL SELECT, ASK, CONSTRUCT, and UPDATE query support via `execute_query()`. `add_triplets()` batches writes with configurable batch size, retry logic, and progress tracking. Built-in helpers: `add_skos_concept()` and `get_skos_concepts()` for controlled vocabulary management. Blazegraph and RDF4J support named graph scoping via `graph=` on `execute_query()`. `compute_delta(old_graph_uri, new_graph_uri)` returns added and removed triples between two named graph snapshots.

Getting Started

TripletStore wraps the backend of your choice. Construct a Triplet object (from semantica.semantic_extract.types) and call add_triplet():

from semantica.triplet_store import TripletStore
from semantica.semantic_extract.types import Triplet

store = TripletStore(
    backend="blazegraph",
    endpoint="http://localhost:9999/blazegraph/sparql"
)

# Create and store a single triplet
t = Triplet(
    subject="http://example.org/apple_inc",
    predicate="http://example.org/founded_by",
    object="http://example.org/steve_jobs",
)
store.add_triplet(t)

# Query with SPARQL: returns a QueryResult with a .bindings list
result = store.execute_query("""
    PREFIX ex: <http://example.org/>
    SELECT ?person ?company WHERE {
        ?person ex:founded ?company .
    }
""")

for row in result.bindings:
    person  = row.get("person",  {}).get("value")
    company = row.get("company", {}).get("value")
    print(person, company)

Quick Start

```python from semantica.triplet_store import TripletStore

store = TripletStore(
    backend="blazegraph",
    endpoint="http://localhost:9999/blazegraph/sparql"
)
```

```python from semantica.semantic_extract.types import Triplet

# Add a single triplet
store.add_triplet(Triplet(
    subject="http://example.org/apple_inc",
    predicate="http://example.org/founded_by",
    object="http://example.org/steve_jobs",
))

# Bulk-add a list of Triplet objects
store.add_triplets(triplets, batch_size=500)
```

```python # execute_query returns a QueryResult: iterate result.bindings result = store.execute_query(""" PREFIX ex: SELECT ?person ?company WHERE { ?person ex:founded ?company . ?company ex:located_in ex:SiliconValley . } """)

for row in result.bindings:
    print(row.get("person",  {}).get("value"))
    print(row.get("company", {}).get("value"))
```

```python # store(knowledge_graph, ontology) converts entities/relationships # to RDF triples and bulk-loads them in one call store.store(knowledge_graph=kg_dict, ontology=ontology_dict) ```

Backends

```bash pip install requests ```

```python
from semantica.triplet_store import TripletStore

store = TripletStore(
    backend="blazegraph",
    endpoint="http://localhost:9999/blazegraph/sparql",
    namespace="kb",      # default: "kb"
    timeout=30,          # request timeout in seconds
)
```

**Best for:** Wikidata-style workloads, high triple counts, named graph support, SPARQL 1.1 Update.

```bash pip install rdflib ```

```python
store = TripletStore(
    backend="jena",
    endpoint="http://localhost:3030/ds",   # SPARQL read endpoint for rdflib SPARQLStore
)
```

**Best for:** local development with rdflib, SPARQL read queries against a Fuseki endpoint.

**Note on inference:** `JenaStore` accepts `enable_inference=True` in config but OWL reasoning is a placeholder and does not produce inferred triples in the current implementation.

```bash pip install requests ```

```python
store = TripletStore(
    backend="rdf4j",
    endpoint="http://localhost:8080/rdf4j-server",
    repository_id="semantica",   # passed through **config
)
```

**Best for:** Eclipse Foundation deployments, transaction-based loading via REST API.

| Backend | License | Named Graphs | Write via | Best For |
| :------- | :------- | :------------ | :--------- | :-------- |
| Blazegraph | Open source | Yes | SPARQL Update REST | High triple count, SPARQL 1.1 |
| Apache Jena | Apache 2.0 | No (rdflib backend) | rdflib in-process | Local dev, read queries |
| RDF4J | Eclipse 1.0 | Yes | REST API N-Triples | Enterprise Java, transactions |

Triplet Object

All store operations use the Triplet dataclass from semantica.semantic_extract.types:

from semantica.semantic_extract.types import Triplet

t = Triplet(
    subject="http://example.org/apple_inc",     # required: full URI string
    predicate="http://example.org/founded_by",  # required: full URI string
    object="http://example.org/steve_jobs",     # required: URI or literal string
    confidence=0.95,                            # optional: float 0.0–1.0, default 1.0
    metadata={"source": "wikipedia"},           # optional: dict
)

Field	Type	Default	Description
subject	str	required	Subject URI
predicate	str	required	Predicate URI
object	str	required	Object URI or literal
confidence	float	1.0	Confidence score (0–1)
metadata	dict	{}	Arbitrary metadata

TripletStore Methods

Method	Returns	Description
add_triplet(triplet)	dict	Add a single Triplet object
add_triplets(triplets, batch_size)	dict	Bulk-add a list of Triplet objects; returns {"success", "total", "processed", "failed", "batches"}
get_triplets(subject, predicate, object)	List[Triplet]	Retrieve triplets matching subject/predicate/object filters
delete_triplet(triplet)	dict	Delete a Triplet from the store
update_triplet(old_triplet, new_triplet)	dict	Atomic delete + add
execute_query(query, parameters, graph, graphs)	QueryResult	Execute a SPARQL query: returns QueryResult with .bindings, .variables, .execution_time
store(knowledge_graph, ontology)	dict	Convert a KG + ontology dict to RDF triples and bulk-load them
add_skos_concept(concept_uri, scheme_uri, pref_label, ...)	dict	Add a SKOS concept with optional alt labels, broader/narrower/related
get_skos_concepts(scheme_uri)	List[dict]	Retrieve all SKOS concepts, optionally filtered by scheme URI
compute_delta(old_graph_uri, new_graph_uri)	dict	Return {"added_triples", "removed_triples", "added_count", "removed_count"} between two named graph snapshots
get_stats()	dict	Get backend statistics

SPARQL Queries

execute_query() is the single entry point for all SPARQL operations. It returns a QueryResult: access results via .bindings:

from semantica.triplet_store import TripletStore

store = TripletStore(backend="blazegraph", endpoint="http://localhost:9999/blazegraph/sparql")

# SELECT: iterate result.bindings
result = store.execute_query("""
    PREFIX ex: <http://example.org/>
    SELECT ?person ?company WHERE {
        ?person ex:founded ?company .
    }
""")

for row in result.bindings:
    print(row.get("person",  {}).get("value"))
    print(row.get("company", {}).get("value"))

# ASK, CONSTRUCT, UPDATE: same method, different SPARQL form
result = store.execute_query("""
    PREFIX ex: <http://example.org/>
    ASK { ex:apple_inc ex:founded_by ex:steve_jobs . }
""")
print(result.bindings)   # ASK returns boolean result in bindings

# SPARQL UPDATE (INSERT/DELETE)
store.execute_query("""
    PREFIX ex: <http://example.org/>
    INSERT DATA {
        ex:apple_inc ex:listed_on ex:NASDAQ .
    }
""")

QueryResult fields

Field	Type	Description
bindings	List[dict]	Each dict maps variable name → {"value": ..., "type": ...}
variables	List[str]	SPARQL result variable names
execution_time	float	Seconds elapsed
metadata	dict	Query, graph scope, cache hit flag

SPARQL Result Pagination

For large result sets, paginate with LIMIT and OFFSET:

page_size = 1000
offset    = 0

while True:
    result = store.execute_query(f"""
        SELECT ?s ?p ?o WHERE {{
            ?s ?p ?o .
        }}
        ORDER BY ?s
        LIMIT {page_size} OFFSET {offset}
    """)
    if not result.bindings:
        break
    process_batch(result.bindings)
    offset += page_size

Named Graph Scoping

Blazegraph and RDF4J support named graphs. Scope execute_query() to a named graph with the graph= parameter:

# Add a triplet: named graph stored in metadata or backend-specific API
from semantica.semantic_extract.types import Triplet

t = Triplet(
    subject="http://example.org/a",
    predicate="http://example.org/p",
    object="http://example.org/b",
)
store.add_triplet(t)   # named graph targeting requires backend-specific API

# Query a named graph via FROM clause in SPARQL
result = store.execute_query("""
    SELECT ?s ?p ?o WHERE {
        ?s ?p ?o .
    }
""", graph="http://example.org/graph1")   # injects FROM <graph> before WHERE

# Or scope inline using FROM in the query string
result = store.execute_query("""
    SELECT ?s ?p ?o FROM <http://example.org/graph1> WHERE {
        ?s ?p ?o .
    }
""")

Named graph support is only available for Blazegraph and RDF4J backends. The `graph=` parameter is silently ignored for the Jena backend.

Bulk Loading

add_triplets() batches writes via the internal BulkLoader. Access store.bulk_loader to configure it:

from semantica.triplet_store import TripletStore
from semantica.semantic_extract.types import Triplet

store = TripletStore(backend="blazegraph", endpoint="http://localhost:9999/blazegraph/sparql")

# Default: batch_size=1000, max_retries=3
result = store.add_triplets(triplets)
# Returns: {"success": True, "total": N, "processed": N, "failed": 0, "batches": B}

# Custom batch size for this call
result = store.add_triplets(triplets, batch_size=500)

# Validate before loading
validation = store.bulk_loader.validate_before_load(triplets)
if not validation["valid"]:
    print(validation["errors"])

BulkLoader can also be used directly with a progress_callback:

from semantica.triplet_store import BulkLoader

loader = BulkLoader(batch_size=2000, max_retries=5, retry_delay=2.0)

def on_progress(p):
    print(f"{p.progress_percentage:.1f}%  ({p.loaded_triplets}/{p.total_triplets})")

progress = loader.load_triplets(triplets, store._store_backend, progress_callback=on_progress)
print(f"Loaded {progress.loaded_triplets} in {progress.elapsed_time:.2f}s")

Storing a Knowledge Graph

store(knowledge_graph, ontology) converts a KG+ontology dict structure to RDF and bulk-loads everything in one call:

kg = {
    "entities": [
        {"id": "apple_inc",  "type": "Organization", "properties": {"name": "Apple Inc."}},
        {"id": "steve_jobs", "type": "Person",        "properties": {"name": "Steve Jobs"}},
    ],
    "relationships": [
        {"source": "steve_jobs", "target": "apple_inc", "type": "founded"}
    ],
}
ontology = {
    "uri": "https://example.org/ontology/",
    "classes": [
        {"name": "Organization"},
        {"name": "Person"},
    ],
    "properties": [
        {"name": "founded", "type": "object", "domain": ["Person"], "range": ["Organization"]},
    ],
}

result = store.store(knowledge_graph=kg, ontology=ontology)
# Returns add_triplets result dict

SKOS Vocabulary Management

store.add_skos_concept(
    concept_uri="http://example.org/skos/MachineLearning",
    scheme_uri="http://example.org/skos/AIScheme",
    pref_label="Machine Learning",
    alt_labels=["ML", "Statistical Learning"],
    broader=["http://example.org/skos/AI"],
    definition="A field of artificial intelligence...",
)

# Retrieve all concepts in a scheme
concepts = store.get_skos_concepts(scheme_uri="http://example.org/skos/AIScheme")
for c in concepts:
    print(c["uri"], c["pref_label"], c["alt_labels"])

Delta Computation

# Compare two named graph snapshots and return added/removed triples
delta = store.compute_delta(
    old_graph_uri="http://example.org/graph/v1",
    new_graph_uri="http://example.org/graph/v2",
)

print(f"Added:   {delta['added_count']} triples")
print(f"Removed: {delta['removed_count']} triples")

for t in delta["added_triples"]:
    print(f"+  {t.subject}  {t.predicate}  {t.object}")
for t in delta["removed_triples"]:
    print(f"-  {t.subject}  {t.predicate}  {t.object}")

Integration with Export Module

The Export module writes RDF that the triplet store can then receive via add_triplets():

from semantica.export import RDFExporter
from semantica.triplet_store import TripletStore
from semantica.semantic_extract.types import Triplet

# Export KG to Turtle
exporter = RDFExporter()
exporter.export_to_file(kg, "output.ttl", format="turtle")

# Parse the file and load triplets into the store
# (TripletStore does not have a built-in import_file() method —
#  parse with rdflib and convert to Triplet objects)
import rdflib
g = rdflib.Graph()
g.parse("output.ttl", format="turtle")

store = TripletStore(backend="jena", endpoint="http://localhost:3030/ds")
triplets = [
    Triplet(subject=str(s), predicate=str(p), object=str(o))
    for s, p, o in g
]
store.add_triplets(triplets)

# Query with SPARQL
result = store.execute_query("SELECT * WHERE { ?s ?p ?o } LIMIT 10")
for row in result.bindings:
    print(row)

Tips and Common Pitfalls

**Use Apache Jena for development, Blazegraph for production.** Jena initializes with rdflib in-memory: no server required for local testing. Switch to Blazegraph for high-throughput persistent workloads by changing `backend=`. **`execute_query()` returns `QueryResult`, not a list.** Iterate `result.bindings`, not `result` directly. Each binding is a dict mapping variable name → `{"value": ..., "type": ...}`. **`add_triplet()` takes a `Triplet` object, not keyword arguments.** Use `Triplet(subject=..., predicate=..., object=...)` from `semantica.semantic_extract.types` and pass the object: not `subject=`, `predicate=`, `obj=` to `add_triplet`. **Paginate large SPARQL result sets.** A `SELECT * WHERE { ?s ?p ?o }` against a large store returns all triples. Always include `LIMIT` and `OFFSET` in exploratory queries. `QueryEngine` adds `LIMIT 1000` automatically unless you specify one. **Use named graphs to isolate sources.** Pass `graph="http://example.org/source_A"` to `execute_query()` to scope a query to a specific named graph. Blazegraph and RDF4J support named graphs; Jena (rdflib backend) does not. **`backend="jena"` OWL inference is a placeholder.** `enable_inference=True` is accepted but the inference call returns 0 inferred triples. For production OWL reasoning, use Jena Fuseki directly with its built-in reasoner configuration. Export knowledge graphs to RDF formats. Load OWL ontologies and store as RDF triples. SPARQL-based property chain inference. Property graph alternative for Cypher queries.