semantica/docs/reference/triplet_store.md

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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 full SPARQL query support. Use it when you need semantic web compatibility, OWL reasoning, SPARQL-based queries, or standards-compliant RDF serialization.

Exported Classes

Class	Role
TripletStore	Unified interface: add_triplet, get_triplets, delete_triplet, execute_query, bulk_load
QueryEngine	SPARQL 1.1 execution with query optimization and result streaming
BulkLoader	High-volume RDF loading with progress tracking and transaction batching
BlazegraphStore	Blazegraph REST API — Named Graphs, SPARQL 1.1 Update, GeoSPARQL
JenaStore	Apache Jena Fuseki — TDB2 backend, GeoSPARQL, SPARQL 1.1
RDF4JStore	Eclipse RDF4J — SailRepository, in-memory or native store

What You Get

Unified interface across Blazegraph, Apache Jena (Fuseki), and RDF4J — swap backends with one parameter. Zero-setup in-memory mode via `backend="memory"` for unit tests and small datasets — no server required. Full SELECT, CONSTRUCT, ASK, and UPDATE query support with pagination for large result sets. Apache Jena supports OWL and RDFS inference natively — subclass and property chain queries automatically resolved. Isolate triples by source, dataset, or time period using named graph management. Load and serialize to Turtle, JSON-LD, N-Triples, and RDF/XML with a single method call.

Quick Start

```python from semantica.triplet_store import TripletStore

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

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

# Bulk load a list of triplets
store.add_triplets_bulk(triplets)
```

```python results = store.sparql(""" PREFIX ex: SELECT ?person ?company WHERE { ?person ex:founded ?company . ?company ex:located_in ex:SiliconValley . } """)

for row in results:
    print(row["person"], row["company"])
```

```python store.export("output.ttl", format="turtle") store.export("output.nt", format="nt") store.export("output.xml", format="xml") ```

Backends

```python from semantica.triplet_store import TripletStore

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

Best for: Wikidata-style workloads, high triple counts, SPARQL 1.1 full support.

```python store = TripletStore( backend="jena", endpoint="http://localhost:3030/dataset/sparql", update_endpoint="http://localhost:3030/dataset/update" ) ```

Best for: General RDF, standard SPARQL, production deployments needing OWL inference.

**Enable OWL reasoning:**

```python
store = TripletStore(
    backend="jena",
    endpoint="http://localhost:3030/dataset/sparql",
    update_endpoint="http://localhost:3030/dataset/update",
    reasoner="OWL",        # "OWL" | "RDFS" | "OWL_MINI" | None
)

# Load an OWL ontology — subclass/property chain inferences are automatic
store.import_file("ontology.ttl", format="turtle")
store.add_triplets_bulk(data_triplets)

# Query using inferred relationships
results = store.sparql("""
    SELECT ?person WHERE {
        ?person a ex:Employee .       # inferred via subClassOf chain
    }
""")
```

```python store = TripletStore( backend="rdf4j", server_url="http://localhost:8080/rdf4j-server", repository_id="semantica" ) ```

Best for: Enterprise Java ecosystems, Eclipse Foundation deployments, plugin-based reasoning.

| Backend | License | OWL Reasoning | Hosted Option | Best For |
| ------- | ------- | ------------- | ------------- | -------- |
| Blazegraph | Open source | No | Self-hosted | Wikidata-style workloads, high triple count |
| Apache Jena | Apache 2.0 | Yes (OWL/RDFS) | Self-hosted | General RDF, OWL reasoning, standard SPARQL |
| RDF4J | Eclipse 1.0 | Via plugin | Self-hosted or cloud | Enterprise Java ecosystems |
| InMemory | Built-in | No | N/A | Unit tests, small graphs, no server required |

Namespace Prefix Management

Register custom prefixes to keep SPARQL queries readable:

from semantica.triplet_store import TripletStore
from semantica.ontology import NamespaceManager

ns = NamespaceManager(base_uri="http://example.org/")
ns.register("ex",     "http://example.org/")
ns.register("schema", "https://schema.org/")
ns.register("owl",    "http://www.w3.org/2002/07/owl#")

store = TripletStore(backend="jena", endpoint="...")

# Registered prefixes are automatically prepended to every SPARQL query
results = store.sparql("""
    SELECT ?company WHERE {
        ?person ex:works_for ?company ;
                schema:name  "Alice" .
    }
""")

TripletStore Methods

Method	Returns	Description
add_triplet(s, p, o, graph=None)	str	Add a single triplet, returns triplet ID
add_triplets_bulk(triplets)	List[str]	Batch add triplets with transaction support
get_triplets(graph=None)	List[dict]	Retrieve all triplets or from a named graph
delete_triplet(triplet_id)	bool	Delete a triplet by ID
sparql(query)	List[dict]	Execute SPARQL SELECT query
sparql_construct(query)	Graph	Execute SPARQL CONSTRUCT query
sparql_ask(query)	bool	Execute SPARQL ASK query
sparql_update(query)	None	Execute SPARQL UPDATE (INSERT/DELETE)
bulk_load(file, format)	None	Load RDF file (turtle, nt, xml)
export(path, format)	None	Export to turtle, nt, xml
list_graphs()	List[str]	List all named graphs
clear_graph(graph_uri)	None	Delete all triples from a named graph

SPARQL Queries

# SELECT — returns tabular results
results = store.sparql("""
    PREFIX ex: <http://example.org/>
    SELECT ?person ?company WHERE {
        ?person ex:founded ?company .
        ?company ex:located_in ex:SiliconValley .
    }
""")

# CONSTRUCT — returns a graph of matched triples
graph = store.sparql_construct("""
    PREFIX ex: <http://example.org/>
    CONSTRUCT {
        ?s ex:connected_to ?o
    } WHERE {
        ?s ex:founded ?company .
        ?company ex:has_investor ?o .
    }
""")

# ASK — returns True/False
exists = store.sparql_ask("""
    PREFIX ex: <http://example.org/>
    ASK { ex:apple_inc ex:founded_by ex:steve_jobs . }
""")

# UPDATE — insert or delete triples
store.sparql_update("""
    PREFIX ex: <http://example.org/>
    INSERT DATA {
        ex:apple_inc ex:listed_on ex:NASDAQ .
    }
""")

SPARQL Result Pagination

For large result sets, paginate with LIMIT and OFFSET:

page_size = 1000
offset    = 0

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

Named Graph Management

# Named graphs — store triples in isolated contexts
store.add_triplet(
    subject="http://example.org/a",
    predicate="http://example.org/p",
    obj="http://example.org/b",
    graph="http://example.org/graph1"
)

# Query a specific named graph
results = store.sparql("""
    SELECT ?s ?p ?o FROM <http://example.org/graph1> WHERE {
        ?s ?p ?o .
    }
""")

# List all named graphs
graphs = store.list_graphs()

# Clear a named graph
store.clear_graph("http://example.org/graph1")

Integration with Export Module

The Export module can write RDF that the triplet store then imports:

from semantica.export import RDFExporter
from semantica.triplet_store import TripletStore

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

# Load into triplet store
store = TripletStore(backend="jena", endpoint="http://localhost:3030/dataset/sparql")
store.import_file("output.ttl", format="turtle")

# Now query with SPARQL
results = store.sparql("SELECT * WHERE { ?s ?p ?o } LIMIT 10")

Tips and Common Pitfalls

**Use Apache Jena (Fuseki) for development and Blazegraph for production.** Jena runs with a single Docker command, supports OWL reasoning natively, and requires no licence. Switch to Blazegraph for high-throughput workloads by changing the `backend=` parameter — no other code changes needed. **Paginate large SPARQL result sets.** A `SELECT * WHERE { ?s ?p ?o }` against a million-triple store can return gigabytes of data. Always include `LIMIT` and `OFFSET` in exploratory queries, and iterate with `page_size` when you need full coverage. Unbounded queries against large stores will OOM or timeout. **Use named graphs to isolate sources.** `store.add_triplet(..., graph="http://example.org/source_A")` puts triples into a named graph. You can then query just that source, merge selectively, or clear it without touching other data — far safer than mixing all triples into the default graph. **Register namespace prefixes before querying.** `NamespacePrefixManager` lets you write `?s ex:name ?o` instead of `?s ?o`. Without prefixes, SPARQL queries against domain ontologies become unreadable and error-prone. **Enable OWL reasoning only when you need it.** `reasoner="OWL"` significantly increases query planning overhead. For simple triple lookups or SPARQL SELECT queries, leave reasoning off (`reasoner=None`) and enable it only for queries that depend on class hierarchies or property chains. **Export to Turtle before migrating backends.** If you need to move from Jena to Blazegraph (or any other store), `store.export("dump.ttl", format="turtle")` produces a portable file that any SPARQL store can import. Don't rely on backend-specific dump formats. Export knowledge graphs to RDF formats. Load OWL ontologies into a triplet store. SPARQL-based property chain inference. Property graph alternative for Cypher queries.