semantica/docs/reference/triplet_store.md

title, description, icon

title	description	icon
Triplet Store Module	Embedded and server-backed RDF storage with SPARQL queries and bulk loading.	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
OxigraphStore	Embedded SPARQL 1.1 store with in-memory and on-disk modes

What You Get

• TripletStore — Unified interface across embedded Oxigraph, Blazegraph, Apache Jena, and RDF4J: swap backends with one parameter.
• SPARQL — Full SPARQL SELECT, ASK, CONSTRUCT, and UPDATE query support via execute_query().
• Bulk Loading — add_triplets() batches writes with configurable batch size, retry logic, and progress tracking.
• SKOS Vocabulary — Built-in helpers: add_skos_concept() and get_skos_concepts() for controlled vocabulary management.
• Named Graphs — Oxigraph, Blazegraph, and RDF4J support named graph scoping via graph= on execute_query().
• Delta Computation — 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 "semantica[tripletstore-oxigraph]" ```

```python
# In-memory: no server process or files required
store = TripletStore(backend="oxigraph")

# Persistent: reopen the same directory to reuse the data
persistent_store = TripletStore(
    backend="oxigraph",
    path="./data/knowledge-graph",
)
```

**Best for:** local development, CI, desktop applications, and persistent
single-process workloads without external infrastructure.

```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.

<Warning>
  **`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.
</Warning>

```bash pip install requests ```

```python
store = TripletStore(
    backend="rdf4j",
    endpoint="http://localhost:8080/rdf4j-server",
    repository_id="semantica",   # selects the remote repository
)
```

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

| Backend | License | Named Graphs | Write via | Best For |
| :------- | :------- | :------------ | :--------- | :-------- |
| Oxigraph | Apache 2.0 / MIT | Yes | Embedded native API | Local, CI, on-disk |
| 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 |

**Use Oxigraph for zero-infrastructure development and local persistence.** Switch to a server-backed store for distributed production deployments by changing `backend=`.

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

**`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`.

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

**`execute_query()` returns `QueryResult`, not a list.** Iterate `result.bindings`, not `result` directly. Each binding is a dict mapping variable name → `{"value": ..., "type": ...}`.

SPARQL CONSTRUCT Templates

semantica.triplet_store.construct_templates provides parameterized SPARQL CONSTRUCT query templates: define a reusable query once, substitute typed parameters safely, and persist the resulting triples in one call. This is available for the Blazegraph backend only (see Backends above) — BlazegraphStore.execute_sparql() is the only backend with CONSTRUCT-aware RDF parsing.

from semantica.triplet_store.construct_templates import (
    ConstructTemplate,
    ParameterDescriptor,
    ConstructTemplateRegistry,
    render_construct_template,
    execute_construct_template,
)
from semantica.triplet_store import BlazegraphStore

# Define and register a template
template = ConstructTemplate(
    name="person_to_foaf",
    description="Maps a person record subject to a foaf:name triple",
    construct_query="""
        PREFIX foaf: <http://xmlns.com/foaf/0.1/>
        CONSTRUCT { {{subject}} foaf:name {{name}} ; foaf:age {{age}} }
        WHERE { {{subject}} a <http://ex.org/Person> }
    """,
    parameters=[
        ParameterDescriptor(name="subject", type="uri", required=True),
        ParameterDescriptor(name="name", type="literal", required=True),
        ParameterDescriptor(
            name="age", type="typed-literal", required=False, default=0,
            datatype="xsd:integer",
        ),
    ],
)

registry = ConstructTemplateRegistry()
registry.register(template)

# Render only: inspect the substituted SPARQL string, no network call
sparql = render_construct_template(
    registry.get("person_to_foaf"),
    params={"subject": "http://ex.org/p1", "name": "Alice", "age": 30},
)

# Render + execute + persist in one call
store = BlazegraphStore(endpoint="http://localhost:9999/blazegraph", namespace="kb")
triplets = execute_construct_template(
    template=registry.get("person_to_foaf"),
    params={"subject": "http://ex.org/p1", "name": "Alice", "age": 30},
    store_backend=store,
    target_graph="http://ex.org/graphs/people",
)
# triplets: List[Triplet], already persisted via store.add_triplets

Each ParameterDescriptor.type controls how its value is rendered: "uri" values are validated against an allowlist and wrapped in <...>, "literal" values are escaped and quoted, and "typed-literal" values require a datatype (e.g. "xsd:integer") and render unquoted for numeric/boolean XSD types. Placeholders use {{param}} rather than SPARQL's own ?param syntax so template placeholders are never confused with real SPARQL variables in the query body.

CONSTRUCT templates are Blazegraph-only. `execute_construct_template()` raises `ProcessingError` if `store_backend` does not implement both `execute_sparql()` and `add_triplets()`.

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

**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.

Named Graph Scoping

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

# Add a triplet to a named graph
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, graph="http://example.org/graph1")

# 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 query scoping is available for Oxigraph, Blazegraph, and RDF4J. The `graph=` query parameter is silently ignored for the Jena backend. **Use named graphs to isolate sources.** Pass `graph="http://example.org/source_A"` to writes and `execute_query()` to scope both storage and retrieval. Oxigraph, Blazegraph, and RDF4J support named graph query scoping.

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)

• Export — Export knowledge graphs to RDF formats.
• Ontology — Load OWL ontologies and store as RDF triples.
• Reasoning — SPARQL-based property chain inference.
• Graph Store — Property graph alternative for Cypher queries.