Add SPARQL CONSTRUCT query templates (Blazegraph-only)

Implements #322: ConstructTemplate/ParameterDescriptor/ConstructTemplateRegistry
with injection-safe {{param}} rendering, Blazegraph CONSTRUCT-aware execute_sparql
extension, execute_construct_template (render->execute->parse->persist), and a
construct_template pipeline step. RDF4J/Jena support deferred to a follow-up issue.

Closes #322

docs/reference/pipeline.md

@@ -495,6 +495,40 @@ result   = engine.execute_pipeline(
   Delta detection uses SHA-256 checksums on source content. Only sources whose checksum differs from `base_version_id` are passed to downstream steps. For pipelines that run hourly or daily against a growing corpus, delta mode eliminates redundant re-embedding and re-extraction.
 </Note>
 
+## SPARQL CONSTRUCT Template Steps
+
+Use the `"construct_template"` step type to render and execute a [SPARQL CONSTRUCT template](triplet_store#sparql-construct-templates) as part of a pipeline. `store_backend` and `construct_template_registry` are execution-time resources, not step config — pass them to `execute_pipeline()`, the same way `delta_mode` steps receive `version_manager` and `triplet_store`:
+
+```python
+from semantica.pipeline import PipelineBuilder, ExecutionEngine
+from semantica.triplet_store.construct_templates import construct_template_step_handler
+
+builder = PipelineBuilder()
+builder.add_step(
+    "apply_person_template",
+    "construct_template",
+    handler=construct_template_step_handler,
+    template_name="person_to_foaf",
+    params={"subject": "http://ex.org/p1", "name": "Alice", "age": 30},
+    target_graph="http://ex.org/graphs/people",
+)
+pipeline = builder.build("person_pipeline")
+
+engine = ExecutionEngine()
+result = engine.execute_pipeline(
+    pipeline,
+    data=None,
+    store_backend=store,                   # required: a BlazegraphStore instance
+    construct_template_registry=registry,  # required: holds the registered template
+)
+
+triplets = result.output   # List[Triplet], already persisted via store.add_triplets
+```
+
+<Note>
+  `construct_template` steps raise `ProcessingError` if `store_backend` or `construct_template_registry` is missing from `execute_pipeline()`'s options, and `ValidationError` if `template_name` isn't registered.
+</Note>
+
 ## Schemas
 
 <AccordionGroup>

docs/reference/triplet_store.md

@@ -277,6 +277,65 @@ store.execute_query("""
   **`execute_query()` returns `QueryResult`, not a list.** Iterate `result.bindings`, not `result` directly. Each binding is a dict mapping variable name → `{"value": ..., "type": ...}`.
 </Warning>
 
+## 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](#backends) above) — `BlazegraphStore.execute_sparql()` is the only backend with CONSTRUCT-aware RDF parsing.
+
+```python
+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.
+
+<Note>
+  CONSTRUCT templates are Blazegraph-only. `execute_construct_template()` raises `ProcessingError` if `store_backend` does not implement both `execute_sparql()` and `add_triplets()`.
+</Note>
+
 ## SPARQL Result Pagination
 
 For large result sets, paginate with LIMIT and OFFSET:

semantica/triplet_store/blazegraph_store.py

@@ -32,11 +32,15 @@ from typing import Any, Dict, List, Optional
 from urllib.parse import urljoin, urlparse
 
 import requests
+from rdflib import Graph
 
 from ..semantic_extract.triplet_extractor import Triplet
 from ..utils.exceptions import ProcessingError, ValidationError
 from ..utils.logging import get_logger
 from ..utils.progress_tracker import get_progress_tracker
+from . import sparql_escaping
+
+_CONSTRUCT_QUERY_RE = re.compile(r"\bCONSTRUCT\b", re.IGNORECASE)
 
 
 class BlazegraphStore:
@@ -111,16 +115,42 @@ class BlazegraphStore:
         """Get SPARQL Update endpoint URL."""
         return urljoin(self.endpoint, f"/blazegraph/namespace/{self.namespace}/sparql")
 
+    def _is_construct_query(self, query: str) -> bool:
+        """
+        Detect whether `query` is a SPARQL CONSTRUCT query.
+
+        This is a dispatch helper local to BlazegraphStore, distinct from
+        QueryEngine._validate_query (which already treats CONSTRUCT as one of
+        its valid_keywords and therefore requires no change — CONSTRUCT
+        queries already pass validation today). This helper only decides
+        which HTTP Accept header and response parser execute_sparql uses; it
+        does not gate query validity.
+        """
+        return _CONSTRUCT_QUERY_RE.search(query) is not None
+
     def execute_sparql(self, query: str, **options) -> Dict[str, Any]:
         """
         Execute SPARQL query.
 
         Args:
             query: SPARQL query string
-            **options: Additional options
+            **options: Additional options:
+                - result_format: Optional[Literal["bindings", "construct"]].
+                  If omitted, auto-detected via _is_construct_query(query).
 
         Returns:
-            Query results
+            Query results. For non-CONSTRUCT queries (or when result_format
+            resolves to "bindings"), the existing shape is unchanged:
+                {"success": bool, "bindings": [...], "variables": [...], "metadata": {...}}
+            For CONSTRUCT queries (or result_format="construct"), the shape is:
+                {"success": bool, "bindings": [], "variables": [], "triples": [...],
+                 "metadata": {...}}
+            where "triples" is a list of (subject, predicate, object) string
+            3-tuples parsed from the Turtle response via rdflib.
+
+        Raises:
+            ProcessingError: if not connected, the HTTP request fails, or (for
+                CONSTRUCT queries) the response body fails to parse as Turtle.
         """
         tracking_id = self.progress_tracker.start_tracking(
             module="triplet_store",
@@ -137,6 +167,62 @@ class BlazegraphStore:
 
             sparql_endpoint = self._get_sparql_endpoint()
 
+            result_format = options.get("result_format")
+            if result_format is None:
+                result_format = "construct" if self._is_construct_query(query) else "bindings"
+
+            if result_format == "construct":
+                self.progress_tracker.update_tracking(
+                    tracking_id, message="Sending CONSTRUCT query to Blazegraph endpoint..."
+                )
+                response = requests.post(
+                    sparql_endpoint,
+                    data={"query": query},
+                    headers={
+                        "Content-Type": "application/x-www-form-urlencoded",
+                        "Accept": "text/turtle",
+                    },
+                    timeout=self.timeout,
+                    auth=(self.username, self.password)
+                    if self.username and self.password
+                    else None,
+                )
+
+                response.raise_for_status()
+
+                self.progress_tracker.update_tracking(
+                    tracking_id, message="Parsing CONSTRUCT response as Turtle..."
+                )
+                graph = Graph()
+                try:
+                    graph.parse(data=response.content, format="turtle")
+                except Exception as parse_error:
+                    raise ProcessingError(
+                        f"Failed to parse CONSTRUCT response as Turtle: {parse_error}"
+                    ) from parse_error
+
+                triples = [(str(s), str(p), str(o)) for s, p, o in graph]
+
+                result = {
+                    "success": True,
+                    "bindings": [],
+                    "variables": [],
+                    "triples": triples,
+                    "metadata": {
+                        "query": query,
+                        "endpoint": sparql_endpoint,
+                        "result_format": "construct",
+                    },
+                }
+
+                self.progress_tracker.stop_tracking(
+                    tracking_id,
+                    status="completed",
+                    message=f"CONSTRUCT query executed: {len(triples)} triples",
+                )
+                return result
+
+            # Non-CONSTRUCT path — unchanged from prior behavior.
             self.progress_tracker.update_tracking(
                 tracking_id, message="Sending query to Blazegraph endpoint..."
             )
@@ -307,31 +393,12 @@ class BlazegraphStore:
         - Known prefixed names: ``xsd:integer``, ``rdf:langString``, etc.
 
         Raises ValueError for anything else.
+
+        Delegates to the shared sparql_escaping.resolve_datatype_iri so this
+        logic has one canonical implementation shared with the CONSTRUCT
+        template renderer (semantica/triplet_store/construct_templates.py).
         """
-        datatype = str(datatype)
+        return sparql_escaping.resolve_datatype_iri(datatype)
-
-        # Already angle-bracketed — validate the inner IRI contains no whitespace
-        if datatype.startswith("<") and datatype.endswith(">"):
-            inner = datatype[1:-1]
-            if not inner or re.search(r"[\s<>\"{}|\\^`]", inner):
-                raise ValueError(f"Invalid datatype IRI: {datatype!r}")
-            return datatype
-
-        # Full absolute IRI without brackets
-        parsed = urlparse(datatype)
-        if parsed.scheme in {"http", "https", "urn"} and not re.search(r"[\s<>\"{}|\\^`]", datatype):
-            return f"<{datatype}>"
-
-        # Prefixed form — expand known prefixes only
-        if ":" in datatype:
-            prefix, local = datatype.split(":", 1)
-            if prefix in self._KNOWN_PREFIXES and re.match(r"^[A-Za-z0-9_\-\.]+$", local):
-                return f"<{self._KNOWN_PREFIXES[prefix]}{local}>"
-
-        raise ValueError(
-            f"Unsupported datatype {datatype!r}: use a full IRI (http/https/urn), "
-            f"an angle-bracketed IRI, or a known prefix (xsd/rdf/rdfs/owl/skos)."
-        )
 
     def _is_uri_value(self, value: str) -> bool:
         """Detect if a value should be serialized as an IRI."""
@@ -346,15 +413,13 @@ class BlazegraphStore:
         return not re.search(r"\s", value)
 
     def _escape_literal(self, value: str) -> str:
-        """Escape string literal for SPARQL."""
+        """Escape string literal for SPARQL.
-        return (
+
-            str(value)
+        Delegates to the shared sparql_escaping.escape_literal so this logic
-            .replace("\\", "\\\\")
+        has one canonical implementation shared with the CONSTRUCT template
-            .replace("\"", "\\\"")
+        renderer (semantica/triplet_store/construct_templates.py).
-            .replace("\n", "\\n")
+        """
-            .replace("\r", "\\r")
+        return sparql_escaping.escape_literal(value)
-            .replace("\t", "\\t")
-        )
 
     def add_triplet(self, triplet: Triplet, **options) -> Dict[str, Any]:
         """Add single triplet."""

semantica/triplet_store/construct_templates.py

@@ -0,0 +1,723 @@
+"""
+SPARQL CONSTRUCT Query Templates (Blazegraph-only)
+
+This module provides parameterized SPARQL CONSTRUCT query templates: a
+`ConstructTemplate` defines a reusable CONSTRUCT query body with `{{param}}`
+placeholders, `ConstructTemplateRegistry` stores/retrieves templates by name,
+and `render_construct_template` safely substitutes parameter values into a
+validated, injection-safe SPARQL string.
+
+This module is intentionally Blazegraph-only. `execute_construct_template`
+renders a template, executes it via `store_backend.execute_sparql(...,
+result_format="construct")` (the Blazegraph CONSTRUCT-aware extension),
+converts the parsed RDF triples into `Triplet` objects, and persists them via
+`store_backend.add_triplets`.
+
+All literal escaping, URI allowlist validation, and datatype-IRI resolution
+is delegated to the shared `semantica.triplet_store.sparql_escaping` module —
+no escaping/validation logic is reimplemented here.
+
+Main Classes:
+    - ParameterDescriptor: Declares one template parameter's name/type/validation.
+    - ConstructTemplate: Named, reusable CONSTRUCT query definition.
+    - ConstructTemplateRegistry: Stores and retrieves ConstructTemplate instances.
+
+Main Functions:
+    - render_construct_template: Safely render a ConstructTemplate into SPARQL.
+    - execute_construct_template: Render, execute, parse, and persist in one call.
+
+Author: Semantica Contributors
+License: MIT
+"""
+
+import re
+from dataclasses import dataclass, field
+from typing import Any, Dict, List, Literal, Optional, Tuple
+
+from ..semantic_extract.triplet_extractor import Triplet
+from ..utils.exceptions import ProcessingError, ValidationError
+from ..utils.logging import get_logger
+from .sparql_escaping import escape_literal, resolve_datatype_iri, validate_uri
+
+ParameterKind = Literal["uri", "literal", "typed-literal"]
+
+# XSD local names (case-insensitive) that render as unquoted numeric/boolean
+# literals rather than quoted "<value>"^^<iri> literals. Matched against the
+# local name of the *resolved* datatype IRI so this works whether the
+# descriptor's datatype was given as a prefixed name (xsd:integer), a full
+# IRI, or a bracketed IRI.
+_INTEGER_LOCAL_NAMES = frozenset({"integer", "int", "long", "short"})
+_DECIMAL_LOCAL_NAMES = frozenset({"decimal", "double", "float"})
+_BOOLEAN_LOCAL_NAMES = frozenset({"boolean"})
+_NUMERIC_UNQUOTED_LOCAL_NAMES = _INTEGER_LOCAL_NAMES | _DECIMAL_LOCAL_NAMES | _BOOLEAN_LOCAL_NAMES
+
+_CONSTRUCT_KEYWORD_RE = re.compile(r"\bCONSTRUCT\b", re.IGNORECASE)
+_WHERE_KEYWORD_RE = re.compile(r"\bWHERE\b", re.IGNORECASE)
+_PLACEHOLDER_RE = re.compile(r"\{\{|\}\}")
+
+
+@dataclass
+class ParameterDescriptor:
+    """Describes one substitution parameter accepted by a ConstructTemplate."""
+
+    name: str
+    """Placeholder name as it appears in the query body, e.g. "subject" for {{subject}}."""
+
+    type: ParameterKind = "literal"
+    """One of "uri" | "literal" | "typed-literal"."""
+
+    required: bool = True
+    """If True and no value/default is supplied at render time, render raises ValidationError."""
+
+    default: Optional[Any] = None
+    """Used when the caller omits this parameter and required=False."""
+
+    datatype: Optional[str] = None
+    """Only meaningful when type == "typed-literal". An XSD datatype token accepted by
+    the shared resolve_datatype_iri, e.g. "xsd:integer", "xsd:dateTime", or a full IRI.
+    Required when type == "typed-literal"; render_construct_template (and
+    ConstructTemplateRegistry.register) raise ValidationError if type == "typed-literal"
+    and datatype is None."""
+
+    language: Optional[str] = None
+    """Only meaningful when type == "literal". RFC 5646 language tag, e.g. "en"."""
+
+
+@dataclass
+class ConstructTemplate:
+    """Parameterized SPARQL CONSTRUCT query template."""
+
+    name: str
+    """Unique registry key, e.g. "person_to_foaf"."""
+
+    description: str
+    """Human-readable summary, shown by list()/get_template_info()."""
+
+    construct_query: str
+    """Full CONSTRUCT query body containing {{param}} placeholders, e.g.:
+    "CONSTRUCT { <{{subject}}> foaf:name {{name}} } WHERE { ... }"
+    Must contain the CONSTRUCT keyword — enforced at register() time, not at
+    dataclass construction time."""
+
+    parameters: List[ParameterDescriptor] = field(default_factory=list)
+    """Ordered list of accepted parameters. Order has no runtime meaning, only used for
+    documentation / get_template_info() output."""
+
+    target_graph: Optional[str] = None
+    """Optional default named-graph IRI used when render_construct_template's/
+    execute_construct_template's target_graph argument is not supplied. This value,
+    like any caller-supplied target_graph, is ALWAYS passed through the same
+    validate_uri/escape path as a "uri"-typed parameter before being interpolated —
+    never through a raw f-string."""
+
+    metadata: dict = field(default_factory=dict)
+    """Free-form, mirrors PipelineTemplate.metadata (e.g. {"category": "rdf_mapping"})."""
+
+
+class ConstructTemplateRegistry:
+    """
+    CONSTRUCT template management system (Blazegraph-only).
+
+    Method shape mirrors PipelineTemplateManager:
+        PipelineTemplateManager.register_template(template) -> None
+        PipelineTemplateManager.get_template(name) -> Optional[PipelineTemplate]
+        PipelineTemplateManager.list_templates(category=None) -> List[str]
+
+    Unlike PipelineTemplateManager.register_template (which silently overwrites
+    by name), this registry rejects duplicate names with ValidationError —
+    CONSTRUCT queries execute against real triple stores, so silent overwrite
+    is a correctness hazard.
+    """
+
+    def __init__(self, config: Optional[Dict[str, Any]] = None, **kwargs):
+        """
+        Initialize template registry.
+
+        Args:
+            config: Configuration dictionary.
+            **kwargs: Additional configuration options.
+        """
+        self.logger = get_logger("construct_template_registry")
+        self.config = config or {}
+        self.config.update(kwargs)
+        self.templates: Dict[str, ConstructTemplate] = {}
+
+    def register(self, template: ConstructTemplate) -> None:
+        """
+        Register a CONSTRUCT template.
+
+        Args:
+            template: ConstructTemplate to register.
+
+        Raises:
+            ValidationError: if template.name is already registered,
+                construct_query does not contain the CONSTRUCT keyword, or any
+                ParameterDescriptor with type == "typed-literal" is missing
+                datatype. Validation happens before any mutation — a failed
+                register() call never partially overwrites the registry.
+        """
+        if template.name in self.templates:
+            raise ValidationError(
+                f"Template already registered: {template.name!r}. "
+                f"Remove it first via remove() if you intend to replace it."
+            )
+
+        if not _CONSTRUCT_KEYWORD_RE.search(template.construct_query):
+            raise ValidationError(
+                f"Template {template.name!r}: construct_query does not contain "
+                f"the CONSTRUCT keyword."
+            )
+
+        for descriptor in template.parameters:
+            if descriptor.type == "typed-literal" and descriptor.datatype is None:
+                raise ValidationError(
+                    f"Template {template.name!r}: parameter {descriptor.name!r} has "
+                    f"type='typed-literal' but no datatype declared."
+                )
+
+        self.templates[template.name] = template
+        self.logger.info(f"Registered CONSTRUCT template: {template.name}")
+
+    def get(self, name: str) -> Optional[ConstructTemplate]:
+        """
+        Get template by name.
+
+        Mirrors PipelineTemplateManager.get_template(template_name) -> Optional[PipelineTemplate].
+        """
+        return self.templates.get(name)
+
+    def list(self, category: Optional[str] = None) -> List[str]:
+        """
+        List registered template names, optionally filtered by metadata["category"].
+
+        Mirrors PipelineTemplateManager.list_templates(category=None) -> List[str].
+        """
+        if category:
+            return [
+                name
+                for name, template in self.templates.items()
+                if template.metadata.get("category") == category
+            ]
+        return list(self.templates.keys())
+
+    def remove(self, name: str) -> bool:
+        """
+        Remove a template by name.
+
+        Returns:
+            True if a template was removed, False if name was not registered.
+        """
+        if name in self.templates:
+            del self.templates[name]
+            self.logger.info(f"Removed CONSTRUCT template: {name}")
+            return True
+        return False
+
+    # --- PipelineTemplateManager-name aliases, for call-site consistency ---
+
+    def register_template(self, template: ConstructTemplate) -> None:
+        """Alias for register(), matching PipelineTemplateManager.register_template."""
+        self.register(template)
+
+    def get_template(self, template_name: str) -> Optional[ConstructTemplate]:
+        """Alias for get(), matching PipelineTemplateManager.get_template."""
+        return self.get(template_name)
+
+    def list_templates(self, category: Optional[str] = None) -> List[str]:
+        """Alias for list(), matching PipelineTemplateManager.list_templates."""
+        return self.list(category)
+
+    def get_template_info(self, template_name: str) -> Optional[Dict[str, Any]]:
+        """
+        Get template information.
+
+        Mirrors PipelineTemplateManager.get_template_info.
+
+        Returns:
+            {"name", "description", "parameter_count", "target_graph", "metadata"}
+            or None if template_name is not registered.
+        """
+        template = self.get(template_name)
+        if not template:
+            return None
+
+        return {
+            "name": template.name,
+            "description": template.description,
+            "parameter_count": len(template.parameters),
+            "target_graph": template.target_graph,
+            "metadata": template.metadata,
+        }
+
+
+# ---------------------------------------------------------------------------
+# render_construct_template and its internal helpers
+# ---------------------------------------------------------------------------
+
+
+def _local_name_of_datatype_iri(datatype_iri: str) -> str:
+    """Extract the lower-cased local name from a resolved (bracketed) datatype IRI."""
+    inner = datatype_iri[1:-1] if datatype_iri.startswith("<") and datatype_iri.endswith(">") else datatype_iri
+    if "#" in inner:
+        return inner.rsplit("#", 1)[1].lower()
+    if "/" in inner:
+        return inner.rsplit("/", 1)[1].lower()
+    return inner.lower()
+
+
+def _render_numeric_literal(value: Any, local_name: str, descriptor_name: str) -> str:
+    """
+    Render an unquoted numeric/boolean literal for a "typed-literal" parameter
+    whose resolved datatype local name is in _NUMERIC_UNQUOTED_LOCAL_NAMES.
+
+    Raises:
+        ValidationError: if value cannot be coerced to the declared datatype.
+    """
+    if local_name in _INTEGER_LOCAL_NAMES:
+        if isinstance(value, bool):
+            raise ValidationError(
+                f"Parameter {descriptor_name!r}: expected an integer value for "
+                f"datatype local name {local_name!r}, got boolean {value!r}."
+            )
+        try:
+            return str(int(str(value)))
+        except (TypeError, ValueError):
+            raise ValidationError(
+                f"Parameter {descriptor_name!r}: value {value!r} is not a valid "
+                f"integer for its declared XSD datatype."
+            )
+
+    if local_name in _DECIMAL_LOCAL_NAMES:
+        try:
+            return str(float(str(value)))
+        except (TypeError, ValueError):
+            raise ValidationError(
+                f"Parameter {descriptor_name!r}: value {value!r} is not a valid "
+                f"decimal/double/float for its declared XSD datatype."
+            )
+
+    if local_name in _BOOLEAN_LOCAL_NAMES:
+        if isinstance(value, bool):
+            return "true" if value else "false"
+        normalized = str(value).strip().lower()
+        if normalized in ("true", "1"):
+            return "true"
+        if normalized in ("false", "0"):
+            return "false"
+        raise ValidationError(
+            f"Parameter {descriptor_name!r}: value {value!r} is not a valid "
+            f"boolean for its declared XSD datatype."
+        )
+
+    raise ValidationError(
+        f"Parameter {descriptor_name!r}: datatype local name {local_name!r} is not "
+        f"a recognized unquoted-numeric XSD datatype."
+    )
+
+
+def _find_matching_brace(text: str, open_index: int) -> int:
+    """
+    Given the index of an opening '{' in text, return the index of its matching '}'.
+
+    Skips over double-quoted string literal content while scanning, so a '{'
+    or '}' character that appears *inside* a rendered literal value (e.g. a
+    "typed-literal"/"literal" parameter whose value contains a brace
+    character — braces are not among the characters escape_literal escapes,
+    since SPARQL/Turtle string literals don't require it) does not corrupt
+    the brace-depth count. Quote-escaping is assumed to follow
+    escape_literal's convention (\\\\ and \\" are the only two-character
+    escapes that can produce a literal backslash or double-quote), so an
+    unescaped '"' reliably toggles in/out of string-literal content.
+    """
+    depth = 0
+    in_string = False
+    i = open_index
+    while i < len(text):
+        ch = text[i]
+        if in_string:
+            if ch == "\\":
+                # Skip the escaped character (e.g. \" or \\) without
+                # inspecting it, matching escape_literal's escaping scheme.
+                i += 2
+                continue
+            if ch == '"':
+                in_string = False
+        else:
+            if ch == '"':
+                in_string = True
+            elif ch == "{":
+                depth += 1
+            elif ch == "}":
+                depth -= 1
+                if depth == 0:
+                    return i
+        i += 1
+    raise ValidationError("Unbalanced braces in construct_query: no matching '}' found.")
+
+
+def _split_construct_query(query_body: str) -> Tuple[str, str, str]:
+    """
+    Split a fully-substituted CONSTRUCT query into (preamble, construct_clause,
+    where_body), so the WHERE body can be re-wrapped in a GRAPH clause for
+    target_graph support.
+
+    Args:
+        query_body: Fully-substituted query string (all {{name}} tokens
+            already replaced).
+
+    Returns:
+        preamble: Everything before the CONSTRUCT keyword (e.g. PREFIX
+            declarations), stripped of leading/trailing whitespace. Preserved
+            verbatim so PREFIX declarations are not silently dropped when
+            target_graph wrapping rewrites the CONSTRUCT/WHERE structure.
+        construct_clause: The raw "{ ... }" template graph pattern immediately
+            following CONSTRUCT, braces included.
+        where_body: The raw text *inside* the "{ ... }" following WHERE,
+            braces excluded.
+
+    Raises:
+        ValidationError: if the CONSTRUCT/WHERE structure cannot be located.
+    """
+    construct_match = _CONSTRUCT_KEYWORD_RE.search(query_body)
+    if not construct_match:
+        raise ValidationError("construct_query does not contain the CONSTRUCT keyword.")
+    preamble = query_body[: construct_match.start()].strip()
+
+    construct_open = query_body.find("{", construct_match.end())
+    if construct_open == -1:
+        raise ValidationError("construct_query is missing '{' after the CONSTRUCT keyword.")
+    construct_close = _find_matching_brace(query_body, construct_open)
+    construct_clause = query_body[construct_open : construct_close + 1]
+
+    where_match = _WHERE_KEYWORD_RE.search(query_body, construct_close + 1)
+    if not where_match:
+        raise ValidationError("construct_query is missing a WHERE clause.")
+    where_open = query_body.find("{", where_match.end())
+    if where_open == -1:
+        raise ValidationError("construct_query is missing '{' after the WHERE keyword.")
+    where_close = _find_matching_brace(query_body, where_open)
+    where_body = query_body[where_open + 1 : where_close]
+
+    return preamble, construct_clause, where_body
+
+
+def render_construct_template(
+    template: ConstructTemplate,
+    params: Dict[str, Any],
+    target_graph: Optional[str] = None,
+) -> str:
+    """
+    Render a ConstructTemplate's construct_query into a safe, executable SPARQL
+    CONSTRUCT query string.
+
+    Args:
+        template: The ConstructTemplate to render.
+        params: Values for each {{name}} placeholder, keyed by ParameterDescriptor.name.
+            Values for missing optional parameters fall back to ParameterDescriptor.default.
+        target_graph: Named graph IRI to wrap the CONSTRUCT query in (via a GRAPH
+            clause around the WHERE body). If None, falls back to
+            template.target_graph. If both are None, no graph wrapping is applied.
+
+    Returns:
+        Fully-substituted SPARQL CONSTRUCT query string, safe to pass directly to
+        BlazegraphStore.execute_sparql.
+
+    Raises:
+        ValidationError: on any of:
+            - a required ParameterDescriptor has no value in params and no default
+            - a "uri"-typed parameter value fails validate_uri
+            - a "typed-literal"-typed parameter is missing template-declared datatype
+            - a "typed-literal"-typed parameter value cannot be coerced to that datatype
+            - target_graph (explicit arg or template.target_graph) fails validate_uri
+            - construct_query references a {{placeholder}} with no matching
+              ParameterDescriptor (detected as an unresolved placeholder after
+              substitution)
+    """
+    # Step 1: Resolve effective parameter values (params override, then default).
+    resolved: Dict[str, Any] = {}
+    for descriptor in template.parameters:
+        if descriptor.name in params:
+            resolved[descriptor.name] = params[descriptor.name]
+        elif not descriptor.required:
+            resolved[descriptor.name] = descriptor.default
+        else:
+            raise ValidationError(
+                f"Missing required parameter: {descriptor.name!r} "
+                f"(template {template.name!r})"
+            )
+
+    # Step 2: Render each parameter value according to its declared type.
+    rendered_values: Dict[str, str] = {}
+    for descriptor in template.parameters:
+        value = resolved[descriptor.name]
+
+        if descriptor.type == "uri":
+            safe_uri = validate_uri(value)
+            rendered_values[descriptor.name] = f"<{safe_uri}>"
+
+        elif descriptor.type == "literal":
+            escaped = escape_literal(value)
+            if descriptor.language is not None:
+                rendered_values[descriptor.name] = f'"{escaped}"@{descriptor.language}'
+            else:
+                rendered_values[descriptor.name] = f'"{escaped}"'
+
+        elif descriptor.type == "typed-literal":
+            if descriptor.datatype is None:
+                raise ValidationError(
+                    f"typed-literal parameter requires datatype: {descriptor.name!r} "
+                    f"(template {template.name!r})"
+                )
+            try:
+                datatype_iri = resolve_datatype_iri(descriptor.datatype)
+            except ValueError as exc:
+                raise ValidationError(
+                    f"Parameter {descriptor.name!r}: {exc}"
+                ) from exc
+
+            local_name = _local_name_of_datatype_iri(datatype_iri)
+            if local_name in _NUMERIC_UNQUOTED_LOCAL_NAMES:
+                rendered_values[descriptor.name] = _render_numeric_literal(
+                    value, local_name, descriptor.name
+                )
+            else:
+                escaped = escape_literal(value)
+                rendered_values[descriptor.name] = f'"{escaped}"^^{datatype_iri}'
+
+        else:
+            raise ValidationError(
+                f"Parameter {descriptor.name!r}: unknown parameter type {descriptor.type!r} "
+                f"(template {template.name!r})"
+            )
+
+    # Step 3: Substitute {{name}} tokens in construct_query.
+    query_body = template.construct_query
+    for name, rendered in rendered_values.items():
+        query_body = query_body.replace("{{" + name + "}}", rendered)
+
+    if _PLACEHOLDER_RE.search(query_body):
+        raise ValidationError(
+            f"Unresolved placeholder(s) in construct_query for template "
+            f"{template.name!r}: query still contains '{{{{' / '}}}}' tokens "
+            f"with no matching ParameterDescriptor."
+        )
+
+    # Step 4: Resolve effective target_graph — SAME validate_uri path as any
+    # "uri" parameter. No raw f-string interpolation is used here.
+    effective_graph = target_graph if target_graph is not None else template.target_graph
+    if effective_graph is not None:
+        safe_graph_uri = validate_uri(effective_graph)
+        wrapped_graph_token = f"<{safe_graph_uri}>"
+
+        preamble, construct_clause, where_body = _split_construct_query(query_body)
+        graph_wrapped_query = (
+            f"CONSTRUCT {construct_clause} "
+            f"WHERE {{ GRAPH {wrapped_graph_token} {{ {where_body} }} }}"
+        )
+        rendered_query = f"{preamble}\n{graph_wrapped_query}" if preamble else graph_wrapped_query
+    else:
+        rendered_query = query_body
+
+    return rendered_query
+
+
+def execute_construct_template(
+    template: ConstructTemplate,
+    params: Dict[str, Any],
+    store_backend: Any,
+    target_graph: Optional[str] = None,
+    **options: Any,
+) -> List[Triplet]:
+    """
+    Render, execute, parse, and persist a CONSTRUCT template in one call.
+
+    Args:
+        template: ConstructTemplate to execute.
+        params: Parameter values, forwarded to render_construct_template.
+        store_backend: A BlazegraphStore instance (Blazegraph-only; duck-typed
+            via hasattr(store_backend, "execute_sparql"), but this function
+            additionally requires store_backend to expose add_triplets — a
+            plain SPARQL-only backend without write support is rejected with
+            ProcessingError).
+        target_graph: Forwarded to render_construct_template; also used as
+            the `graph` option when persisting results via add_triplets so
+            constructed triples land in the same named graph they were
+            scoped to at query time.
+        **options: Forwarded to both store_backend.execute_sparql and
+            store_backend.add_triplets (e.g. timeout overrides).
+
+    Returns:
+        The List[Triplet] that were constructed AND successfully persisted
+        via add_triplets. Order matches the order the store backend's
+        execute_sparql yielded triples in its "triples" key.
+
+    Raises:
+        ValidationError: propagated from render_construct_template.
+        ProcessingError: if store_backend lacks execute_sparql/add_triplets,
+            or if persistence via add_triplets does not report success.
+
+    Exception-propagation convention:
+        This function does not wrap or catch exceptions raised by
+        render_construct_template or store_backend.execute_sparql — each
+        sub-layer is responsible for raising its own correctly-typed
+        exception (ValidationError for rendering failures; ProcessingError
+        for execution failures, as BlazegraphStore.execute_sparql already
+        does internally for connection/request/Turtle-parse errors). Adding
+        a second wrapping layer here would only obscure the original error
+        with no new information. The one exception this function DOES raise
+        itself is the add_triplets write-failure case immediately below,
+        because add_triplets signals failure via a returned dict rather than
+        an exception, so there is no pre-existing typed exception to let
+        propagate.
+    """
+    if not (hasattr(store_backend, "execute_sparql") and hasattr(store_backend, "add_triplets")):
+        raise ProcessingError(
+            "store_backend must support both execute_sparql and add_triplets "
+            "to use execute_construct_template."
+        )
+
+    # Step 1: Render (raises ValidationError unchanged on any failure).
+    rendered_query = render_construct_template(template, params, target_graph)
+
+    # Step 2: Execute via Blazegraph's CONSTRUCT-aware path.
+    query_result = store_backend.execute_sparql(
+        rendered_query, result_format="construct", **options
+    )
+
+    # Step 3: Convert parsed RDF triples to Triplet objects. store_backend is
+    # a BlazegraphStore instance, whose execute_sparql returns Dict[str, Any]
+    # with a "triples" key for CONSTRUCT queries (see BlazegraphStore.execute_sparql).
+    raw_triples = query_result.get("triples", [])
+    triplets: List[Triplet] = []
+    for s, p, o in raw_triples:
+        triplets.append(
+            Triplet(
+                subject=str(s),
+                predicate=str(p),
+                object=str(o),
+                # confidence=1.0 (explicit, matching Triplet's own default):
+                # a CONSTRUCT query is a deterministic graph transformation
+                # over already-persisted RDF/SPARQL-computed data, not a
+                # probabilistic extraction (unlike NER/LLM-based Triplet
+                # extraction, where confidence reflects genuine estimation
+                # uncertainty). There is no meaningful uncertainty to encode
+                # here, so full confidence is the correct value, not an
+                # accidental default.
+                confidence=1.0,
+                metadata={"source": "construct_template", "template": template.name},
+            )
+        )
+
+    # Step 4: Persist via add_triplets (same write path as any other bulk load).
+    effective_graph = target_graph if target_graph is not None else template.target_graph
+    write_result = store_backend.add_triplets(triplets, graph=effective_graph, **options)
+
+    if not write_result.get("success", False):
+        raise ProcessingError(
+            f"Failed to persist constructed triples for template "
+            f"{template.name!r}: {write_result}"
+        )
+
+    return triplets
+
+
+def construct_template_step_handler(data: Any, **options: Any) -> List[Triplet]:
+    """
+    Pipeline step handler for the "construct_template" step type.
+
+    Resolves `store_backend` and `construct_template_registry` from execution
+    options, looks up the named template, and delegates to
+    execute_construct_template. Mirrors the exact resolution pattern used for
+    `triplet_store`/`version_manager` in
+    ExecutionEngine._execute_step's delta_mode handling: call-time options
+    first, engine config fallback second, ProcessingError if either is
+    missing.
+
+    Called by ExecutionEngine._execute_step as
+    `step.handler(data, **step.config, **options)` — no change to
+    PipelineStep or _execute_step is required, since step.config and
+    **options already flow through generically for any step type.
+
+    Args:
+        data: Pipeline data flowing in (unused by this step type — a
+            construct_template step's output is independent of upstream
+            step data, exactly like other non-delta step types).
+        **options: The merged step.config + execution-time options dict, as
+            passed by ExecutionEngine._execute_step's
+            `step.handler(data, **step.config, **options)` call. Expected
+            keys:
+                - template_name: str — required, key into
+                  construct_template_registry.
+                - params: Dict[str, Any] — required, forwarded to
+                  render_construct_template.
+                - target_graph: Optional[str] — optional.
+                - store_backend: Any — resolved from options directly, or
+                  from an "engine_config" dict passed alongside it (see
+                  below); required.
+                - construct_template_registry: ConstructTemplateRegistry —
+                  resolved the same way; required.
+                - engine_config: Optional[Dict[str, Any]] — fallback source
+                  for store_backend/construct_template_registry when not
+                  present directly in options, mirroring the *shape* of
+                  self.config.get(...) in ExecutionEngine._execute_step's
+                  delta_mode handling. One real difference from delta_mode:
+                  delta_mode's fallback runs inside _execute_step itself (a
+                  bound ExecutionEngine method with direct access to
+                  self.config), whereas construct_template_step_handler is a
+                  plain function with no such access — by design, this step
+                  type requires no pre-handler interception in
+                  _execute_step (see Requirement 7.5), so self.config is
+                  simply never threaded to any step.handler call today. In
+                  practice this means store_backend/construct_template_registry
+                  should normally be passed as call-time options via
+                  ExecutionEngine.execute_pipeline(pipeline, data,
+                  store_backend=..., construct_template_registry=...),
+                  which flow through untouched to this handler. The
+                  engine_config parameter exists for callers who explicitly
+                  forward their own ExecutionEngine(config=...) dict into
+                  execute_pipeline's options (e.g. engine_config=engine.config)
+                  and want the same two-tier resolution shape as delta_mode.
+                - step_name: Optional[str] — used only to name the failing
+                  step in error messages; defaults to "construct_template"
+                  if not supplied (design.md's own pseudocode references
+                  step.name inside this handler, but the actual
+                  step.handler(data, **step.config, **options) invocation
+                  never passes step.name to a standalone handler function —
+                  this default covers that gap without requiring any
+                  ExecutionEngine/_execute_step change).
+
+    Returns:
+        The List[Triplet] returned by execute_construct_template.
+
+    Raises:
+        ProcessingError: if store_backend or construct_template_registry
+            cannot be resolved from options (or its "engine_config" fallback).
+        ValidationError: if template_name is not registered in the resolved
+            construct_template_registry.
+    """
+    step_name = options.get("step_name", "construct_template")
+    engine_config = options.get("engine_config") or {}
+
+    store_backend = options.get("store_backend") or engine_config.get("store_backend")
+    construct_template_registry = options.get(
+        "construct_template_registry"
+    ) or engine_config.get("construct_template_registry")
+
+    if not store_backend or not construct_template_registry:
+        raise ProcessingError(
+            f"Step '{step_name}' requires 'store_backend' and "
+            f"'construct_template_registry' in execution options for "
+            f"construct_template processing."
+        )
+
+    template_name = options.get("template_name")
+    template = construct_template_registry.get(template_name)
+    if template is None:
+        raise ValidationError(f"Unknown construct template: {template_name!r}")
+
+    return execute_construct_template(
+        template=template,
+        params=options.get("params", {}),
+        store_backend=store_backend,
+        target_graph=options.get("target_graph"),
+    )

semantica/triplet_store/query_engine.py

@@ -49,6 +49,12 @@ class QueryResult:
     variables: List[str]
     execution_time: float = 0.0
     metadata: Dict[str, Any] = field(default_factory=dict)
+    triples: List[tuple] = field(default_factory=list)
+    """Populated only for CONSTRUCT queries. Each element is a (subject,
+    predicate, object) string 3-tuple, taken directly from the store
+    backend's execute_sparql "triples" key (see BlazegraphStore.execute_sparql
+    CONSTRUCT path). Empty list for all SELECT/ASK/DESCRIBE queries and for
+    backends without CONSTRUCT support."""
 
 
 @dataclass
@@ -183,6 +189,7 @@ class QueryEngine:
                 bindings=result_data.get("bindings", []),
                 variables=result_data.get("variables", []),
                 execution_time=execution_time,
+                triples=result_data.get("triples", []),
                 metadata={
                     **result_data.get("metadata", {}),
                     "optimized": optimized_query != prepared_query,

semantica/triplet_store/sparql_escaping.py

@@ -0,0 +1,159 @@
+"""
+Shared SPARQL literal-escaping and URI-validation primitives.
+
+This module centralizes string-escaping, datatype-IRI resolution, and URI
+allowlist validation logic that was previously duplicated (or would have
+been duplicated) between ``BlazegraphStore`` and the CONSTRUCT template
+renderer. ``BlazegraphStore._escape_literal`` and
+``BlazegraphStore._resolve_datatype_iri`` delegate to ``escape_literal`` and
+``resolve_datatype_iri`` here without any change in behavior; ``validate_uri``
+is new and is used by ``render_construct_template`` for both ``"uri"``-typed
+parameters and ``target_graph`` values.
+
+Author: Semantica Contributors
+License: MIT
+"""
+
+import re
+from typing import FrozenSet
+from urllib.parse import urlparse
+
+from ..utils.exceptions import ValidationError
+
+# Allowed URI schemes for validate_uri's allowlist (Requirement 3.2/4.4).
+_ALLOWED_URI_SCHEMES: FrozenSet[str] = frozenset({"http", "https", "urn"})
+
+# Known prefix expansions for XSD and common RDF vocabularies.
+# Identical table to BlazegraphStore._KNOWN_PREFIXES.
+KNOWN_PREFIXES: dict = {
+    "xsd": "http://www.w3.org/2001/XMLSchema#",
+    "rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+    "rdfs": "http://www.w3.org/2000/01/rdf-schema#",
+    "owl": "http://www.w3.org/2002/07/owl#",
+    "skos": "http://www.w3.org/2004/02/skos/core#",
+}
+
+# RFC 5646 language tag: primary subtag optionally followed by '-' + subtags.
+# Identical pattern to BlazegraphStore._LANG_TAG_RE.
+LANG_TAG_RE = re.compile(r"^[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*$")
+
+# Disallowed-character check shared by validate_uri and resolve_datatype_iri,
+# identical to the character class used throughout BlazegraphStore.
+_DISALLOWED_URI_CHARS_RE = re.compile(r"[\s<>\"{}|\\^`]")
+
+
+def escape_literal(value: str) -> str:
+    """
+    Escape a string literal for safe inclusion inside SPARQL double quotes.
+
+    This is a byte-for-byte copy of BlazegraphStore._escape_literal's
+    transformation:
+        \\ -> \\\\ , " -> \\" , \\n -> \\n , \\r -> \\r , \\t -> \\t
+
+    Args:
+        value: Raw literal value (converted via str() first, matching the
+            original method's behavior of accepting non-str inputs).
+
+    Returns:
+        Escaped string safe to place inside a SPARQL/Turtle double-quoted
+        literal.
+    """
+    return (
+        str(value)
+        .replace("\\", "\\\\")
+        .replace("\"", "\\\"")
+        .replace("\n", "\\n")
+        .replace("\r", "\\r")
+        .replace("\t", "\\t")
+    )
+
+
+def resolve_datatype_iri(datatype: str) -> str:
+    """
+    Expand a datatype string to a validated SPARQL IRI token.
+
+    This is a byte-for-byte copy of BlazegraphStore._resolve_datatype_iri's
+    logic and exception behavior (raises ValueError, not ValidationError, to
+    match the original method's existing contract).
+
+    Accepts:
+    - Already-wrapped IRIs: ``<http://...>``
+    - Full IRIs:            ``http://...`` / ``https://...`` / ``urn:...``
+    - Known prefixed names: ``xsd:integer``, ``rdf:langString``, etc.
+
+    Raises:
+        ValueError: for anything else, or for malformed/unsafe IRIs.
+
+    Returns:
+        An angle-bracketed IRI token, e.g. ``<http://www.w3.org/2001/XMLSchema#integer>``.
+    """
+    datatype = str(datatype)
+
+    # Already angle-bracketed — validate the inner IRI contains no whitespace
+    if datatype.startswith("<") and datatype.endswith(">"):
+        inner = datatype[1:-1]
+        if not inner or _DISALLOWED_URI_CHARS_RE.search(inner):
+            raise ValueError(f"Invalid datatype IRI: {datatype!r}")
+        return datatype
+
+    # Full absolute IRI without brackets
+    parsed = urlparse(datatype)
+    if parsed.scheme in {"http", "https", "urn"} and not _DISALLOWED_URI_CHARS_RE.search(datatype):
+        return f"<{datatype}>"
+
+    # Prefixed form — expand known prefixes only
+    if ":" in datatype:
+        prefix, local = datatype.split(":", 1)
+        if prefix in KNOWN_PREFIXES and re.match(r"^[A-Za-z0-9_\-\.]+$", local):
+            return f"<{KNOWN_PREFIXES[prefix]}{local}>"
+
+    raise ValueError(
+        f"Unsupported datatype {datatype!r}: use a full IRI (http/https/urn), "
+        f"an angle-bracketed IRI, or a known prefix (xsd/rdf/rdfs/owl/skos)."
+    )
+
+
+def validate_uri(
+    value: str,
+    *,
+    allowed_schemes: FrozenSet[str] = _ALLOWED_URI_SCHEMES,
+) -> str:
+    """
+    Validate that `value` is a safe absolute IRI using urllib.parse, and
+    return it unchanged (no bracket-wrapping — callers wrap with <...> at
+    render time).
+
+    Uses urllib.parse.urlparse(value):
+      - scheme must be in allowed_schemes (default {"http", "https", "urn"})
+      - the value must not contain whitespace or any of
+        < > " { } | \\ ^ ` characters (same disallowed-character set used by
+        resolve_datatype_iri / BlazegraphStore's existing IRI checks)
+
+    Args:
+        value: Candidate URI/IRI string.
+        allowed_schemes: Set of permitted URI schemes.
+
+    Returns:
+        The validated `value`, unchanged.
+
+    Raises:
+        ValidationError: if value is empty, not a string, has a scheme not in
+            allowed_schemes, or contains a disallowed character.
+    """
+    if not isinstance(value, str) or not value:
+        raise ValidationError(f"Invalid URI: value must be a non-empty string, got {value!r}")
+
+    if _DISALLOWED_URI_CHARS_RE.search(value):
+        raise ValidationError(
+            f"Invalid URI {value!r}: contains disallowed character(s) "
+            f"(whitespace or one of < > \" {{ }} | \\ ^ `)"
+        )
+
+    parsed = urlparse(value)
+    if parsed.scheme not in allowed_schemes:
+        raise ValidationError(
+            f"Invalid URI {value!r}: scheme {parsed.scheme!r} is not allowed "
+            f"(allowed: {sorted(allowed_schemes)})"
+        )
+
+    return value

tests/triplet_store/test_blazegraph_store.py

@@ -1,7 +1,7 @@
 import unittest
 import os
 import sys
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
 if PROJECT_ROOT not in sys.path:
@@ -9,6 +9,7 @@ if PROJECT_ROOT not in sys.path:
 
 from semantica.semantic_extract.triplet_extractor import Triplet
 from semantica.triplet_store.blazegraph_store import BlazegraphStore
+from semantica.utils.exceptions import ProcessingError
 
 
 class TestBlazegraphStoreSerialization(unittest.TestCase):
@@ -221,5 +222,315 @@ class TestBlazegraphStoreSerialization(unittest.TestCase):
         self.assertEqual(obj, "\"Colour\"@en-GB")
 
 
+from semantica.triplet_store import sparql_escaping
+
+
+class TestSparqlEscapingExtractionParity(unittest.TestCase):
+    """
+    Regression tests proving BlazegraphStore._escape_literal /
+    BlazegraphStore._resolve_datatype_iri are byte-for-byte identical in
+    behavior to the extracted sparql_escaping.escape_literal /
+    sparql_escaping.resolve_datatype_iri functions, across every branch of
+    both original methods.
+    """
+
+    # --- escape_literal: every special character + combinations + plain text ---
+
+    ESCAPE_LITERAL_CASES = [
+        "",  # empty string
+        "plain text, no special chars",
+        "back\\slash",  # backslash
+        'embedded "double" quote',  # double quote
+        "line1\nline2",  # newline
+        "line1\rline2",  # carriage return
+        "tab\there",  # tab
+        "\\\"\n\r\t",  # all five special characters combined
+        'mix \\ and " and \n and \r and \t together',
+        42,  # non-str input (both methods call str(value) first)
+        None,
+    ]
+
+    def test_escape_literal_matches_blazegraph_store_for_every_branch(self):
+        with patch.object(BlazegraphStore, "_connect", autospec=True):
+            store = BlazegraphStore(endpoint="http://localhost:9999/blazegraph")
+        for value in self.ESCAPE_LITERAL_CASES:
+            with self.subTest(value=value):
+                self.assertEqual(
+                    store._escape_literal(value),
+                    sparql_escaping.escape_literal(value),
+                )
+
+    # --- resolve_datatype_iri: every branch (bracketed, full IRI, prefixed,
+    # invalid bracketed, invalid full IRI-with-whitespace, unknown prefix) ---
+
+    RESOLVE_DATATYPE_IRI_VALID_CASES = [
+        "<http://www.w3.org/2001/XMLSchema#integer>",  # already bracketed
+        "http://www.w3.org/2001/XMLSchema#integer",  # full IRI, no brackets
+        "https://example.org/type",  # https scheme
+        "urn:isbn:0451450523",  # urn scheme
+        "xsd:integer",  # known prefix
+        "rdf:langString",  # known prefix
+        "rdfs:label",  # known prefix
+        "owl:Thing",  # known prefix
+        "skos:Concept",  # known prefix
+    ]
+
+    RESOLVE_DATATYPE_IRI_ERROR_CASES = [
+        "<>",  # empty bracketed IRI
+        "<http://example.org/type with space>",  # bracketed IRI with whitespace
+        "<http://example.org/type<injected>",  # bracketed IRI with disallowed char
+        "http://example.org/type CLEAR ALL",  # full IRI with whitespace
+        "myns:customType",  # unknown prefix
+        "not_a_uri_no_colon",  # no scheme, no colon-prefixed form matches
+        "javascript:alert(1)",  # disallowed scheme, not http/https/urn, no known prefix match
+    ]
+
+    def test_resolve_datatype_iri_matches_blazegraph_store_for_valid_cases(self):
+        with patch.object(BlazegraphStore, "_connect", autospec=True):
+            store = BlazegraphStore(endpoint="http://localhost:9999/blazegraph")
+        for datatype in self.RESOLVE_DATATYPE_IRI_VALID_CASES:
+            with self.subTest(datatype=datatype):
+                self.assertEqual(
+                    store._resolve_datatype_iri(datatype),
+                    sparql_escaping.resolve_datatype_iri(datatype),
+                )
+
+    def test_resolve_datatype_iri_matches_blazegraph_store_for_error_cases(self):
+        with patch.object(BlazegraphStore, "_connect", autospec=True):
+            store = BlazegraphStore(endpoint="http://localhost:9999/blazegraph")
+        for datatype in self.RESOLVE_DATATYPE_IRI_ERROR_CASES:
+            with self.subTest(datatype=datatype):
+                store_exc = None
+                shared_exc = None
+                try:
+                    store._resolve_datatype_iri(datatype)
+                except ValueError as exc:
+                    store_exc = exc
+                try:
+                    sparql_escaping.resolve_datatype_iri(datatype)
+                except ValueError as exc:
+                    shared_exc = exc
+
+                self.assertIsNotNone(store_exc, f"Expected ValueError from store for {datatype!r}")
+                self.assertIsNotNone(shared_exc, f"Expected ValueError from shared module for {datatype!r}")
+                self.assertEqual(str(store_exc), str(shared_exc))
+
+
+def _make_connected_store() -> BlazegraphStore:
+    """Create a BlazegraphStore instance bypassing the real _connect() call,
+    with .connected forced True (mirrors the state execute_sparql requires)."""
+    with patch.object(BlazegraphStore, "_connect", autospec=True):
+        store = BlazegraphStore(endpoint="http://localhost:9999/blazegraph")
+    store.connected = True
+    return store
+
+
+class TestBlazegraphStoreConstructExtension(unittest.TestCase):
+    """
+    Tests for the Blazegraph CONSTRUCT extension: _is_construct_query
+    detection, execute_sparql's CONSTRUCT branch (Accept header, Turtle
+    parsing via rdflib, triples shape, ProcessingError on malformed Turtle),
+    and Property 9 (non-CONSTRUCT queries are byte-for-byte unaffected).
+    """
+
+    # --- _is_construct_query detection ---
+
+    def test_is_construct_query_detects_uppercase_keyword(self):
+        store = _make_connected_store()
+        self.assertTrue(store._is_construct_query("CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }"))
+
+    def test_is_construct_query_detects_lowercase_keyword(self):
+        store = _make_connected_store()
+        self.assertTrue(store._is_construct_query("construct { ?s ?p ?o } where { ?s ?p ?o }"))
+
+    def test_is_construct_query_detects_mixed_case_keyword(self):
+        store = _make_connected_store()
+        self.assertTrue(store._is_construct_query("Construct { ?s ?p ?o } Where { ?s ?p ?o }"))
+
+    def test_is_construct_query_false_for_select(self):
+        store = _make_connected_store()
+        self.assertFalse(store._is_construct_query("SELECT ?s WHERE { ?s ?p ?o }"))
+
+    def test_is_construct_query_false_for_ask(self):
+        store = _make_connected_store()
+        self.assertFalse(store._is_construct_query("ASK { ?s ?p ?o }"))
+
+    def test_is_construct_query_does_not_match_substring_inside_identifier(self):
+        # "CONSTRUCTOR" contains "CONSTRUCT" as a substring but must not
+        # match due to \b word-boundary anchoring.
+        store = _make_connected_store()
+        self.assertFalse(
+            store._is_construct_query("SELECT ?s WHERE { ?s <urn:p> \"CONSTRUCTOR\" }")
+        )
+
+    # --- execute_sparql CONSTRUCT path ---
+
+    def test_execute_sparql_construct_sends_turtle_accept_header(self):
+        store = _make_connected_store()
+        mock_response = MagicMock()
+        mock_response.content = (
+            b"@prefix ex: <http://ex.org/> .\n"
+            b'ex:s1 ex:p1 "value1" .\n'
+        )
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response) as mock_post:
+            store.execute_sparql("CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }")
+
+        _, kwargs = mock_post.call_args
+        self.assertEqual(kwargs["headers"]["Accept"], "text/turtle")
+        self.assertEqual(
+            kwargs["headers"]["Content-Type"], "application/x-www-form-urlencoded"
+        )
+
+    def test_execute_sparql_construct_parses_triples_from_fixed_turtle_fixture(self):
+        store = _make_connected_store()
+        turtle_fixture = (
+            b"@prefix ex: <http://ex.org/> .\n"
+            b'ex:s1 ex:p1 "value1" .\n'
+            b"ex:s1 ex:p2 ex:o2 .\n"
+        )
+        mock_response = MagicMock()
+        mock_response.content = turtle_fixture
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response):
+            result = store.execute_sparql("CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }")
+
+        self.assertTrue(result["success"])
+        self.assertEqual(result["bindings"], [])
+        self.assertEqual(result["variables"], [])
+        self.assertEqual(result["metadata"]["result_format"], "construct")
+
+        triples = set(result["triples"])
+        self.assertIn(("http://ex.org/s1", "http://ex.org/p1", "value1"), triples)
+        self.assertIn(("http://ex.org/s1", "http://ex.org/p2", "http://ex.org/o2"), triples)
+        self.assertEqual(len(result["triples"]), 2)
+
+    def test_execute_sparql_construct_result_format_option_forces_construct_path(self):
+        # Even for a query that doesn't literally contain "CONSTRUCT",
+        # result_format="construct" should force the Turtle-parsing path.
+        store = _make_connected_store()
+        mock_response = MagicMock()
+        mock_response.content = b'@prefix ex: <http://ex.org/> .\nex:s1 ex:p1 "v" .\n'
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response) as mock_post:
+            result = store.execute_sparql("SELECT ?s WHERE { ?s ?p ?o }", result_format="construct")
+
+        _, kwargs = mock_post.call_args
+        self.assertEqual(kwargs["headers"]["Accept"], "text/turtle")
+        self.assertIn("triples", result)
+
+    def test_execute_sparql_construct_malformed_turtle_raises_processing_error(self):
+        store = _make_connected_store()
+        mock_response = MagicMock()
+        # Deliberately invalid Turtle syntax.
+        mock_response.content = b"this is { not [ valid turtle syntax at all !!!"
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response):
+            with self.assertRaises(ProcessingError) as ctx:
+                store.execute_sparql("CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }")
+
+        # Must be a ProcessingError, not a raw rdflib exception leaking out.
+        self.assertIsInstance(ctx.exception, ProcessingError)
+        self.assertNotIsInstance(ctx.exception, (SyntaxError, ValueError))
+
+    def test_execute_sparql_construct_handles_literal_with_braces_in_valid_turtle(self):
+        # Adversarial case implied by the brace-matching bug found in the
+        # template-string layer (construct_templates._find_matching_brace):
+        # confirm rdflib itself parses a *valid* Turtle literal containing
+        # brace characters correctly, since this is a different parsing
+        # layer (real Turtle syntax, not our {{param}} template string).
+        store = _make_connected_store()
+        turtle_fixture = (
+            b"@prefix ex: <http://ex.org/> .\n"
+            b'ex:s1 ex:p1 "text with { and } braces inside" .\n'
+        )
+        mock_response = MagicMock()
+        mock_response.content = turtle_fixture
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response):
+            result = store.execute_sparql("CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }")
+
+        self.assertEqual(len(result["triples"]), 1)
+        subject, predicate, obj = result["triples"][0]
+        self.assertEqual(subject, "http://ex.org/s1")
+        self.assertEqual(predicate, "http://ex.org/p1")
+        self.assertEqual(obj, "text with { and } braces inside")
+
+    # --- Property 9: non-CONSTRUCT queries are byte-for-byte unaffected ---
+
+    def test_execute_sparql_select_query_response_shape_unchanged(self):
+        store = _make_connected_store()
+        mock_response = MagicMock()
+        mock_response.json.return_value = {
+            "head": {"vars": ["s", "p", "o"]},
+            "results": {
+                "bindings": [
+                    {
+                        "s": {"type": "uri", "value": "http://ex.org/s1"},
+                        "p": {"type": "uri", "value": "http://ex.org/p1"},
+                        "o": {"type": "literal", "value": "v1"},
+                    }
+                ]
+            },
+        }
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response) as mock_post:
+            result = store.execute_sparql("SELECT ?s ?p ?o WHERE { ?s ?p ?o }")
+
+        # Accept header must NOT be sent for a non-CONSTRUCT query — request
+        # shape is byte-for-byte identical to pre-CONSTRUCT-extension behavior.
+        _, kwargs = mock_post.call_args
+        self.assertEqual(kwargs["headers"], {"Content-Type": "application/x-www-form-urlencoded"})
+        self.assertNotIn("Accept", kwargs["headers"])
+
+        # Response shape must be exactly the pre-existing shape: no "triples"
+        # key at all (not even an empty list) for a plain SELECT response.
+        self.assertEqual(
+            result,
+            {
+                "success": True,
+                "bindings": mock_response.json.return_value["results"]["bindings"],
+                "variables": ["s", "p", "o"],
+                "metadata": {
+                    "query": "SELECT ?s ?p ?o WHERE { ?s ?p ?o }",
+                    "endpoint": store._get_sparql_endpoint(),
+                },
+            },
+        )
+        self.assertNotIn("triples", result)
+
+    def test_execute_sparql_ask_query_uses_bindings_path_not_construct(self):
+        store = _make_connected_store()
+        mock_response = MagicMock()
+        mock_response.json.return_value = {"head": {}, "boolean": True}
+        mock_response.raise_for_status = MagicMock()
+
+        with patch("semantica.triplet_store.blazegraph_store.requests.post", return_value=mock_response) as mock_post:
+            store.execute_sparql("ASK { ?s ?p ?o }")
+
+        _, kwargs = mock_post.call_args
+        self.assertNotIn("Accept", kwargs["headers"])
+
+
+class TestQueryEngineConstructValidation(unittest.TestCase):
+    """
+    Confirms QueryEngine._validate_query requires zero changes for CONSTRUCT
+    support — CONSTRUCT was already a valid keyword before this feature.
+    """
+
+    def test_construct_query_passes_validation_unchanged(self):
+        from semantica.triplet_store.query_engine import QueryEngine
+
+        engine = QueryEngine()
+        query = "CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }"
+        self.assertTrue(engine._validate_query(query))
+
+
 if __name__ == "__main__":
     unittest.main()

tests/triplet_store/test_construct_templates.py

@@ -0,0 +1,966 @@
+"""
+Tests for semantica.triplet_store.construct_templates.
+
+Covers:
+    - ConstructTemplateRegistry: register/get/list/remove + aliases,
+      duplicate-name rejection, registration-time validation errors.
+    - render_construct_template: parametrized coverage of Correctness
+      Properties 1 (literal escaping), 2/3 (URI allowlist + target_graph
+      parity), and 4 (typed-literal numeric rendering), per design.md's
+      "Parametrized coverage of Correctness Properties 1, 2, 3, 4" section.
+"""
+
+import os
+import sys
+import unittest
+from unittest.mock import MagicMock
+
+import pytest
+from rdflib import Graph
+
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+if PROJECT_ROOT not in sys.path:
+    sys.path.insert(0, PROJECT_ROOT)
+
+from semantica.triplet_store.construct_templates import (
+    ConstructTemplate,
+    ConstructTemplateRegistry,
+    ParameterDescriptor,
+    _find_matching_brace,
+    _split_construct_query,
+    construct_template_step_handler,
+    execute_construct_template,
+    render_construct_template,
+)
+from semantica.utils.exceptions import ProcessingError, ValidationError
+
+
+def _simple_template(**overrides) -> ConstructTemplate:
+    """A minimal valid CONSTRUCT template: one literal param, no target_graph."""
+    defaults = dict(
+        name="simple_template",
+        description="A minimal template for testing.",
+        construct_query=(
+            "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+            "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+        ),
+        parameters=[ParameterDescriptor(name="value", type="literal", required=True)],
+    )
+    defaults.update(overrides)
+    return ConstructTemplate(**defaults)
+
+
+def _uri_template(**overrides) -> ConstructTemplate:
+    """A minimal valid CONSTRUCT template with one "uri"-typed param."""
+    defaults = dict(
+        name="uri_template",
+        description="A minimal template with a uri parameter.",
+        construct_query=(
+            "CONSTRUCT { {{subject}} <http://ex.org/p1> \"x\" } "
+            "WHERE { {{subject}} <http://ex.org/p1> \"x\" }"
+        ),
+        parameters=[ParameterDescriptor(name="subject", type="uri", required=True)],
+    )
+    defaults.update(overrides)
+    return ConstructTemplate(**defaults)
+
+
+def _typed_literal_template(datatype: str, **overrides) -> ConstructTemplate:
+    """A minimal valid CONSTRUCT template with one "typed-literal" param."""
+    defaults = dict(
+        name="typed_literal_template",
+        description="A minimal template with a typed-literal parameter.",
+        construct_query=(
+            "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+            "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+        ),
+        parameters=[
+            ParameterDescriptor(
+                name="value", type="typed-literal", required=True, datatype=datatype
+            )
+        ],
+    )
+    defaults.update(overrides)
+    return ConstructTemplate(**defaults)
+
+
+# ---------------------------------------------------------------------------
+# ConstructTemplateRegistry
+# ---------------------------------------------------------------------------
+
+
+class TestConstructTemplateRegistry(unittest.TestCase):
+    def test_register_and_get(self):
+        registry = ConstructTemplateRegistry()
+        template = _simple_template()
+        registry.register(template)
+        self.assertIs(registry.get("simple_template"), template)
+
+    def test_register_duplicate_name_raises_and_does_not_overwrite(self):
+        registry = ConstructTemplateRegistry()
+        t1 = _simple_template(description="original")
+        t2 = _simple_template(description="replacement")
+        registry.register(t1)
+        with self.assertRaises(ValidationError):
+            registry.register(t2)
+        self.assertIs(registry.get("simple_template"), t1)
+        self.assertEqual(registry.get("simple_template").description, "original")
+
+    def test_register_rejects_missing_construct_keyword(self):
+        registry = ConstructTemplateRegistry()
+        bad_template = _simple_template(
+            construct_query="SELECT ?s WHERE { ?s ?p ?o }"
+        )
+        with self.assertRaises(ValidationError):
+            registry.register(bad_template)
+        self.assertIsNone(registry.get("simple_template"))
+
+    def test_register_rejects_typed_literal_without_datatype(self):
+        registry = ConstructTemplateRegistry()
+        bad_template = _simple_template(
+            parameters=[ParameterDescriptor(name="value", type="typed-literal", datatype=None)]
+        )
+        with self.assertRaises(ValidationError):
+            registry.register(bad_template)
+        self.assertIsNone(registry.get("simple_template"))
+
+    def test_get_miss_returns_none(self):
+        registry = ConstructTemplateRegistry()
+        self.assertIsNone(registry.get("nonexistent"))
+
+    def test_list_without_category_returns_all_names(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(_simple_template(name="t1"))
+        registry.register(_simple_template(name="t2"))
+        self.assertEqual(sorted(registry.list()), ["t1", "t2"])
+
+    def test_list_with_category_filters(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(_simple_template(name="t1", metadata={"category": "mapping"}))
+        registry.register(_simple_template(name="t2", metadata={"category": "other"}))
+        registry.register(_simple_template(name="t3", metadata={"category": "mapping"}))
+        self.assertEqual(sorted(registry.list(category="mapping")), ["t1", "t3"])
+        self.assertEqual(registry.list(category="other"), ["t2"])
+        self.assertEqual(registry.list(category="nonexistent_category"), [])
+
+    def test_remove_idempotence(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(_simple_template())
+        self.assertTrue(registry.remove("simple_template"))
+        self.assertIsNone(registry.get("simple_template"))
+        self.assertFalse(registry.remove("simple_template"))
+
+    def test_register_template_alias_delegates_to_register(self):
+        registry = ConstructTemplateRegistry()
+        template = _simple_template()
+        registry.register_template(template)
+        self.assertIs(registry.get("simple_template"), template)
+        # Duplicate via alias still raises, same as register().
+        with self.assertRaises(ValidationError):
+            registry.register_template(_simple_template())
+
+    def test_get_template_alias_delegates_to_get(self):
+        registry = ConstructTemplateRegistry()
+        template = _simple_template()
+        registry.register(template)
+        self.assertIs(registry.get_template("simple_template"), template)
+        self.assertIsNone(registry.get_template("nonexistent"))
+
+    def test_list_templates_alias_delegates_to_list(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(_simple_template(name="t1", metadata={"category": "mapping"}))
+        registry.register(_simple_template(name="t2"))
+        self.assertEqual(sorted(registry.list_templates()), ["t1", "t2"])
+        self.assertEqual(registry.list_templates(category="mapping"), ["t1"])
+
+    def test_get_template_info_returns_expected_shape(self):
+        registry = ConstructTemplateRegistry()
+        template = _simple_template(
+            target_graph="http://ex.org/graphs/g1",
+            metadata={"category": "mapping"},
+        )
+        registry.register(template)
+        info = registry.get_template_info("simple_template")
+        self.assertEqual(
+            info,
+            {
+                "name": "simple_template",
+                "description": "A minimal template for testing.",
+                "parameter_count": 1,
+                "target_graph": "http://ex.org/graphs/g1",
+                "metadata": {"category": "mapping"},
+            },
+        )
+
+    def test_get_template_info_miss_returns_none(self):
+        registry = ConstructTemplateRegistry()
+        self.assertIsNone(registry.get_template_info("nonexistent"))
+
+
+# ---------------------------------------------------------------------------
+# Property 1: literal escaping
+# ---------------------------------------------------------------------------
+
+
+LITERAL_ESCAPING_CASES = [
+    pytest.param("back\\slash", id="backslash"),
+    pytest.param('embedded "double" quote', id="double-quote"),
+    pytest.param("line1\nline2", id="newline"),
+    pytest.param("line1\rline2", id="carriage-return"),
+    pytest.param("tab\there", id="tab"),
+    pytest.param("\\\"\n\r\t", id="all-combined"),
+]
+
+
+class TestRenderConstructTemplateLiteralEscaping:
+    """Property 1: no unescaped injection via literal parameters."""
+
+    @pytest.mark.parametrize("raw_value", LITERAL_ESCAPING_CASES)
+    def test_literal_param_round_trips_through_rdflib_turtle_parser(self, raw_value):
+        template = _simple_template()
+        rendered = render_construct_template(template, params={"value": raw_value})
+
+        # rendered must not contain an unescaped '"' that would terminate the
+        # literal early — verified by successfully round-tripping it through
+        # rdflib's Turtle parser back to the original string.
+        turtle_doc = f"@prefix ex: <http://ex.org/> .\nex:s1 ex:p1 {rendered.split('} WHERE')[0].split('<http://ex.org/p1>')[1].strip().rstrip('}').strip()} ."
+        graph = Graph()
+        graph.parse(data=turtle_doc, format="turtle")
+        literal_values = [str(o) for _, _, o in graph]
+        assert raw_value in literal_values
+
+    def test_render_produces_no_unescaped_quote_break(self):
+        template = _simple_template()
+        rendered = render_construct_template(
+            template, params={"value": 'has "quotes" inside'}
+        )
+        assert '"has \\"quotes\\" inside"' in rendered
+
+
+# ---------------------------------------------------------------------------
+# Property 2/3: URI allowlist + target_graph parity
+# ---------------------------------------------------------------------------
+
+
+BAD_URI_CASES = [
+    pytest.param("javascript:alert(1)", id="javascript-scheme"),
+    pytest.param("file:///etc/passwd", id="file-scheme"),
+    pytest.param("http://example.com/has space", id="embedded-whitespace"),
+    pytest.param("http://example.com/<injected>", id="embedded-angle-brackets"),
+    pytest.param("http://example.com/{injected}", id="embedded-braces"),
+    pytest.param("http://example.com/#frag with space", id="fragment-with-whitespace"),
+    pytest.param("", id="empty-string"),
+]
+
+GOOD_URI_CASES = [
+    pytest.param("http://example.com/ok", id="http-scheme"),
+    pytest.param("https://example.com/ok", id="https-scheme"),
+    pytest.param("urn:isbn:0451450523", id="urn-scheme"),
+]
+
+
+class TestRenderConstructTemplateUriValidation:
+    """Property 2 (URI allowlist enforcement) and Property 3 (target_graph parity)."""
+
+    @pytest.mark.parametrize("bad_uri", BAD_URI_CASES)
+    def test_uri_param_rejects_unsafe_values(self, bad_uri):
+        template = _uri_template()
+        with pytest.raises(ValidationError):
+            render_construct_template(template, params={"subject": bad_uri})
+
+    @pytest.mark.parametrize("bad_uri", BAD_URI_CASES)
+    def test_target_graph_rejects_same_unsafe_values_as_uri_param(self, bad_uri):
+        # A template with a valid "uri" param, but an unsafe target_graph.
+        template = _uri_template()
+        valid_params = {"subject": "http://example.com/ok"}
+
+        with pytest.raises(ValidationError) as uri_param_exc_info:
+            render_construct_template(
+                template, params={"subject": bad_uri}
+            )
+        with pytest.raises(ValidationError) as target_graph_exc_info:
+            render_construct_template(
+                template, params=valid_params, target_graph=bad_uri
+            )
+
+        # Parity check: both failure modes are ValidationError (same type);
+        # for non-empty invalid values, the underlying message text is
+        # identical because both call validate_uri() on the same bad_uri.
+        if bad_uri:
+            assert str(uri_param_exc_info.value) == str(target_graph_exc_info.value)
+
+    @pytest.mark.parametrize("good_uri", GOOD_URI_CASES)
+    def test_uri_param_accepts_allowed_schemes(self, good_uri):
+        template = _uri_template()
+        rendered = render_construct_template(template, params={"subject": good_uri})
+        assert f"<{good_uri}>" in rendered
+
+    @pytest.mark.parametrize("good_uri", GOOD_URI_CASES)
+    def test_target_graph_accepts_same_allowed_schemes_as_uri_param(self, good_uri):
+        template = _uri_template()
+        rendered = render_construct_template(
+            template,
+            params={"subject": "http://example.com/ok"},
+            target_graph=good_uri,
+        )
+        assert f"GRAPH <{good_uri}>" in rendered
+
+    def test_template_target_graph_used_when_argument_omitted(self):
+        template = _uri_template(target_graph="http://ex.org/graphs/default")
+        rendered = render_construct_template(
+            template, params={"subject": "http://example.com/ok"}
+        )
+        assert "GRAPH <http://ex.org/graphs/default>" in rendered
+
+    def test_explicit_target_graph_overrides_template_default(self):
+        template = _uri_template(target_graph="http://ex.org/graphs/default")
+        rendered = render_construct_template(
+            template,
+            params={"subject": "http://example.com/ok"},
+            target_graph="http://ex.org/graphs/override",
+        )
+        assert "GRAPH <http://ex.org/graphs/override>" in rendered
+        assert "GRAPH <http://ex.org/graphs/default>" not in rendered
+
+    def test_no_target_graph_means_no_graph_wrapping(self):
+        template = _uri_template()
+        rendered = render_construct_template(
+            template, params={"subject": "http://example.com/ok"}
+        )
+        assert "GRAPH" not in rendered
+
+
+# ---------------------------------------------------------------------------
+# Property 4: typed-literal numeric rendering
+# ---------------------------------------------------------------------------
+
+
+TYPED_LITERAL_CASES = [
+    pytest.param("xsd:integer", 42, True, id="xsd-integer"),
+    pytest.param("xsd:int", -7, True, id="xsd-int"),
+    pytest.param("xsd:long", 9999999999, True, id="xsd-long"),
+    pytest.param("xsd:short", 12, True, id="xsd-short"),
+    pytest.param("xsd:decimal", 3.14, True, id="xsd-decimal"),
+    pytest.param("xsd:double", 2.5e10, True, id="xsd-double"),
+    pytest.param("xsd:float", 1.5, True, id="xsd-float"),
+    pytest.param("xsd:boolean", True, True, id="xsd-boolean-true"),
+    pytest.param("xsd:boolean", False, True, id="xsd-boolean-false"),
+    pytest.param("xsd:dateTime", "2024-01-01T00:00:00Z", False, id="xsd-datetime-contrast"),
+]
+
+
+class TestRenderConstructTemplateTypedLiteralRendering:
+    """Property 4: typed-literal numeric rendering is unquoted, non-numeric is quoted."""
+
+    @pytest.mark.parametrize("datatype,value,expect_unquoted", TYPED_LITERAL_CASES)
+    def test_typed_literal_rendering_by_datatype(self, datatype, value, expect_unquoted):
+        template = _typed_literal_template(datatype)
+        rendered = render_construct_template(template, params={"value": value})
+
+        # Extract the substituted token from the rendered query.
+        placeholder_start = rendered.index("<http://ex.org/p1>") + len("<http://ex.org/p1> ")
+        placeholder_end = rendered.index(" }", placeholder_start)
+        substituted = rendered[placeholder_start:placeholder_end]
+
+        if expect_unquoted:
+            assert not substituted.startswith('"'), (
+                f"Expected unquoted rendering for {datatype}, got: {substituted!r}"
+            )
+        else:
+            assert substituted.startswith('"') and "^^<" in substituted, (
+                f"Expected quoted ^^<iri> rendering for {datatype}, got: {substituted!r}"
+            )
+
+        # rdflib should parse the resulting triple with the expected Literal.
+        prefix = "@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .\n"
+        turtle_doc = (
+            prefix
+            + f"<http://ex.org/s1> <http://ex.org/p1> {substituted} ."
+        )
+        graph = Graph()
+        graph.parse(data=turtle_doc, format="turtle")
+        literals = [o for _, _, o in graph]
+        assert len(literals) == 1
+
+    def test_typed_literal_rejects_non_numeric_value_for_integer(self):
+        template = _typed_literal_template("xsd:integer")
+        with pytest.raises(ValidationError):
+            render_construct_template(template, params={"value": "not-a-number"})
+
+    def test_typed_literal_missing_datatype_raises(self):
+        template = _simple_template(
+            parameters=[ParameterDescriptor(name="value", type="typed-literal", datatype=None)]
+        )
+        with pytest.raises(ValidationError):
+            render_construct_template(template, params={"value": 42})
+
+
+# ---------------------------------------------------------------------------
+# Required-parameter completeness (Property 5, spot-checked alongside 1-4)
+# ---------------------------------------------------------------------------
+
+
+class TestRenderConstructTemplateRequiredParameters:
+    def test_missing_required_parameter_raises(self):
+        template = _simple_template()
+        with pytest.raises(ValidationError):
+            render_construct_template(template, params={})
+
+    def test_optional_parameter_falls_back_to_default(self):
+        template = _simple_template(
+            parameters=[
+                ParameterDescriptor(name="value", type="literal", required=False, default="fallback")
+            ]
+        )
+        rendered = render_construct_template(template, params={})
+        assert '"fallback"' in rendered
+
+    def test_unresolved_placeholder_with_no_descriptor_raises(self):
+        template = _simple_template(
+            construct_query=(
+                "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} ; "
+                "<http://ex.org/p2> {{undeclared}} } "
+                "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+            )
+        )
+        with pytest.raises(ValidationError):
+            render_construct_template(template, params={"value": "x"})
+
+
+# ---------------------------------------------------------------------------
+# _split_construct_query / _find_matching_brace: CONSTRUCT/WHERE boundary
+# parsing. This logic was added to fill a gap left as unspecified stubs
+# (extract_construct_clause/extract_where_body) in design.md; it is
+# exercised whenever target_graph wrapping is requested.
+# ---------------------------------------------------------------------------
+
+
+class TestSplitConstructQuery(unittest.TestCase):
+    """
+    Direct coverage of _split_construct_query / _find_matching_brace against
+    the 5 scenarios called out for verification, plus a regression case for
+    a bug found during that verification (see test 5b).
+    """
+
+    def test_1_prefix_declarations_before_construct_are_preserved_as_preamble(self):
+        query = (
+            "PREFIX foaf: <http://xmlns.com/foaf/0.1/>\n"
+            'CONSTRUCT { <http://ex.org/s1> foaf:name "Alice" } '
+            'WHERE { <http://ex.org/s1> foaf:name "Alice" }'
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(preamble, "PREFIX foaf: <http://xmlns.com/foaf/0.1/>")
+        self.assertEqual(construct_clause, '{ <http://ex.org/s1> foaf:name "Alice" }')
+        self.assertEqual(where_body.strip(), '<http://ex.org/s1> foaf:name "Alice"')
+
+    def test_1b_target_graph_wrapping_preserves_prefix_preamble(self):
+        # End-to-end: PREFIX preamble must survive graph-wrapping, not just
+        # the standalone splitter.
+        template = ConstructTemplate(
+            name="prefixed_template",
+            description="test",
+            construct_query=(
+                "PREFIX foaf: <http://xmlns.com/foaf/0.1/>\n"
+                'CONSTRUCT { <http://ex.org/s1> foaf:name "Alice" } '
+                'WHERE { <http://ex.org/s1> foaf:name "Alice" }'
+            ),
+        )
+        rendered = render_construct_template(
+            template, params={}, target_graph="http://ex.org/graphs/g1"
+        )
+        self.assertTrue(rendered.startswith("PREFIX foaf: <http://xmlns.com/foaf/0.1/>"))
+        self.assertIn("GRAPH <http://ex.org/graphs/g1>", rendered)
+
+    def test_2_nested_braces_in_construct_clause_blank_node_pattern(self):
+        query = (
+            "CONSTRUCT { ?s ?p [ <http://ex.org/p2> ?o2 ] } "
+            "WHERE { ?s ?p ?o2 }"
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(preamble, "")
+        self.assertEqual(construct_clause, "{ ?s ?p [ <http://ex.org/p2> ?o2 ] }")
+        self.assertEqual(where_body.strip(), "?s ?p ?o2")
+
+    def test_2b_nested_braces_in_construct_clause_graph_pattern(self):
+        # A CONSTRUCT clause containing an actual nested { ... } (not just
+        # blank-node [ ... ] syntax), to directly exercise brace-depth
+        # tracking rather than square-bracket handling.
+        query = (
+            "CONSTRUCT { GRAPH <http://ex.org/g1> { ?s ?p ?o } } "
+            "WHERE { ?s ?p ?o }"
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(construct_clause, "{ GRAPH <http://ex.org/g1> { ?s ?p ?o } }")
+        self.assertEqual(where_body.strip(), "?s ?p ?o")
+
+    def test_3_nested_braces_in_where_clause_optional_block(self):
+        query = (
+            "CONSTRUCT { ?s <http://ex.org/p1> ?o } "
+            "WHERE { ?s <http://ex.org/p1> ?o . OPTIONAL { ?s <http://ex.org/p2> ?o2 } }"
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(construct_clause, "{ ?s <http://ex.org/p1> ?o }")
+        self.assertEqual(
+            where_body.strip(),
+            "?s <http://ex.org/p1> ?o . OPTIONAL { ?s <http://ex.org/p2> ?o2 }",
+        )
+
+    def test_3b_nested_braces_in_where_clause_filter_not_exists_block(self):
+        query = (
+            "CONSTRUCT { ?s <http://ex.org/p1> ?o } "
+            "WHERE { ?s <http://ex.org/p1> ?o . "
+            "FILTER NOT EXISTS { ?s <http://ex.org/p2> ?o2 } }"
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(construct_clause, "{ ?s <http://ex.org/p1> ?o }")
+        self.assertEqual(
+            where_body.strip(),
+            "?s <http://ex.org/p1> ?o . FILTER NOT EXISTS { ?s <http://ex.org/p2> ?o2 }",
+        )
+
+    def test_4_where_keyword_like_substring_inside_construct_clause_literal(self):
+        # "WHERE" appearing inside a string literal in the CONSTRUCT clause
+        # must not be mistaken for the real WHERE keyword.
+        query = (
+            'CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> "the WHERE clause matters" } '
+            "WHERE { <http://ex.org/s1> <http://ex.org/p1> ?o }"
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(
+            construct_clause,
+            '{ <http://ex.org/s1> <http://ex.org/p1> "the WHERE clause matters" }',
+        )
+        self.assertEqual(where_body.strip(), "<http://ex.org/s1> <http://ex.org/p1> ?o")
+
+    def test_4b_brace_character_inside_where_clause_literal_does_not_break_matching(self):
+        # A '}' character embedded inside a string literal within the WHERE
+        # body must not be counted as a real closing brace by
+        # _find_matching_brace (regression test for a bug found during
+        # verification: braces inside literals were originally counted
+        # regardless of string-literal context, corrupting brace-depth
+        # tracking and truncating/duplicating query text).
+        query = (
+            "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> ?o } "
+            'WHERE { <http://ex.org/s1> <http://ex.org/p1> "text with } inside" }'
+        )
+        preamble, construct_clause, where_body = _split_construct_query(query)
+        self.assertEqual(construct_clause, "{ <http://ex.org/s1> <http://ex.org/p1> ?o }")
+        self.assertEqual(
+            where_body.strip(),
+            '<http://ex.org/s1> <http://ex.org/p1> "text with } inside"',
+        )
+
+    def test_4c_end_to_end_literal_with_brace_survives_target_graph_wrapping(self):
+        # End-to-end regression test: a rendered "literal" parameter value
+        # containing a '}' character must survive target_graph wrapping
+        # intact, not get truncated by brace-depth confusion.
+        template = ConstructTemplate(
+            name="brace_in_literal",
+            description="test",
+            construct_query=(
+                "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+                "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+            ),
+            parameters=[ParameterDescriptor(name="value", type="literal", required=True)],
+        )
+        rendered = render_construct_template(
+            template,
+            params={"value": "text with } inside"},
+            target_graph="http://ex.org/graphs/g1",
+        )
+        self.assertIn('"text with } inside"', rendered)
+        # Must appear intact in both the CONSTRUCT clause and the GRAPH-wrapped
+        # WHERE body — not truncated at the embedded '}'.
+        self.assertEqual(rendered.count('"text with } inside"'), 2)
+
+    def test_5_mismatched_braces_more_open_than_close_raises_validation_error(self):
+        query = "CONSTRUCT { ?s ?p ?o WHERE { ?s ?p ?o }"
+        with self.assertRaises(ValidationError):
+            _split_construct_query(query)
+
+    def test_5b_mismatched_braces_end_to_end_via_target_graph_wrapping(self):
+        # End-to-end: a malformed construct_query only surfaces the brace
+        # mismatch when target_graph wrapping is requested (no wrapping
+        # needed => no splitting attempted => no error from this code path).
+        template = ConstructTemplate(
+            name="malformed_template",
+            description="test",
+            construct_query="CONSTRUCT { ?s ?p ?o WHERE { ?s ?p ?o }",
+        )
+        with self.assertRaises(ValidationError):
+            render_construct_template(
+                template, params={}, target_graph="http://ex.org/graphs/g1"
+            )
+
+    def test_find_matching_brace_raises_on_no_closing_brace(self):
+        with self.assertRaises(ValidationError):
+            _find_matching_brace("{ unterminated", 0)
+
+
+# ---------------------------------------------------------------------------
+# execute_construct_template: render -> execute -> convert -> persist.
+# Property 6 (round-trip persistence) coverage via a stub store_backend.
+# ---------------------------------------------------------------------------
+
+
+class _StubStoreBackend:
+    """
+    Minimal stub store_backend for execute_construct_template tests.
+
+    execute_sparql returns a fixed CONSTRUCT-shaped result; add_triplets
+    records exactly what it was called with and returns a caller-controlled
+    success/failure result.
+    """
+
+    def __init__(self, triples, add_triplets_result=None, execute_sparql_error=None):
+        self._triples = triples
+        self._add_triplets_result = add_triplets_result or {"success": True}
+        self._execute_sparql_error = execute_sparql_error
+        self.execute_sparql_calls = []
+        self.add_triplets_calls = []
+
+    def execute_sparql(self, query, **options):
+        self.execute_sparql_calls.append((query, options))
+        if self._execute_sparql_error is not None:
+            raise self._execute_sparql_error
+        return {
+            "success": True,
+            "bindings": [],
+            "variables": [],
+            "triples": self._triples,
+            "metadata": {"query": query, "result_format": "construct"},
+        }
+
+    def add_triplets(self, triplets, **options):
+        self.add_triplets_calls.append((triplets, options))
+        return self._add_triplets_result
+
+
+class TestExecuteConstructTemplate(unittest.TestCase):
+    def _template(self, target_graph=None):
+        return ConstructTemplate(
+            name="exec_test_template",
+            description="test",
+            construct_query=(
+                "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+                "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+            ),
+            parameters=[ParameterDescriptor(name="value", type="literal", required=True)],
+            target_graph=target_graph,
+        )
+
+    # --- 1. Happy path ---
+
+    def test_happy_path_returns_triplets_and_calls_add_triplets_with_same_list(self):
+        fixed_triples = [
+            ("http://ex.org/s1", "http://ex.org/p1", "v1"),
+            ("http://ex.org/s2", "http://ex.org/p2", "v2"),
+        ]
+        stub = _StubStoreBackend(triples=fixed_triples)
+        template = self._template()
+
+        result = execute_construct_template(template, {"value": "x"}, stub)
+
+        self.assertEqual(len(result), 2)
+        self.assertEqual(
+            [(t.subject, t.predicate, t.object) for t in result],
+            fixed_triples,
+        )
+        for triplet in result:
+            self.assertEqual(
+                triplet.metadata, {"source": "construct_template", "template": "exec_test_template"}
+            )
+            # confidence is explicitly 1.0 (documented, deliberate default —
+            # CONSTRUCT results are deterministic, not probabilistic extraction).
+            self.assertEqual(triplet.confidence, 1.0)
+
+        # add_triplets must have been called with exactly this list (same
+        # object, not a copy or a differently-ordered list).
+        self.assertEqual(len(stub.add_triplets_calls), 1)
+        called_triplets, called_options = stub.add_triplets_calls[0]
+        self.assertIs(called_triplets, result)
+
+    # --- 2. Missing add_triplets ---
+
+    def test_missing_add_triplets_raises_before_execute_sparql_is_called(self):
+        class NoAddTriplets:
+            def execute_sparql(self, query, **options):
+                raise AssertionError("execute_sparql must not be called")
+
+        stub = NoAddTriplets()
+        template = self._template()
+
+        with self.assertRaises(ProcessingError):
+            execute_construct_template(template, {"value": "x"}, stub)
+
+    def test_missing_add_triplets_execute_sparql_not_called_verified_via_mock(self):
+        stub = MagicMock()
+        del stub.add_triplets  # hasattr(stub, "add_triplets") -> False
+        template = self._template()
+
+        with self.assertRaises(ProcessingError):
+            execute_construct_template(template, {"value": "x"}, stub)
+
+        stub.execute_sparql.assert_not_called()
+
+    # --- 3. Missing execute_sparql ---
+
+    def test_missing_execute_sparql_raises_before_any_query_attempted(self):
+        stub = MagicMock()
+        del stub.execute_sparql  # hasattr(stub, "execute_sparql") -> False
+        template = self._template()
+
+        with self.assertRaises(ProcessingError):
+            execute_construct_template(template, {"value": "x"}, stub)
+
+        stub.add_triplets.assert_not_called()
+
+    # --- 4. add_triplets reports failure ---
+
+    def test_add_triplets_failure_raises_processing_error_not_partial_list(self):
+        fixed_triples = [("http://ex.org/s1", "http://ex.org/p1", "v1")]
+        stub = _StubStoreBackend(
+            triples=fixed_triples,
+            add_triplets_result={"success": False, "error": "write failed"},
+        )
+        template = self._template()
+
+        with self.assertRaises(ProcessingError):
+            execute_construct_template(template, {"value": "x"}, stub)
+
+        # add_triplets was still attempted (with the constructed triplets)...
+        self.assertEqual(len(stub.add_triplets_calls), 1)
+        # ...but the function must not have returned anything — verified by
+        # the exception itself; there is no return value to inspect because
+        # execute_construct_template raised instead of returning.
+
+    # --- 5. execute_sparql raises an exception ---
+
+    def test_execute_sparql_exception_propagates_without_being_swallowed(self):
+        # Report exactly what happens: execute_construct_template does not
+        # wrap or catch exceptions raised by store_backend.execute_sparql —
+        # it calls it directly and lets whatever it raises propagate as-is.
+        network_error = ProcessingError("SPARQL query failed: connection refused")
+        stub = _StubStoreBackend(triples=[], execute_sparql_error=network_error)
+        template = self._template()
+
+        with self.assertRaises(ProcessingError) as ctx:
+            execute_construct_template(template, {"value": "x"}, stub)
+
+        # The exact same exception instance propagates unchanged (not
+        # re-wrapped in a new ProcessingError with a different message).
+        self.assertIs(ctx.exception, network_error)
+
+    def test_execute_sparql_arbitrary_exception_type_also_propagates_unwrapped(self):
+        # Confirm this holds even for a non-ProcessingError exception type
+        # (e.g. a raw network library error) — execute_construct_template
+        # does not catch-and-wrap at all; add_triplets is simply never
+        # reached because execute_sparql raised first.
+        original_error = ConnectionError("simulated network failure")
+        stub = _StubStoreBackend(triples=[], execute_sparql_error=original_error)
+        template = self._template()
+
+        with self.assertRaises(ConnectionError) as ctx:
+            execute_construct_template(template, {"value": "x"}, stub)
+
+        self.assertIs(ctx.exception, original_error)
+        self.assertEqual(stub.add_triplets_calls, [])
+
+    # --- 6. target_graph precedence ---
+
+    def test_target_graph_argument_overrides_template_target_graph(self):
+        stub = _StubStoreBackend(triples=[])
+        template = self._template(target_graph="http://ex.org/graphs/template_default")
+
+        execute_construct_template(
+            template, {"value": "x"}, stub, target_graph="http://ex.org/graphs/explicit"
+        )
+
+        _, add_triplets_options = stub.add_triplets_calls[0]
+        self.assertEqual(add_triplets_options["graph"], "http://ex.org/graphs/explicit")
+
+    def test_template_target_graph_used_when_argument_is_none(self):
+        stub = _StubStoreBackend(triples=[])
+        template = self._template(target_graph="http://ex.org/graphs/template_default")
+
+        execute_construct_template(template, {"value": "x"}, stub, target_graph=None)
+
+        _, add_triplets_options = stub.add_triplets_calls[0]
+        self.assertEqual(add_triplets_options["graph"], "http://ex.org/graphs/template_default")
+
+    def test_no_target_graph_anywhere_passes_none_to_add_triplets(self):
+        stub = _StubStoreBackend(triples=[])
+        template = self._template(target_graph=None)
+
+        execute_construct_template(template, {"value": "x"}, stub)
+
+        _, add_triplets_options = stub.add_triplets_calls[0]
+        self.assertIsNone(add_triplets_options["graph"])
+
+    # --- 7. render_construct_template's ValidationError propagates unchanged ---
+
+    def test_missing_required_param_validation_error_propagates_unwrapped(self):
+        stub = _StubStoreBackend(triples=[])
+        template = self._template()
+
+        with self.assertRaises(ValidationError):
+            # Omit the required "value" parameter entirely.
+            execute_construct_template(template, {}, stub)
+
+        # Rendering must have failed before any query was attempted.
+        self.assertEqual(stub.execute_sparql_calls, [])
+        self.assertEqual(stub.add_triplets_calls, [])
+
+
+# ---------------------------------------------------------------------------
+# construct_template_step_handler: pipeline integration.
+# ---------------------------------------------------------------------------
+
+
+class TestConstructTemplateStepHandler(unittest.TestCase):
+    def _template(self):
+        return ConstructTemplate(
+            name="step_handler_template",
+            description="test",
+            construct_query=(
+                "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+                "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+            ),
+            parameters=[ParameterDescriptor(name="value", type="literal", required=True)],
+        )
+
+    def test_missing_store_backend_raises_processing_error(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(self._template())
+
+        with self.assertRaises(ProcessingError):
+            construct_template_step_handler(
+                None,
+                template_name="step_handler_template",
+                params={"value": "x"},
+                construct_template_registry=registry,
+                # store_backend deliberately omitted
+            )
+
+    def test_missing_registry_raises_processing_error(self):
+        stub = _StubStoreBackend(triples=[])
+
+        with self.assertRaises(ProcessingError):
+            construct_template_step_handler(
+                None,
+                template_name="step_handler_template",
+                params={"value": "x"},
+                store_backend=stub,
+                # construct_template_registry deliberately omitted
+            )
+
+    def test_unknown_template_name_raises_validation_error(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(self._template())
+        stub = _StubStoreBackend(triples=[])
+
+        with self.assertRaises(ValidationError):
+            construct_template_step_handler(
+                None,
+                template_name="does_not_exist",
+                params={"value": "x"},
+                store_backend=stub,
+                construct_template_registry=registry,
+            )
+
+    def test_happy_path_delegates_to_execute_construct_template(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(self._template())
+        fixed_triples = [("http://ex.org/s1", "http://ex.org/p1", "hello")]
+        stub = _StubStoreBackend(triples=fixed_triples)
+
+        result = construct_template_step_handler(
+            None,
+            template_name="step_handler_template",
+            params={"value": "hello"},
+            store_backend=stub,
+            construct_template_registry=registry,
+        )
+
+        self.assertEqual(
+            [(t.subject, t.predicate, t.object) for t in result],
+            fixed_triples,
+        )
+        self.assertEqual(len(stub.add_triplets_calls), 1)
+
+    def test_engine_config_fallback_used_when_options_omit_store_backend(self):
+        registry = ConstructTemplateRegistry()
+        registry.register(self._template())
+        stub = _StubStoreBackend(triples=[("http://ex.org/s1", "http://ex.org/p1", "v")])
+
+        result = construct_template_step_handler(
+            None,
+            template_name="step_handler_template",
+            params={"value": "v"},
+            engine_config={"store_backend": stub, "construct_template_registry": registry},
+        )
+
+        self.assertEqual(len(result), 1)
+
+
+class TestConstructTemplatePipelineIntegration(unittest.TestCase):
+    """
+    End-to-end: PipelineBuilder.add_step with the "construct_template" step
+    type -> ExecutionEngine.execute_pipeline with store_backend + registry
+    passed in -> triplets returned/persisted. Confirms Requirement 7.5 (no
+    PipelineStep/_execute_step changes needed) holds in practice.
+    """
+
+    def test_construct_template_step_executes_end_to_end_via_execution_engine(self):
+        from semantica.pipeline import ExecutionEngine, PipelineBuilder
+
+        registry = ConstructTemplateRegistry()
+        registry.register(
+            ConstructTemplate(
+                name="e2e_template",
+                description="test",
+                construct_query=(
+                    "CONSTRUCT { <http://ex.org/s1> <http://ex.org/p1> {{value}} } "
+                    "WHERE { <http://ex.org/s1> <http://ex.org/p1> {{value}} }"
+                ),
+                parameters=[ParameterDescriptor(name="value", type="literal", required=True)],
+            )
+        )
+        fixed_triples = [("http://ex.org/s1", "http://ex.org/p1", "Alice")]
+        stub = _StubStoreBackend(triples=fixed_triples)
+
+        builder = PipelineBuilder()
+        builder.add_step(
+            "apply_e2e_template",
+            "construct_template",
+            handler=construct_template_step_handler,
+            template_name="e2e_template",
+            params={"value": "Alice"},
+        )
+        pipeline = builder.build(name="e2e_pipeline")
+
+        engine = ExecutionEngine()
+        result = engine.execute_pipeline(
+            pipeline,
+            data=None,
+            store_backend=stub,
+            construct_template_registry=registry,
+        )
+
+        self.assertTrue(result.success, msg=f"Pipeline failed: {result.errors}")
+        returned_triplets = result.output
+        self.assertEqual(
+            [(t.subject, t.predicate, t.object) for t in returned_triplets],
+            fixed_triples,
+        )
+        # Confirm the triples were actually persisted via add_triplets.
+        self.assertEqual(len(stub.add_triplets_calls), 1)
+        persisted_triplets, _ = stub.add_triplets_calls[0]
+        self.assertEqual(
+            [(t.subject, t.predicate, t.object) for t in persisted_triplets],
+            fixed_triples,
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/triplet_store/test_query_engine.py

@@ -0,0 +1,97 @@
+"""
+Tests for semantica.triplet_store.query_engine, focused on the
+QueryResult.triples field added for CONSTRUCT query support.
+"""
+
+import os
+import sys
+import unittest
+from unittest.mock import MagicMock
+
+PROJECT_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", ".."))
+if PROJECT_ROOT not in sys.path:
+    sys.path.insert(0, PROJECT_ROOT)
+
+from semantica.triplet_store.query_engine import QueryEngine, QueryResult
+
+
+class TestQueryResultTriplesField(unittest.TestCase):
+    def test_query_result_triples_defaults_to_empty_list(self):
+        result = QueryResult(bindings=[], variables=[])
+        self.assertEqual(result.triples, [])
+
+    def test_query_result_triples_field_is_independent_per_instance(self):
+        # default_factory=list must produce a fresh list per instance, not a
+        # shared mutable default.
+        r1 = QueryResult(bindings=[], variables=[])
+        r2 = QueryResult(bindings=[], variables=[])
+        r1.triples.append(("s", "p", "o"))
+        self.assertEqual(r1.triples, [("s", "p", "o")])
+        self.assertEqual(r2.triples, [])
+
+    def test_query_result_accepts_explicit_triples(self):
+        triples = [("http://ex.org/s1", "http://ex.org/p1", "v1")]
+        result = QueryResult(bindings=[], variables=[], triples=triples)
+        self.assertEqual(result.triples, triples)
+
+
+class FakeConstructBackend:
+    """Fake store_backend whose execute_sparql returns a CONSTRUCT-shaped result."""
+
+    supports_named_graphs = True
+
+    def execute_sparql(self, query, **options):
+        return {
+            "success": True,
+            "bindings": [],
+            "variables": [],
+            "triples": [
+                ("http://ex.org/s1", "http://ex.org/p1", "v1"),
+                ("http://ex.org/s2", "http://ex.org/p2", "v2"),
+            ],
+            "metadata": {"query": query, "result_format": "construct"},
+        }
+
+
+class FakeBindingsBackend:
+    """Fake store_backend whose execute_sparql returns a plain bindings result
+    with no "triples" key at all, matching pre-CONSTRUCT-extension backends."""
+
+    supports_named_graphs = True
+
+    def execute_sparql(self, query, **options):
+        return {
+            "success": True,
+            "bindings": [{"s": {"value": "http://ex.org/s1"}}],
+            "variables": ["s"],
+            "metadata": {"query": query},
+        }
+
+
+class TestExecuteQueryPopulatesTriples(unittest.TestCase):
+    def test_execute_query_populates_triples_from_construct_backend(self):
+        engine = QueryEngine(enable_caching=False, enable_optimization=False)
+        result = engine.execute_query(
+            "CONSTRUCT { ?s ?p ?o } WHERE { ?s ?p ?o }", FakeConstructBackend()
+        )
+        self.assertEqual(
+            result.triples,
+            [
+                ("http://ex.org/s1", "http://ex.org/p1", "v1"),
+                ("http://ex.org/s2", "http://ex.org/p2", "v2"),
+            ],
+        )
+
+    def test_execute_query_defaults_triples_to_empty_list_when_backend_omits_key(self):
+        engine = QueryEngine(enable_caching=False, enable_optimization=False)
+        result = engine.execute_query(
+            "SELECT ?s WHERE { ?s ?p ?o }", FakeBindingsBackend()
+        )
+        self.assertEqual(result.triples, [])
+        # Non-CONSTRUCT behavior otherwise unaffected.
+        self.assertEqual(result.bindings, [{"s": {"value": "http://ex.org/s1"}}])
+        self.assertEqual(result.variables, ["s"])
+
+
+if __name__ == "__main__":
+    unittest.main()