fix(export): normalize entity name to label on all RDF paths

convert_kg_to_rdf() maps an entity's 'name' to 'label'/'text' but was
never invoked from export_to_rdf(), so graphs produced by GraphBuilder
(which emit 'name') exported with an empty semantica:text on every RDF
format (turtle, ntriples, rdfxml, jsonld). Call convert_kg_to_rdf() at
the export boundary before validation/serialization so all formats
benefit from a single normalization step.

Add regression tests asserting a name-only entity exports a non-empty
label across all four serializers and the file-writing entry point,
plus that an explicit 'text' is not clobbered and an id tail is used
as a fallback label.

Closes #1097

semantica/export/rdf_exporter.py

@@ -1054,6 +1054,12 @@ class RDFExporter:
 
             self.logger.debug(f"Exporting to RDF format: {format}")
 
+            # Normalize the graph before serialization so every format benefits
+            # from field normalization (e.g. mapping 'name' -> 'label'/'text').
+            # Without this, graphs produced by GraphBuilder (which emit 'name')
+            # export with an empty semantica:text on all RDF paths. See #1097.
+            data = self.serializer.convert_kg_to_rdf(data)
+
             self.progress_tracker.update_tracking(
                 tracking_id, message="Validating RDF data..."
             )

tests/export/test_rdf_exporter.py

@@ -3,7 +3,6 @@
 import pytest
 from semantica.export import RDFExporter
 
-
 RDF_DATA = {
     "entities": [
         {"id": "e1", "text": "Apple Inc.", "type": "ORG", "confidence": 0.95},
@@ -89,3 +88,74 @@ def test_validate_rdf_returns_overall_valid_key(exporter):
     result = exporter.validate_rdf(RDF_DATA)
     assert "overall_valid" in result
     assert isinstance(result["overall_valid"], bool)
+
+
+# --- Regression tests for #1097 -------------------------------------------
+# convert_kg_to_rdf() normalizes an entity's 'name' into 'label'/'text' but was
+# never called from the export path, so GraphBuilder graphs (which emit 'name')
+# exported with an empty semantica:text on every RDF format. These tests assert
+# the human-readable label survives export on all four serializers.
+
+NAME_ONLY_DATA = {
+    "entities": [
+        {
+            "id": "https://example.org/acme",
+            "name": "Acme Corp",
+            "type": "https://example.org/Org",
+            "confidence": 0.91,
+        },
+    ],
+    "relationships": [],
+}
+
+
+@pytest.mark.parametrize("fmt", ["turtle", "ntriples", "rdfxml", "jsonld"])
+def test_name_only_entity_exports_nonempty_label(exporter, fmt):
+    """A GraphBuilder-style 'name'-only entity must export a non-empty label.
+
+    Regression for #1097: previously every RDF path dropped the label because
+    convert_kg_to_rdf() was never invoked from export_to_rdf().
+    """
+    result = exporter.export_to_rdf(NAME_ONLY_DATA, format=fmt)
+    assert "Acme Corp" in result
+    # The empty-text pattern that the bug produced must not appear.
+    assert 'semantica:text ""' not in result
+
+
+def test_name_only_export_to_file_contains_label(exporter, tmp_path):
+    """The file-writing entry point must also normalize name -> label (#1097)."""
+    out = tmp_path / "acme.ttl"
+    exporter.export(NAME_ONLY_DATA, str(out), format="turtle")
+    content = out.read_text()
+    assert "Acme Corp" in content
+    assert 'semantica:text ""' not in content
+
+
+def test_existing_text_not_overwritten_by_name(exporter):
+    """An entity that already has 'text' must keep it, not be clobbered by 'name' (#1097)."""
+    data = {
+        "entities": [
+            {
+                "id": "https://example.org/acme",
+                "name": "Acme Corp",
+                "text": "Explicit Text",
+                "type": "https://example.org/Org",
+            }
+        ],
+        "relationships": [],
+    }
+    result = exporter.export_to_rdf(data, format="turtle")
+    assert "Explicit Text" in result
+    assert "Acme Corp" not in result
+
+
+def test_id_fallback_label_when_no_name(exporter):
+    """With neither 'name' nor 'text', the id tail is used as the label (#1097)."""
+    data = {
+        "entities": [
+            {"id": "https://example.org/acme", "type": "https://example.org/Org"}
+        ],
+        "relationships": [],
+    }
+    result = exporter.export_to_rdf(data, format="turtle")
+    assert 'semantica:text ""' not in result