feat: preserve RDF language tags and datatypes through ingestion and query (#1047)

Language tags and XSD datatypes on RDF literals were being silently
dropped at multiple points in the pipeline, making SPARQL FILTER(LANG())
queries and multilingual datasets non-functional.

Ingestion fixes:
- load_knowledge.py and load_turtle.py now extract .language and
  .datatype from rdflib Literal objects instead of discarding them
- Triple dataclass gains optional o_datatype and o_language fields
- _string_to_term() emits "dt" and "ln" in the wire format
- AsyncBulkClient uses the same term serialization as BulkClient

Query fix:
- TriplesClient.query_gen() preserves Term objects directly instead of
  converting through Uri/Literal (which are str subclasses with no room
  for language metadata), enabling SPARQL LANG() filters to work

trustgraph-base/trustgraph/api/async_bulk_client.py

@@ -4,6 +4,7 @@ import websockets
 from typing import Optional, AsyncIterator, Dict, Any, Iterator
 
 from . types import Triple
+from . bulk_client import _string_to_term
 
 
 class AsyncBulkClient:
@@ -45,9 +46,13 @@ class AsyncBulkClient:
         async with websockets.connect(ws_url, ping_interval=20, ping_timeout=self.timeout) as websocket:
             async for triple in triples:
                 message = {
-                    "s": triple.s,
-                    "p": triple.p,
-                    "o": triple.o
+                    "s": _string_to_term(triple.s),
+                    "p": _string_to_term(triple.p),
+                    "o": _string_to_term(
+                        triple.o,
+                        datatype=triple.o_datatype,
+                        language=triple.o_language,
+                    ),
                 }
                 await websocket.send(json.dumps(message))
 

trustgraph-base/trustgraph/api/bulk_client.py

@@ -15,13 +15,19 @@ from . types import Triple
 from . exceptions import ProtocolException
 
 
-def _string_to_term(value: str) -> Dict[str, Any]:
+def _string_to_term(
+    value: str, datatype: str = "", language: str = ""
+) -> Dict[str, Any]:
     """Convert a string value to Term format for the gateway."""
-    # Treat URIs as IRI type, otherwise as literal
     if value.startswith("http://") or value.startswith("https://") or "://" in value:
         return {"t": "i", "i": value}
     else:
-        return {"t": "l", "v": value}
+        result: Dict[str, Any] = {"t": "l", "v": value}
+        if datatype:
+            result["dt"] = datatype
+        if language:
+            result["ln"] = language
+        return result
 
 
 class BulkClient:
@@ -141,7 +147,11 @@ class BulkClient:
                 batch.append({
                     "s": _string_to_term(triple.s),
                     "p": _string_to_term(triple.p),
-                    "o": _string_to_term(triple.o)
+                    "o": _string_to_term(
+                        triple.o,
+                        datatype=triple.o_datatype,
+                        language=triple.o_language,
+                    ),
                 })
                 if len(batch) >= batch_size:
                     message = {

trustgraph-base/trustgraph/api/types.py

@@ -19,10 +19,14 @@ class Triple:
         s: Subject (entity URI or value)
         p: Predicate (relationship URI)
         o: Object (entity URI, literal value, or typed value)
+        o_datatype: XSD datatype URI for literal objects (e.g. "xsd:string")
+        o_language: Language tag for literal objects (e.g. "en", "lt")
     """
     s : str
     p : str
     o : str
+    o_datatype : str = ""
+    o_language : str = ""
 
 @dataclasses.dataclass
 class ConfigKey:

trustgraph-base/trustgraph/base/triples_client.py

@@ -58,7 +58,7 @@ class TriplesClient(RequestResponse):
                 raise RuntimeError(resp.error.message)
 
             batch = [
-                Triple(to_value(v.s), to_value(v.p), to_value(v.o))
+                Triple(v.s, v.p, v.o)
                 for v in resp.triples
             ]
             await queue.put(batch)