Reduction and aggregation operators lead their names, and five measurement-destination loci are registered

imas_standard_names/grammar/ir.py

@@ -172,6 +172,7 @@ class LocusType(StrEnum):
         "per_toroidal_and_poloidal_mode_number",
         "per_toroidal_mode",
         "perturbed",
+        "root_mean_square",
         "surface_integrated",
         "time_averaged",
         "volume_averaged",

imas_standard_names/grammar/model_types.py

@@ -600,6 +600,11 @@ class Position(StrEnum):
     RECTANGLE_CENTER = "rectangle_center"
     ANNULUS_CENTER = "annulus_center"
     ARC_OF_CIRCLE_CENTER = "arc_of_circle_center"
+    REFLECTOMETER_CUTOFF_POSITION = "reflectometer_cutoff_position"
+    CHARGE_EXCHANGE_CHANNEL = "charge_exchange_channel"
+    THOMSON_SCATTERING_CHANNEL_POSITION = "thomson_scattering_channel_position"
+    LANGMUIR_PROBE_POSITION = "langmuir_probe_position"
+    CALORIMETRY_COMPONENT = "calorimetry_component"
     ACTIVE_SPATIAL_RESOLUTION_ZONE = "active_spatial_resolution_zone"
     ACTIVE_WALL_POINT = "active_wall_point"
     BEAM_PATH = "beam_path"

imas_standard_names/grammar/parser.py

@@ -675,6 +675,7 @@ def _peel_outer_operator(
         for name, meta in v.operators.items()
         if meta.get("kind") == OperatorKind.BINARY.value
     }
+    reductions = _reduction_prefix_operators(v)
 
     # a) unary postfix: s ends with "_<op>", longest op first. A postfix at the
     # tail of an explicit prefix or binary form belongs to that operator's
@@ -701,8 +702,17 @@ def _peel_outer_operator(
     if prefix_match is not None:
         new_s = s[len(prefix_match) + len("_of_") :]
         if new_s:
+            # A _of_-authored domain reduction converges on the bare leading
+            # spelling: the reduction collapses the whole operand, so the
+            # joiner would state the same scope under a second canonical
+            # string. Carry the bare flag so every spelling of one quantity
+            # shares a single representation and one canonical form.
             return (
-                OperatorApplication(kind=OperatorKind.UNARY_PREFIX, op=prefix_match),
+                OperatorApplication(
+                    kind=OperatorKind.UNARY_PREFIX,
+                    op=prefix_match,
+                    bare_prefix=prefix_match in reductions,
+                ),
                 new_s,
                 [],
             )

imas_standard_names/grammar/render.py

@@ -299,14 +299,31 @@ def _has_repositioning_tail(ir: StandardNameIR) -> bool:
     return ir.locus is not None and ir.locus.relation.value in {"of", "at"}
 
 
+# The accumulation family (accumulated, cumulative, cumulative_inside_flux_surface)
+# are bare-prefix tokens that modify the quantity as a whole and lead their name.
+# They are NOT relocated between base and locus the way a joiner-taking operator
+# is: the relocated spelling (``neutral_count_accumulated_at_wall``) would fold
+# the aggregation into the base group and contradict the leading canonical form.
+# Sibling reductions already lead via the operator stack; these stay qualifiers
+# and simply keep their leading seat, so ``_leading_bare_operators`` must not
+# extract them into the relocatable operator-qualifier bucket.
+_ACCUMULATION_LEADING_QUALIFIERS: frozenset[str] = frozenset(
+    {"accumulated", "cumulative", "cumulative_inside_flux_surface"}
+)
+
+
 def _leading_bare_operators(
     ir: StandardNameIR,
 ) -> tuple[list[Qualifier], list[Qualifier]]:
     """Split leading bare operators from ordinary base qualifiers."""
 
     operator_qualifiers: list[Qualifier] = []
     ordinary_qualifiers = list(ir.qualifiers)
-    while ordinary_qualifiers and ordinary_qualifiers[0].token in BARE_PREFIX_OPERATORS:
+    while (
+        ordinary_qualifiers
+        and ordinary_qualifiers[0].token in BARE_PREFIX_OPERATORS
+        and ordinary_qualifiers[0].token not in _ACCUMULATION_LEADING_QUALIFIERS
+    ):
         operator_qualifiers.append(ordinary_qualifiers.pop(0))
     return operator_qualifiers, ordinary_qualifiers
 

imas_standard_names/grammar/vocabularies/locus_registry.yml

@@ -646,7 +646,10 @@ loci:
   measurement_position:
     type: position
     allowed_relations: [at, of]
-    definition: The spatial location identified as the measurement position in the relevant plasma, diagnostic, or plant context.
+    definition: >-
+      The position in the cylindrical frame at which a diagnostic channel
+      samples, used for the coordinates of that position where the coordinate
+      serves many instrument families.
   midplane:
     type: position
     allowed_relations: [at, of]
@@ -842,6 +845,45 @@ loci:
     allowed_relations: [at, of]
     definition: The center of curvature of a circular arc.
 
+  # ── diagnostic measurement-destination loci ─────────────────────────
+  # Per-instrument sampling positions: the locations at which individual
+  # diagnostic channels measure. Distinct from the generic
+  # measurement_position locus, which survives only for the shared coordinate
+  # triple that many instrument families evaluate; a quantity whose
+  # instrument is known carries that instrument's own locus instead. Each
+  # accepts both _of_ (a claim about the location as an object) and _at_
+  # (a field value evaluated there).
+  reflectometer_cutoff_position:
+    type: position
+    allowed_relations: [of, at]
+    definition: >-
+      The plasma layer at which a reflectometer channel samples: where the
+      probing frequency meets the local cutoff, or for Doppler reflectometry
+      the backscatter resonance condition.
+  charge_exchange_channel:
+    type: position
+    allowed_relations: [of, at]
+    definition: >-
+      The sample volume of a charge-exchange recombination spectroscopy
+      channel, where beam-induced charge-exchange emission is collected.
+  thomson_scattering_channel_position:
+    type: position
+    allowed_relations: [of, at]
+    definition: The scattering volume assigned to one Thomson-scattering channel.
+  langmuir_probe_position:
+    type: position
+    allowed_relations: [of, at]
+    definition: >-
+      The location at which a Langmuir probe tip samples the local plasma,
+      embedded or reciprocating. Distinct from langmuir_probe, the probe
+      itself as an entity.
+  calorimetry_component:
+    type: position
+    allowed_relations: [of, at]
+    definition: >-
+      A discrete element of a calorimetry group whose extracted thermal
+      energy and power are measured.
+
   # ====================================================================
   # Geometry-typed loci (shape/region boundary: _at_, _of_, _over_)
   # ====================================================================

tests/grammar/test_reduction_over_binary.py

@@ -217,6 +217,7 @@ def test_every_flux_surface_reduction_wraps_a_binary_form(reduction: str) -> Non
         "volume_averaged",
         "line_averaged",
         "time_averaged",
+        "root_mean_square",
         "normalized",
         "perturbed",
         "change_in",
@@ -225,7 +226,6 @@ def test_every_flux_surface_reduction_wraps_a_binary_form(reduction: str) -> Non
         "inverse_of",
         "time_derivative_of",
         "maximum_of",
-        "root_mean_square_of",
     ],
 )
 def test_no_other_transformation_wraps_a_binary_form(prefix: str) -> None:

tests/grammar/test_render_canonical.py

@@ -329,9 +329,7 @@ def test_render_mechanism_with_locus() -> None:
 def test_render_operator_between_projected_base_and_locus() -> None:
     """Render ``<axis>_<qual>_<base>_<op>_<locus>`` canonically."""
     ir = StandardNameIR(
-        operators=[
-            OperatorApplication(kind=OperatorKind.UNARY_PREFIX, op="root_mean_square")
-        ],
+        operators=[OperatorApplication(kind=OperatorKind.UNARY_PREFIX, op="maximum")],
         projection=AxisProjection(axis="radial", shape=ProjectionShape.COMPONENT),
         qualifiers=[Qualifier(token="electron")],
         base=QuantityOrCarrier(token="pressure", kind=BaseKind.QUANTITY),
@@ -341,9 +339,7 @@ def test_render_operator_between_projected_base_and_locus() -> None:
             type=LocusType.POSITION,
         ),
     )
-    assert compose(ir) == (
-        "radial_electron_pressure_root_mean_square_at_plasma_boundary"
-    )
+    assert compose(ir) == ("radial_electron_pressure_maximum_at_plasma_boundary")
 
 
 def test_render_nested_operators_outer_first() -> None:

tests/grammar/test_round_trip.py

@@ -1,4 +1,4 @@
-"""Round-trip test battery for grammar (plan 38 §A10, item 1).
+"""Round-trip test battery for the grammar compose invariant.
 
 Synthesises ≥ 5 000 valid IR instances via seeded random, composes each to
 a canonical string, parses the string back, and asserts the re-parsed IR is
@@ -40,6 +40,7 @@
 )
 from imas_standard_names.grammar.parser import (
     Vocabularies,
+    _reduction_prefix_operators,
     load_default_vocabularies,
     parse,
 )
@@ -138,7 +139,16 @@ def _make_base_ir(
 
 
 def _prefix_op(op: str) -> OperatorApplication:
-    return OperatorApplication(kind=OperatorKind.UNARY_PREFIX, op=op)
+    """Build a canonical prefix application.
+
+    A domain reduction carries the bare flag (``flux_surface_averaged_<x>``),
+    so its composed spelling re-parses to the same IR; every other prefix
+    operator keeps the ``_of_`` joiner and the default bare_prefix=False.
+    """
+    reductions = _reduction_prefix_operators(load_default_vocabularies())
+    return OperatorApplication(
+        kind=OperatorKind.UNARY_PREFIX, op=op, bare_prefix=op in reductions
+    )
 
 
 def _postfix_op(op: str) -> OperatorApplication:
@@ -484,7 +494,7 @@ def test_round_trip_mechanisms(vocabs: Vocabularies) -> None:
 def test_round_trip_combined_large(vocabs: Vocabularies) -> None:
     """Combinatorial sweep targeting ≥ 5 000 unique IR instances.
 
-    Validates that the A10 target of 5 000 synthetic round-trips is met.
+    Validates that 5 000 synthetic round-trips are exercised.
     Uses a seeded RNG for reproducibility.
     """
     rng = random.Random(1234)

tests/grammar/test_tail_gated_operator_order.py

@@ -9,10 +9,6 @@
 @pytest.mark.parametrize(
     ("current", "canonical"),
     [
-        (
-            "root_mean_square_of_wave_current_of_antenna_strap",
-            "wave_current_root_mean_square_of_antenna_strap",
-        ),
         (
             "voltage_of_ion_cyclotron_heating_antenna_amplitude",
             "voltage_amplitude_of_ion_cyclotron_heating_antenna",
@@ -61,10 +57,6 @@
             "maximum_of_inverse_of_electron_density_at_magnetic_axis",
             "electron_density_inverse_maximum_at_magnetic_axis",
         ),
-        (
-            "root_mean_square_of_radial_electron_pressure_at_plasma_boundary",
-            "radial_electron_pressure_root_mean_square_at_plasma_boundary",
-        ),
         (
             "maximum_of_derivative_of_pressure_at_pedestal",
             "pressure_derivative_maximum_at_pedestal",
@@ -98,6 +90,14 @@ def test_tailed_operator_moves_between_base_and_locus(
             "toroidal_argon_velocity_flux_surface_averaged_at_plasma_boundary",
             "flux_surface_averaged_toroidal_argon_velocity_at_plasma_boundary",
         ),
+        (
+            "wave_current_root_mean_square_of_antenna_strap",
+            "root_mean_square_wave_current_of_antenna_strap",
+        ),
+        (
+            "radial_electron_pressure_root_mean_square_at_plasma_boundary",
+            "root_mean_square_radial_electron_pressure_at_plasma_boundary",
+        ),
     ],
 )
 def test_bare_operator_leads_instead_of_moving_before_the_locus(
@@ -111,6 +111,36 @@ def test_bare_operator_leads_instead_of_moving_before_the_locus(
     assert canonical in str(rejection.value)
 
 
+@pytest.mark.parametrize(
+    ("authored", "canonical"),
+    [
+        (
+            "root_mean_square_of_wave_current_of_antenna_strap",
+            "root_mean_square_wave_current_of_antenna_strap",
+        ),
+        (
+            "spectral_width_root_mean_square_of_spectrometer_channel",
+            "root_mean_square_spectral_width_of_spectrometer_channel",
+        ),
+    ],
+)
+def test_reduction_of_form_converges_on_the_leading_spelling(
+    authored: str, canonical: str
+) -> None:
+    """An ``_of_``-authored domain reduction renders to the bare leading form.
+
+    root_mean_square is a precedence-30 reduction: it collapses the whole
+    operand, so the joiner states the same scope under a second string. The
+    authored ``_of_`` spelling must share one representation with the canonical
+    bare form and draw the same rendered string.
+    """
+    ir = parse(authored).ir
+    assert parse(canonical, strict=True).ir == ir
+    assert compose(ir) == canonical
+    with pytest.raises(ValueError):
+        parse(authored, strict=True)
+
+
 def test_an_outer_operator_cannot_move_past_a_leading_reduction() -> None:
     """A joiner-taking operator stays put when a reduction leads its operand.
 

tests/name_schema/test_reductions.py

@@ -33,7 +33,7 @@ def test_rms_reduction_scalar():
         {
             "kind": "scalar",
             "physics_domain": "core_plasma_physics",
-            "name": "root_mean_square_of_electron_temperature",
+            "name": "root_mean_square_electron_temperature",
             "description": "RMS",
             "documentation": "Root mean square of electron temperature.",
             "unit": "eV",