Complete UsdShade NodeDef source queries

ROADMAP.md

@@ -183,7 +183,7 @@ Features from the C++ reference implementation not covered by the core specifica
 | Parallelism (Rayon) | :construction: | | Composition graph is `&`-only, ready for parallel execution |
 | [Incremental invalidation](https://openusd.org/release/api/class_pcp_changes.html) | :white_check_mark: | `0.6.0` | `pcp::Changes` classifies each `sdf::ChangeList` into tiered invalidations scoped by the reverse dependency map (`pcp::Dependencies`), so an edit drops only the affected indices<br>Remaining — per-prim composition revision; `query_errors` compute-once; spec-stack-refresh splice |
 | [UsdGeom](https://openusd.org/release/api/usd_geom_page_front.html) (geometry, transforms, cameras) | :white_check_mark: | `0.4.0` | Trait-views behind `geom` (the `SchemaBase → … → Curves` chain, read + author): all intrinsic shapes, Camera, Xform/Scope, Mesh + GeomSubset, curve/point/patch types, PointInstancer; full `xformOpOrder` evaluator<br>Remaining — PrimvarsAPI / ModelAPI / MotionAPI / VisibilityAPI / BBoxCache / XformCache |
-| [UsdShade](https://openusd.org/release/api/usd_shade_page_front.html) (materials, shaders) | :white_check_mark: | `0.5.0` | Trait-views behind `shade` (read + author): `Connectable`, `Input`, `Output`, `ConnectionTarget`, `ConnectedSources`, `ShadingAttribute`, `ProducerFilter`, `ResolvedTerminal`, `InterfaceInputConsumersMap`, Shader / NodeGraph / Material, MaterialBindingAPI, and the UsdPreviewSurface reader<br>Remaining — Material base-material; `CoordSysAPI`; renderer shader dialects (MDL / MaterialX) |
+| [UsdShade](https://openusd.org/release/api/usd_shade_page_front.html) (materials, shaders) | :white_check_mark: | `0.5.0` | Trait-views behind `shade` (read + author): `Connectable`, `Input`, `Output`, `ConnectionTarget`, `ConnectedSources`, `ShadingAttribute`, `ProducerFilter`, `ResolvedTerminal`, `InterfaceInputConsumersMap`, `ImplementationSource`, `SdrMetadata`, Shader / NodeGraph / Material, MaterialBindingAPI, and the UsdPreviewSurface reader<br>Remaining — Material base-material; `CoordSysAPI`; renderer shader dialects (MDL / MaterialX) |
 | [UsdLux](https://openusd.org/release/api/usd_lux_page_front.html) (lighting) | :white_check_mark: | `0.4.0` | Trait-views behind `lux` feature (built on the `geom` chain — lights are `Xformable` / `Boundable` prims plus the `Light` interface, with read + author on the same handle): all 8 concrete light prims + LightFilter, and the applied LightAPI / ShapingAPI / ShadowAPI / LightListAPI |
 | [UsdSkel](https://openusd.org/release/api/usd_skel_page_front.html) (skeletons, skinning) | :white_check_mark: | `0.5.0` | Trait-views behind `skel` (read + author; `skel = ["geom"]`): SkelRoot / Skeleton as `Boundable`, SkelAnimation / BlendShape (incl. inbetween shapes), namespace-inherited SkelBindingAPI — plus the object model (Topology, AnimMapper, SkeletonResolver, SkinningResolver, SkelAnimQuery, `discover_bindings`, pure-math LBS / blend shapes)<br>Remaining — stage-level interpolation of SkelAnimation time samples |
 | [UsdVol](https://openusd.org/release/api/usd_vol_page_front.html) (volumes) | :white_check_mark: | `0.5.0` | Trait-views behind `vol` feature (built on the `geom` chain): `Volume` (a `Gprim` with `field:<name>` relationships) and the file-backed `OpenVDBAsset` / `Field3DAsset` (the shared `FieldAsset` attrs)<br>Remaining — the `ParticleField*` Gaussian-splat schemas |

src/schemas/shade/mod.rs

@@ -29,6 +29,9 @@
 //! as far as [`ProducerFilter`] admits. [`NodeGraphInterface`] maps interface
 //! inputs in the reverse direction to their consumers. Specialized consumers
 //! include [`Material::compute_surface_source`] and [`read_preview_surface`].
+//! [`Shader::implementation_source`] and the source queries interpret the
+//! active `NodeDef` implementation family, while [`SdrMetadata`] exposes the
+//! composed shader-registry metadata on shaders, inputs, and outputs.
 //! To find every shading prim on a stage, traverse it and gate each prim
 //! through the typed `get` (e.g. [`Material::get`]), mirroring C++
 //! `prim.IsA<UsdShadeMaterial>()`.
@@ -63,6 +66,7 @@ mod binding;
 mod connectable;
 mod input;
 mod interface;
+mod node_def;
 mod output;
 mod preview;
 mod schema;
@@ -76,6 +80,7 @@ pub use connectable::{
 };
 pub use input::Input;
 pub use interface::{InterfaceInputConsumersMap, NodeGraphInterface};
+pub use node_def::SdrMetadata;
 pub use output::Output;
 pub use preview::{Channel, ReadPreviewSurface, read_preview_surface};
 pub use schema::{Material, NodeGraph, ResolvedTerminal, Shader, TerminalKind, TerminalSource};