diff --git a/.gitignore b/.gitignore
index 3b0fc39..1470b8c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -159,4 +159,6 @@ cython_debug/
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
 .pdm-python
-ndarray.pyi
\ No newline at end of file
+ndarray.pyi
+
+prof/
\ No newline at end of file
diff --git a/docs/api/validation/dtype.md b/docs/api/validation/dtype.md
new file mode 100644
index 0000000..fd599ca
--- /dev/null
+++ b/docs/api/validation/dtype.md
@@ -0,0 +1,7 @@
+# dtype
+
+```{eval-rst}
+.. automodule:: numpydantic.validation.dtype
+    :members:
+    :undoc-members:
+```
\ No newline at end of file
diff --git a/docs/api/validation/index.md b/docs/api/validation/index.md
new file mode 100644
index 0000000..d0f5a11
--- /dev/null
+++ b/docs/api/validation/index.md
@@ -0,0 +1,6 @@
+# validation
+
+```{toctree}
+dtype
+shape
+```
\ No newline at end of file
diff --git a/docs/api/shape.md b/docs/api/validation/shape.md
similarity index 54%
rename from docs/api/shape.md
rename to docs/api/validation/shape.md
index 4c8638c..60a7a19 100644
--- a/docs/api/shape.md
+++ b/docs/api/validation/shape.md
@@ -1,7 +1,7 @@
 # shape
 
 ```{eval-rst}
-.. automodule:: numpydantic.shape
+.. automodule:: numpydantic.validation.shape
     :members:
     :undoc-members:
 ```
\ No newline at end of file
diff --git a/docs/index.md b/docs/index.md
index 0880a59..9caaaf7 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -484,13 +484,13 @@ interfaces
 
 api/index
 api/interface/index
+api/validation/index
 api/dtype
 api/ndarray
 api/maps
 api/meta
 api/schema
 api/serialization
-api/shape
 api/types
 
 ```
diff --git a/src/numpydantic/__init__.py b/src/numpydantic/__init__.py
index 803d8d2..98b8bd1 100644
--- a/src/numpydantic/__init__.py
+++ b/src/numpydantic/__init__.py
@@ -4,7 +4,7 @@
 
 from numpydantic.ndarray import NDArray
 from numpydantic.meta import update_ndarray_stub
-from numpydantic.shape import Shape
+from numpydantic.validation.shape import Shape
 
 update_ndarray_stub()
 
diff --git a/src/numpydantic/dtype.py b/src/numpydantic/dtype.py
index 12d766a..84b28cc 100644
--- a/src/numpydantic/dtype.py
+++ b/src/numpydantic/dtype.py
@@ -12,6 +12,9 @@ module, rather than needing to import each individually.
 Some types like `Integer` are compound types - tuples of multiple dtypes.
 Check these using ``in`` rather than ``==``. This interface will develop in future
 versions to allow a single dtype check.
+
+For internal helper functions for validating dtype, 
+see :mod:`numpydantic.validation.dtype`
 """
 
 import sys
diff --git a/src/numpydantic/interface/dask.py b/src/numpydantic/interface/dask.py
index cd36a65..95d0619 100644
--- a/src/numpydantic/interface/dask.py
+++ b/src/numpydantic/interface/dask.py
@@ -33,11 +33,11 @@ class DaskJsonDict(JsonDict):
     name: str
     chunks: Iterable[tuple[int, ...]]
     dtype: str
-    array: list
+    value: list
 
     def to_array_input(self) -> DaskArray:
         """Construct a dask array"""
-        np_array = np.array(self.array, dtype=self.dtype)
+        np_array = np.array(self.value, dtype=self.dtype)
         array = from_array(
             np_array,
             name=self.name,
@@ -100,7 +100,7 @@ class DaskInterface(Interface):
         if info.round_trip:
             as_json = DaskJsonDict(
                 type=cls.name,
-                array=as_json,
+                value=as_json,
                 name=array.name,
                 chunks=array.chunks,
                 dtype=str(np_array.dtype),
diff --git a/src/numpydantic/interface/interface.py b/src/numpydantic/interface/interface.py
index bee85b6..42bb891 100644
--- a/src/numpydantic/interface/interface.py
+++ b/src/numpydantic/interface/interface.py
@@ -20,8 +20,8 @@ from numpydantic.exceptions import (
     ShapeError,
     TooManyMatchesError,
 )
-from numpydantic.shape import check_shape
 from numpydantic.types import DtypeType, NDArrayType, ShapeType
+from numpydantic.validation import validate_dtype, validate_shape
 
 T = TypeVar("T", bound=NDArrayType)
 U = TypeVar("U", bound="JsonDict")
@@ -76,6 +76,21 @@ class InterfaceMark(BaseModel):
 class JsonDict(BaseModel):
     """
     Representation of array when dumped with round_trip == True.
+
+    .. admonition:: Developer's Note
+
+        Any JsonDict that contains an actual array should be named ``value``
+        rather than array (or any other name), and nothing but the
+        array data should be named ``value`` .
+
+        During JSON serialization, it becomes ambiguous what contains an array
+        of data vs. an array of metadata. For the moment we would like to
+        reserve the ability to have lists of metadata, so until we rule that out,
+        we would like to be able to avoid iterating over every element of an array
+        in any context parameter transformation like relativizing/absolutizing paths.
+        To avoid that, it's good to agree on a single value name -- ``value`` --
+        and avoid using it for anything else.
+
     """
 
     type: str
@@ -274,25 +289,7 @@ class Interface(ABC, Generic[T]):
         Validate the dtype of the given array, returning
         ``True`` if valid, ``False`` if not.
         """
-        if self.dtype is Any:
-            return True
-
-        if isinstance(self.dtype, tuple):
-            valid = dtype in self.dtype
-        elif self.dtype is np.str_:
-            valid = getattr(dtype, "type", None) in (np.str_, str) or dtype in (
-                np.str_,
-                str,
-            )
-        else:
-            # try to match as any subclass, if self.dtype is a class
-            try:
-                valid = issubclass(dtype, self.dtype)
-            except TypeError:
-                # expected, if dtype or self.dtype is not a class
-                valid = dtype == self.dtype
-
-        return valid
+        return validate_dtype(dtype, self.dtype)
 
     def raise_for_dtype(self, valid: bool, dtype: DtypeType) -> None:
         """
@@ -326,7 +323,7 @@ class Interface(ABC, Generic[T]):
         if self.shape is Any:
             return True
 
-        return check_shape(shape, self.shape)
+        return validate_shape(shape, self.shape)
 
     def raise_for_shape(self, valid: bool, shape: Tuple[int, ...]) -> None:
         """
diff --git a/src/numpydantic/interface/numpy.py b/src/numpydantic/interface/numpy.py
index ad97474..6c84232 100644
--- a/src/numpydantic/interface/numpy.py
+++ b/src/numpydantic/interface/numpy.py
@@ -27,13 +27,13 @@ class NumpyJsonDict(JsonDict):
 
     type: Literal["numpy"]
     dtype: str
-    array: list
+    value: list
 
     def to_array_input(self) -> ndarray:
         """
         Construct a numpy array
         """
-        return np.array(self.array, dtype=self.dtype)
+        return np.array(self.value, dtype=self.dtype)
 
 
 class NumpyInterface(Interface):
@@ -99,6 +99,6 @@ class NumpyInterface(Interface):
 
         if info.round_trip:
             json_array = NumpyJsonDict(
-                type=cls.name, dtype=str(array.dtype), array=json_array
+                type=cls.name, dtype=str(array.dtype), value=json_array
             )
         return json_array
diff --git a/src/numpydantic/interface/zarr.py b/src/numpydantic/interface/zarr.py
index 41cad03..5dc647e 100644
--- a/src/numpydantic/interface/zarr.py
+++ b/src/numpydantic/interface/zarr.py
@@ -63,7 +63,7 @@ class ZarrJsonDict(JsonDict):
     type: Literal["zarr"]
     file: Optional[str] = None
     path: Optional[str] = None
-    array: Optional[list] = None
+    value: Optional[list] = None
 
     def to_array_input(self) -> Union[ZarrArray, ZarrArrayPath]:
         """
@@ -73,7 +73,7 @@ class ZarrJsonDict(JsonDict):
         if self.file:
             array = ZarrArrayPath(file=self.file, path=self.path)
         else:
-            array = zarr.array(self.array)
+            array = zarr.array(self.value)
         return array
 
 
@@ -202,7 +202,7 @@ class ZarrInterface(Interface):
             as_json["info"]["hexdigest"] = array.hexdigest()
 
             if dump_array or not is_file:
-                as_json["array"] = array[:].tolist()
+                as_json["value"] = array[:].tolist()
 
             as_json = ZarrJsonDict(**as_json)
         else:
diff --git a/src/numpydantic/ndarray.py b/src/numpydantic/ndarray.py
index fb81f69..6969d44 100644
--- a/src/numpydantic/ndarray.py
+++ b/src/numpydantic/ndarray.py
@@ -13,7 +13,7 @@ Extension of nptyping NDArray for pydantic that allows for JSON-Schema serializa
 
 """
 
-from typing import TYPE_CHECKING, Any, Tuple
+from typing import TYPE_CHECKING, Any, Literal, Tuple, get_origin
 
 import numpy as np
 from pydantic import GetJsonSchemaHandler
@@ -29,6 +29,7 @@ from numpydantic.schema import (
 )
 from numpydantic.serialization import jsonize_array
 from numpydantic.types import DtypeType, NDArrayType, ShapeType
+from numpydantic.validation.dtype import is_union
 from numpydantic.vendor.nptyping.error import InvalidArgumentsError
 from numpydantic.vendor.nptyping.ndarray import NDArrayMeta as _NDArrayMeta
 from numpydantic.vendor.nptyping.nptyping_type import NPTypingType
@@ -86,11 +87,18 @@ class NDArrayMeta(_NDArrayMeta, implementation="NDArray"):
         except InterfaceError:
             return False
 
+    def _is_literal_like(cls, item: Any) -> bool:
+        """
+        Changes from nptyping:
+        - doesn't just ducktype for literal but actually, yno, checks for being literal
+        """
+        return get_origin(item) is Literal
+
     def _get_shape(cls, dtype_candidate: Any) -> "Shape":
         """
         Override of base method to use our local definition of shape
         """
-        from numpydantic.shape import Shape
+        from numpydantic.validation.shape import Shape
 
         if dtype_candidate is Any or dtype_candidate is Shape:
             shape = Any
@@ -120,7 +128,7 @@ class NDArrayMeta(_NDArrayMeta, implementation="NDArray"):
 
         if dtype_candidate is Any:
             dtype = Any
-        elif is_dtype:
+        elif is_dtype or is_union(dtype_candidate):
             dtype = dtype_candidate
         elif issubclass(dtype_candidate, Structure):  # pragma: no cover
             dtype = dtype_candidate
diff --git a/src/numpydantic/schema.py b/src/numpydantic/schema.py
index cafa1f4..bfea3aa 100644
--- a/src/numpydantic/schema.py
+++ b/src/numpydantic/schema.py
@@ -5,7 +5,7 @@ Helper functions for use with :class:`~numpydantic.NDArray` - see the note in
 
 import hashlib
 import json
-from typing import TYPE_CHECKING, Any, Callable, Optional
+from typing import TYPE_CHECKING, Any, Callable, Optional, get_args
 
 import numpy as np
 from pydantic import BaseModel
@@ -16,6 +16,7 @@ from numpydantic import dtype as dt
 from numpydantic.interface import Interface
 from numpydantic.maps import np_to_python
 from numpydantic.types import DtypeType, NDArrayType, ShapeType
+from numpydantic.validation.dtype import is_union
 from numpydantic.vendor.nptyping.structure import StructureMeta
 
 if TYPE_CHECKING:  # pragma: no cover
@@ -51,7 +52,6 @@ def _lol_dtype(
     """Get the innermost dtype schema to use in the generated pydantic schema"""
     if isinstance(dtype, StructureMeta):  # pragma: no cover
         raise NotImplementedError("Structured dtypes are currently unsupported")
-
     if isinstance(dtype, tuple):
         # if it's a meta-type that refers to a generic float/int, just make that
         if dtype in (dt.Float, dt.Number):
@@ -66,7 +66,10 @@ def _lol_dtype(
             array_type = core_schema.union_schema(
                 [_lol_dtype(t, _handler) for t in types_]
             )
-
+    elif is_union(dtype):
+        array_type = core_schema.union_schema(
+            [_lol_dtype(t, _handler) for t in get_args(dtype)]
+        )
     else:
         try:
             python_type = np_to_python[dtype]
@@ -110,7 +113,7 @@ def list_of_lists_schema(shape: "Shape", array_type: CoreSchema) -> ListSchema:
         array_type ( :class:`pydantic_core.CoreSchema` ): The pre-rendered pydantic
             core schema to use in the innermost list entry
     """
-    from numpydantic.shape import _is_range
+    from numpydantic.validation.shape import _is_range
 
     shape_parts = [part.strip() for part in shape.__args__[0].split(",")]
     # labels, if present
diff --git a/src/numpydantic/serialization.py b/src/numpydantic/serialization.py
index 1f1edd0..07924eb 100644
--- a/src/numpydantic/serialization.py
+++ b/src/numpydantic/serialization.py
@@ -4,7 +4,7 @@ and :func:`pydantic.BaseModel.model_dump_json` .
 """
 
 from pathlib import Path
-from typing import Any, Callable, TypeVar, Union
+from typing import Any, Callable, Iterable, TypeVar, Union
 
 from pydantic_core.core_schema import SerializationInfo
 
@@ -16,6 +16,9 @@ U = TypeVar("U")
 
 def jsonize_array(value: Any, info: SerializationInfo) -> Union[list, dict]:
     """Use an interface class to render an array as JSON"""
+    # perf: keys to skip in generation - anything named "value" is array data.
+    skip = ["value"]
+
     interface_cls = Interface.match_output(value)
     array = interface_cls.to_json(value, info)
     if isinstance(array, JsonDict):
@@ -25,19 +28,37 @@ def jsonize_array(value: Any, info: SerializationInfo) -> Union[list, dict]:
         if info.context.get("mark_interface", False):
             array = interface_cls.mark_json(array)
 
+        if isinstance(array, list):
+            return array
+
+        # ---- Perf Barrier ------------------------------------------------------
+        # put context args intended to **wrap** the array above
+        # put context args intended to **modify** the array below
+        #
+        # above, we assume that a list is **data** not to be modified.
+        # below, we must mark whenever the data is in the line of fire
+        # to avoid an expensive iteration.
+
         if info.context.get("absolute_paths", False):
-            array = _absolutize_paths(array)
+            array = _absolutize_paths(array, skip)
         else:
             relative_to = info.context.get("relative_to", ".")
-            array = _relativize_paths(array, relative_to)
+            array = _relativize_paths(array, relative_to, skip)
     else:
-        # relativize paths by default
-        array = _relativize_paths(array, ".")
+        if isinstance(array, list):
+            return array
+
+        # ---- Perf Barrier ------------------------------------------------------
+        # same as above, ensure any keys that contain array values are skipped right now
+
+        array = _relativize_paths(array, ".", skip)
 
     return array
 
 
-def _relativize_paths(value: dict, relative_to: str = ".") -> dict:
+def _relativize_paths(
+    value: dict, relative_to: str = ".", skip: Iterable = tuple()
+) -> dict:
     """
     Make paths relative to either the current directory or the provided
     ``relative_to`` directory, if provided in the context
@@ -46,6 +67,8 @@ def _relativize_paths(value: dict, relative_to: str = ".") -> dict:
     # pdb.set_trace()
 
     def _r_path(v: Any) -> Any:
+        if not isinstance(v, (str, Path)):
+            return v
         try:
             path = Path(v)
             if not path.exists():
@@ -54,10 +77,10 @@ def _relativize_paths(value: dict, relative_to: str = ".") -> dict:
         except (TypeError, ValueError):
             return v
 
-    return _walk_and_apply(value, _r_path)
+    return _walk_and_apply(value, _r_path, skip)
 
 
-def _absolutize_paths(value: dict) -> dict:
+def _absolutize_paths(value: dict, skip: Iterable = tuple()) -> dict:
     def _a_path(v: Any) -> Any:
         try:
             path = Path(v)
@@ -67,23 +90,25 @@ def _absolutize_paths(value: dict) -> dict:
         except (TypeError, ValueError):
             return v
 
-    return _walk_and_apply(value, _a_path)
+    return _walk_and_apply(value, _a_path, skip)
 
 
-def _walk_and_apply(value: T, f: Callable[[U], U]) -> T:
+def _walk_and_apply(value: T, f: Callable[[U], U], skip: Iterable = tuple()) -> T:
     """
     Walk an object, applying a function
     """
     if isinstance(value, dict):
         for k, v in value.items():
+            if k in skip:
+                continue
             if isinstance(v, dict):
-                _walk_and_apply(v, f)
+                _walk_and_apply(v, f, skip)
             elif isinstance(v, list):
-                value[k] = [_walk_and_apply(sub_v, f) for sub_v in v]
+                value[k] = [_walk_and_apply(sub_v, f, skip) for sub_v in v]
             else:
                 value[k] = f(v)
     elif isinstance(value, list):
-        value = [_walk_and_apply(v, f) for v in value]
+        value = [_walk_and_apply(v, f, skip) for v in value]
     else:
         value = f(value)
     return value
diff --git a/src/numpydantic/validation/__init__.py b/src/numpydantic/validation/__init__.py
new file mode 100644
index 0000000..73d7374
--- /dev/null
+++ b/src/numpydantic/validation/__init__.py
@@ -0,0 +1,11 @@
+"""
+Helper functions for validation
+"""
+
+from numpydantic.validation.dtype import validate_dtype
+from numpydantic.validation.shape import validate_shape
+
+__all__ = [
+    "validate_dtype",
+    "validate_shape",
+]
diff --git a/src/numpydantic/validation/dtype.py b/src/numpydantic/validation/dtype.py
new file mode 100644
index 0000000..bc7723c
--- /dev/null
+++ b/src/numpydantic/validation/dtype.py
@@ -0,0 +1,55 @@
+"""
+Helper functions for validation of dtype.
+
+For literal dtypes intended for use by end-users, see :mod:`numpydantic.dtype`
+"""
+
+from types import UnionType
+from typing import Any, Union, get_args, get_origin
+
+import numpy as np
+
+from numpydantic.types import DtypeType
+
+
+def validate_dtype(dtype: Any, target: DtypeType) -> bool:
+    """
+    Validate a dtype against the target dtype
+
+    Args:
+        dtype: The dtype to validate
+        target (:class:`.DtypeType`): The target dtype
+
+    Returns:
+        bool: ``True`` if valid, ``False`` otherwise
+    """
+    if target is Any:
+        return True
+
+    if isinstance(target, tuple):
+        valid = dtype in target
+    elif is_union(target):
+        valid = any(
+            [validate_dtype(dtype, target_dt) for target_dt in get_args(target)]
+        )
+    elif target is np.str_:
+        valid = getattr(dtype, "type", None) in (np.str_, str) or dtype in (
+            np.str_,
+            str,
+        )
+    else:
+        # try to match as any subclass, if target is a class
+        try:
+            valid = issubclass(dtype, target)
+        except TypeError:
+            # expected, if dtype or target is not a class
+            valid = dtype == target
+
+    return valid
+
+
+def is_union(dtype: DtypeType) -> bool:
+    """
+    Check if a dtype is a union
+    """
+    return get_origin(dtype) in (Union, UnionType)
diff --git a/src/numpydantic/shape.py b/src/numpydantic/validation/shape.py
similarity index 98%
rename from src/numpydantic/shape.py
rename to src/numpydantic/validation/shape.py
index 62a567f..e899ecd 100644
--- a/src/numpydantic/shape.py
+++ b/src/numpydantic/validation/shape.py
@@ -2,7 +2,7 @@
 Declaration and validation functions for array shapes.
 
 Mostly a mildly modified version of nptyping's
-:func:`npytping.shape_expression.check_shape`
+:func:`npytping.shape_expression.validate_shape`
 and its internals to allow for extended syntax, including ranges of shapes.
 
 Modifications from nptyping:
@@ -105,7 +105,7 @@ def validate_shape_expression(shape_expression: Union[ShapeExpression, Any]) ->
 
 
 @lru_cache
-def check_shape(shape: ShapeTuple, target: "Shape") -> bool:
+def validate_shape(shape: ShapeTuple, target: "Shape") -> bool:
     """
     Check whether the given shape corresponds to the given shape_expression.
     :param shape: the shape in question.
diff --git a/tests/conftest.py b/tests/conftest.py
index c9035f4..076e95d 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -80,6 +80,8 @@ INTEGER: TypeAlias = NDArray[Shape["*, *, *"], Integer]
 FLOAT: TypeAlias = NDArray[Shape["*, *, *"], Float]
 STRING: TypeAlias = NDArray[Shape["*, *, *"], str]
 MODEL: TypeAlias = NDArray[Shape["*, *, *"], BasicModel]
+UNION_PIPE: TypeAlias = NDArray[Shape["*, *, *"], np.uint32 | np.float32]
+UNION_TYPE: TypeAlias = NDArray[Shape["*, *, *"], Union[np.uint32, np.float32]]
 
 
 @pytest.fixture(
@@ -147,6 +149,16 @@ def shape_cases(request) -> ValidationCase:
         ValidationCase(annotation=MODEL, dtype=BadModel, passes=False),
         ValidationCase(annotation=MODEL, dtype=int, passes=False),
         ValidationCase(annotation=MODEL, dtype=SubClass, passes=True),
+        ValidationCase(annotation=UNION_PIPE, dtype=np.uint32, passes=True),
+        ValidationCase(annotation=UNION_PIPE, dtype=np.float32, passes=True),
+        ValidationCase(annotation=UNION_PIPE, dtype=np.uint64, passes=False),
+        ValidationCase(annotation=UNION_PIPE, dtype=np.float64, passes=False),
+        ValidationCase(annotation=UNION_PIPE, dtype=str, passes=False),
+        ValidationCase(annotation=UNION_TYPE, dtype=np.uint32, passes=True),
+        ValidationCase(annotation=UNION_TYPE, dtype=np.float32, passes=True),
+        ValidationCase(annotation=UNION_TYPE, dtype=np.uint64, passes=False),
+        ValidationCase(annotation=UNION_TYPE, dtype=np.float64, passes=False),
+        ValidationCase(annotation=UNION_TYPE, dtype=str, passes=False),
     ],
     ids=[
         "float",
@@ -174,6 +186,16 @@ def shape_cases(request) -> ValidationCase:
         "model-badmodel",
         "model-int",
         "model-subclass",
+        "union-pipe-uint32",
+        "union-pipe-float32",
+        "union-pipe-uint64",
+        "union-pipe-float64",
+        "union-pipe-str",
+        "union-type-uint32",
+        "union-type-float32",
+        "union-type-uint64",
+        "union-type-float64",
+        "union-type-str",
     ],
 )
 def dtype_cases(request) -> ValidationCase:
diff --git a/tests/test_interface/test_zarr.py b/tests/test_interface/test_zarr.py
index ed5c252..6b21b20 100644
--- a/tests/test_interface/test_zarr.py
+++ b/tests/test_interface/test_zarr.py
@@ -151,7 +151,7 @@ def test_zarr_to_json(store, model_blank, roundtrip, dump_array):
 
     if roundtrip:
         if dump_array:
-            assert as_json["array"] == lol_array
+            assert as_json["value"] == lol_array
         else:
             if as_json.get("file", False):
                 assert "array" not in as_json