diff --git a/docs/docs/api-reference/index.md b/docs/docs/api-reference/index.md
index 4bd6f561..1a035c29 100644
--- a/docs/docs/api-reference/index.md
+++ b/docs/docs/api-reference/index.md
@@ -8,8 +8,8 @@ This section contains the reference detailing the functions and modules
 available in EasyScience.
 
 - [base_classes](base_classes.md) – Core abstract and helper base
-  classes used to build EasyScience objects (e.g. `ObjBase`,
-  `ModelBase`).
+  classes used to build EasyScience objects (e.g. `NewBase`,
+  `ModelBase`, `EasyList`).
 - [fitting](fitting.md) – Fitting utilities and interfaces, including
   `Fitter` and available minimizers.
 - [global_object](global_object.md) – Global singleton providing shared
@@ -23,4 +23,5 @@ available in EasyScience.
 - [utils](utils.md) – Miscellaneous utility functions and helpers (class
   tools, decorators, type helpers).
 - [variable](variable.md) – Descriptor types and variable abstractions
-  (e.g. `DescriptorNumber`, `Parameter`, `DescriptorArray`).
+  (e.g. `DescriptorNumber`, `Parameter`, `DescriptorArray`). All of them
+  are `NewBase` objects, serialized with `to_dict`/`from_dict`.
diff --git a/src/easyscience/base_classes/based_base.py b/src/easyscience/base_classes/based_base.py
index 4044fb7b..7070f93a 100644
--- a/src/easyscience/base_classes/based_base.py
+++ b/src/easyscience/base_classes/based_base.py
@@ -239,11 +239,11 @@ def __dir__(self) -> Iterable[str]:
 
     def __copy__(self) -> BasedBase:
         """Return a copy of the object."""
-        temp = self.as_dict(skip=['unique_name'])
+        temp = self.to_dict(skip=['unique_name'])
         new_obj = self.__class__.from_dict(temp)
         return new_obj
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
         """
         Convert an object into a full dictionary using
         ``SerializerDict``. This is a shortcut for
@@ -266,4 +266,4 @@ def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
             skip = []
         if 'unique_name' not in skip:
             skip.append('unique_name')
-        return super().as_dict(skip=skip)
+        return super().to_dict(skip=skip)
diff --git a/src/easyscience/base_classes/easy_list.py b/src/easyscience/base_classes/easy_list.py
index 23ac673d..f1f60acd 100644
--- a/src/easyscience/base_classes/easy_list.py
+++ b/src/easyscience/base_classes/easy_list.py
@@ -45,7 +45,10 @@ def __init__(
             Initial items to add to the list.
         protected_types : list[Type[NewBase]] | Type[NewBase] | None, default=None
             Types that are allowed in the list. Can be a single NewBase
-            subclass or a list of them. If None,. By default, None.
+            subclass or a list of them. If None, any ``NewBase`` object
+            is accepted, including descriptors and parameters. Note that
+            only ``ModelBase`` items contribute to ``get_all_variables``
+            and hence to fitting. By default, None.
         unique_name : Optional[str], default=None
             Optional unique name for the list. By default, None.
         display_name : Optional[str], default=None
diff --git a/src/easyscience/base_classes/new_base.py b/src/easyscience/base_classes/new_base.py
index 115677f1..106e6f3c 100644
--- a/src/easyscience/base_classes/new_base.py
+++ b/src/easyscience/base_classes/new_base.py
@@ -137,6 +137,14 @@ def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
         Dict[str, Any]
             Encoded object containing all information to reform an
             EasyScience object.
+
+        Notes
+        -----
+        A ``unique_name`` that was generated automatically is not
+        written; only an explicitly supplied one is, so that a
+        deserialized object gets a fresh name instead of clashing with
+        the original. Likewise ``display_name`` is omitted when it is
+        ``None``. Pass ``skip`` to drop further fields.
         """
         serializer = SerializerBase()
         if skip is None:
diff --git a/src/easyscience/fitting/multi_fitter.py b/src/easyscience/fitting/multi_fitter.py
index dbafa3b6..55933d4e 100644
--- a/src/easyscience/fitting/multi_fitter.py
+++ b/src/easyscience/fitting/multi_fitter.py
@@ -6,6 +6,7 @@
 import numpy as np
 
 from ..base_classes import EasyList
+from ..base_classes import ModelBase
 from .fitter import Fitter
 from .minimizers import FitResults
 
@@ -38,7 +39,7 @@ def __init__(
         # Aggregate the fit objects so a single object can be sent to Fitter.
         # *-unpacking keeps any sequence (list, tuple, etc) working, as the
         # old CollectionBase container did.
-        self._fit_objects = EasyList(*fit_objects)
+        self._fit_objects = EasyList(*fit_objects, protected_types=ModelBase)
         self._fit_functions = list(fit_functions)
         # Initialize with the first of the fit_functions, without this it is
         # not possible to change the fitting engine. With no functions given
diff --git a/src/easyscience/io/serializer_base.py b/src/easyscience/io/serializer_base.py
index 5d9b0e51..26b1ad72 100644
--- a/src/easyscience/io/serializer_base.py
+++ b/src/easyscience/io/serializer_base.py
@@ -215,13 +215,13 @@ def runner(o):
                                     err = False
                             if err:
                                 raise NotImplementedError(
-                                    'Unable to automatically determine as_dict '
+                                    'Unable to automatically determine to_dict '
                                     'format from class. MSONAble requires all '
                                     'args to be present as either self.argname or '
                                     'self._argname, and kwargs to be present under'
                                     'a self.kwargs variable to automatically '
                                     'determine the dict format. Alternatively, '
-                                    'you can implement both as_dict and from_dict.'
+                                    'you can implement both to_dict and from_dict.'
                                 )
                 d[c] = self._recursive_encoder(
                     a, skip=skip, encoder=self, full_encode=full_encode, **kwargs
diff --git a/src/easyscience/io/serializer_component.py b/src/easyscience/io/serializer_component.py
index 10c5f7aa..9ef079ab 100644
--- a/src/easyscience/io/serializer_component.py
+++ b/src/easyscience/io/serializer_component.py
@@ -26,7 +26,7 @@ class SerializerComponent:
     """
 
     def __deepcopy__(self, memo):
-        return self.from_dict(self.as_dict())
+        return self.from_dict(self.to_dict())
 
     def encode(
         self, skip: Optional[List[str]] = None, encoder: Optional[SerializerBase] = None, **kwargs
@@ -82,7 +82,7 @@ def decode(cls, obj: Any, decoder: Optional[SerializerBase] = None) -> Any:
             decoder = SerializerDict
         return decoder.decode(obj)
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
         """
         Convert an EasyScience object into a full dictionary using
         ``SerializerDict``. This is a shortcut for
diff --git a/src/easyscience/job/theoreticalmodel.py b/src/easyscience/job/theoreticalmodel.py
index 3fa87e50..3cddec7e 100644
--- a/src/easyscience/job/theoreticalmodel.py
+++ b/src/easyscience/job/theoreticalmodel.py
@@ -18,6 +18,6 @@ def __init__(self, name: str, *args, **kwargs):
     def __str__(self):
         raise NotImplementedError('Copy not implemented')
 
-    def as_dict(self, skip: list = []) -> dict:
-        this_dict = super().as_dict(skip=skip)
+    def to_dict(self, skip: list = []) -> dict:
+        this_dict = super().to_dict(skip=skip)
         return this_dict
diff --git a/src/easyscience/variable/descriptor_any_type.py b/src/easyscience/variable/descriptor_any_type.py
index 157117d8..06f52dbf 100644
--- a/src/easyscience/variable/descriptor_any_type.py
+++ b/src/easyscience/variable/descriptor_any_type.py
@@ -34,7 +34,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
     ):
         """
         Constructor for the DescriptorAnyType class.
@@ -42,9 +41,9 @@ def __init__(
         param name: Name of the descriptor param value: Value of the
         descriptor param description: Description of the descriptor
         param url: URL of the descriptor param display_name: Display
-        name of the descriptor param parent: Parent of the descriptor ..
-        note:: Undo/Redo functionality is implemented for the attributes
-        ``variance``, ``error``, ``unit`` and ``value``.
+        name of the descriptor .. note:: Undo/Redo functionality is
+        implemented for the attributes ``variance``, ``error``,
+        ``unit`` and ``value``.
         """
 
         self._value = value
@@ -55,7 +54,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
         )
 
     @property
@@ -99,7 +97,7 @@ def __repr__(self) -> str:
 
         return f"<{self.__class__.__name__} '{self._name}': {value_repr}>"
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
-        raw_dict = super().as_dict(skip=skip)
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+        raw_dict = super().to_dict(skip=skip)
         raw_dict['value'] = self._value
         return raw_dict
diff --git a/src/easyscience/variable/descriptor_array.py b/src/easyscience/variable/descriptor_array.py
index 35f1c022..de6c0dac 100644
--- a/src/easyscience/variable/descriptor_array.py
+++ b/src/easyscience/variable/descriptor_array.py
@@ -42,7 +42,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
         dimensions: Optional[list] = None,
     ):
         """
@@ -52,11 +51,11 @@ def __init__(
         the values of the descriptor param unit: Unit of the descriptor
         param variance: Variances of the descriptor param description:
         Description of the descriptor param url: URL of the descriptor
-        param display_name: Display name of the descriptor param parent:
-        Parent of the descriptor param dimensions: List of dimensions to
-        pass to scipp. Will be autogenerated if not supplied. .. note::
-        Undo/Redo functionality is implemented for the attributes
-        ``variance``, ``error``, ``unit`` and ``value``.
+        param display_name: Display name of the descriptor param
+        dimensions: List of dimensions to pass to scipp. Will be
+        autogenerated if not supplied. .. note:: Undo/Redo functionality
+        is implemented for the attributes ``variance``, ``error``,
+        ``unit`` and ``value``.
         """
 
         if not isinstance(value, (list, np.ndarray)):
@@ -104,7 +103,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
         )
 
         # Call convert_unit during initialization to ensure that the unit has no numbers in it, and to ensure unit consistency.
@@ -472,14 +470,14 @@ def __repr__(self) -> str:
         string = string.replace('\n', ',')
         return string
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
         """
         Dict representation of the current DescriptorArray.
 
         The dict contains the value, unit and variances, in addition to
         the properties of DescriptorBase.
         """
-        raw_dict = super().as_dict(skip=skip)
+        raw_dict = super().to_dict(skip=skip)
         raw_dict['value'] = self._array.values
         raw_dict['unit'] = str(self._array.unit)
         raw_dict['variance'] = self._array.variances
diff --git a/src/easyscience/variable/descriptor_base.py b/src/easyscience/variable/descriptor_base.py
index ba7198bc..e2214d3a 100644
--- a/src/easyscience/variable/descriptor_base.py
+++ b/src/easyscience/variable/descriptor_base.py
@@ -5,14 +5,16 @@
 
 import abc
 from typing import Any
+from typing import Dict
+from typing import List
 from typing import Optional
 
 from easyscience import global_object
+from easyscience.base_classes.new_base import NewBase
 from easyscience.global_object.undo_redo import property_stack
-from easyscience.io import SerializerComponent
 
 
-class DescriptorBase(SerializerComponent, metaclass=abc.ABCMeta):
+class DescriptorBase(NewBase, metaclass=abc.ABCMeta):
     """
     This is the base of all variable descriptions for models.
 
@@ -29,7 +31,7 @@ class DescriptorBase(SerializerComponent, metaclass=abc.ABCMeta):
 
     _global_object = global_object
     # Used by serializer
-    _REDIRECT = {'parent': None}
+    _REDIRECT = {}
 
     def __init__(
         self,
@@ -38,7 +40,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
     ):
         """
         This is the base of variables for models.
@@ -63,9 +64,6 @@ def __init__(
             Lookup url for documentation/information. By default, None.
         display_name : Optional[str], default=None
             A pretty name for the object. By default, None.
-        parent : Optional[Any], default=None
-            The object which this descriptor is attached to. By default,
-            None.
 
         Raises
         ------
@@ -74,17 +72,12 @@ def __init__(
             has an invalid type.
         """
 
-        if unique_name is None:
-            unique_name = global_object.generate_unique_name(self.__class__.__name__)
-        self._unique_name = unique_name
-
         if not isinstance(name, str):
             raise TypeError('Name must be a string')
-        self._name: str = name
 
-        if display_name is not None and not isinstance(display_name, str):
-            raise TypeError('Display name must be a string or None')
-        self._display_name: str = display_name
+        super().__init__(unique_name=unique_name, display_name=display_name)
+
+        self._name: str = name
 
         if description is not None and not isinstance(description, str):
             raise TypeError('Description must be a string or None')
@@ -98,13 +91,6 @@ def __init__(
             url = ''
         self._url: str = url
 
-        # Let the collective know we've been assimilated
-        self._parent = parent
-        global_object.map.add_vertex(self, obj_type='created')
-        # Make the connection between self and parent
-        if parent is not None:
-            global_object.map.add_edge(parent, self)
-
     @property
     def name(self) -> str:
         """
@@ -142,6 +128,9 @@ def display_name(self) -> str:
         """
         Get a pretty display name.
 
+        Unlike ``NewBase`` the fallback is the ``name`` of the
+        descriptor rather than its ``unique_name``.
+
         Returns
         -------
         str
@@ -234,40 +223,6 @@ def url(self, url: Optional[str]) -> None:
             raise TypeError('url must be a string')
         self._url = url
 
-    @property
-    def unique_name(self) -> str:
-        """
-        Get the unique name of this object.
-
-        Returns
-        -------
-        str
-            Unique name of this object.
-        """
-        return self._unique_name
-
-    @unique_name.setter
-    def unique_name(self, new_unique_name: str):
-        """
-        Set a new unique name for the object.
-
-        The old name is still kept in the map.
-
-        Parameters
-        ----------
-        new_unique_name : str
-            New unique name for the object.
-
-        Raises
-        ------
-        TypeError
-            If ``new_unique_name`` is not a string.
-        """
-        if not isinstance(new_unique_name, str):
-            raise TypeError('Unique name has to be a string.')
-        self._unique_name = new_unique_name
-        global_object.map.add_vertex(self)
-
     @property
     @abc.abstractmethod
     def value(self) -> Any:
@@ -281,9 +236,3 @@ def value(self, value: Any) -> None:
     @abc.abstractmethod
     def __repr__(self) -> str:
         """Return printable representation of the object."""
-
-    def __copy__(self) -> DescriptorBase:
-        """Return a copy of the object."""
-        temp = self.as_dict(skip=['unique_name'])
-        new_obj = self.__class__.from_dict(temp)
-        return new_obj
diff --git a/src/easyscience/variable/descriptor_bool.py b/src/easyscience/variable/descriptor_bool.py
index 05a09d9d..874509fc 100644
--- a/src/easyscience/variable/descriptor_bool.py
+++ b/src/easyscience/variable/descriptor_bool.py
@@ -3,7 +3,6 @@
 
 from __future__ import annotations
 
-from typing import Any
 from typing import Optional
 
 from easyscience.global_object.undo_redo import property_stack
@@ -22,7 +21,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
     ):
         if not isinstance(value, bool):
             raise ValueError(f'{value=} must be type bool')
@@ -32,7 +30,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
         )
         if not isinstance(value, bool):
             raise TypeError(f'{value=} must be type bool')
diff --git a/src/easyscience/variable/descriptor_number.py b/src/easyscience/variable/descriptor_number.py
index 5bcbcb0d..c2a97262 100644
--- a/src/easyscience/variable/descriptor_number.py
+++ b/src/easyscience/variable/descriptor_number.py
@@ -65,7 +65,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
         **kwargs: Any,  # Additional keyword arguments (used for (de)serialization)
     ):
         """
@@ -75,9 +74,9 @@ def __init__(
         descriptor param unit: Unit of the descriptor param variance:
         Variance of the descriptor param description: Description of the
         descriptor param url: URL of the descriptor param display_name:
-        Display name of the descriptor param parent: Parent of the
-        descriptor .. note:: Undo/Redo functionality is implemented for
-        the attributes ``variance``, ``error``, ``unit`` and ``value``.
+        Display name of the descriptor .. note:: Undo/Redo functionality
+        is implemented for the attributes ``variance``, ``error``,
+        ``unit`` and ``value``.
         """
         self._observers: List[DescriptorNumber] = []
 
@@ -107,7 +106,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
         )
 
         # Call convert_unit during initialization to ensure that the unit has no numbers in it, and to ensure unit consistency.
@@ -444,8 +442,8 @@ def __repr__(self) -> str:
         return string
         # return f"<{class_name} '{obj_name}': {obj_value:0.04f}{obj_unit}>"
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
-        raw_dict = super().as_dict(skip=skip)
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+        raw_dict = super().to_dict(skip=skip)
         raw_dict['value'] = self._scalar.value
         raw_dict['unit'] = str(self._scalar.unit)
         raw_dict['variance'] = self._scalar.variance
diff --git a/src/easyscience/variable/descriptor_str.py b/src/easyscience/variable/descriptor_str.py
index 5e74e786..e4b28823 100644
--- a/src/easyscience/variable/descriptor_str.py
+++ b/src/easyscience/variable/descriptor_str.py
@@ -3,7 +3,6 @@
 
 from __future__ import annotations
 
-from typing import Any
 from typing import Optional
 
 from easyscience.global_object.undo_redo import property_stack
@@ -22,7 +21,6 @@ def __init__(
         description: Optional[str] = None,
         url: Optional[str] = None,
         display_name: Optional[str] = None,
-        parent: Optional[Any] = None,
     ):
         super().__init__(
             name=name,
@@ -30,7 +28,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
         )
         if not isinstance(value, str):
             raise ValueError(f'{value=} must be type str')
diff --git a/src/easyscience/variable/parameter.py b/src/easyscience/variable/parameter.py
index 3ec654f7..35654ed5 100644
--- a/src/easyscience/variable/parameter.py
+++ b/src/easyscience/variable/parameter.py
@@ -52,7 +52,6 @@ def __init__(
         url: Optional[str] = None,
         display_name: Optional[str] = None,
         callback: property = property(),
-        parent: Optional[Any] = None,
         **kwargs: Any,  # Additional keyword arguments (used for (de)serialization)
     ):
         """
@@ -92,9 +91,6 @@ def __init__(
         callback : property, default=property()
             Callback used to synchronize the parameter with an external
             model.
-        parent : Optional[Any], default=None
-            The object which is the parent to this one. By default,
-            None.
         **kwargs : Any
             Additional keyword arguments used during serialization.
 
@@ -147,7 +143,6 @@ def __init__(
             description=description,
             url=url,
             display_name=display_name,
-            parent=parent,
             **kwargs,  # Additional keyword arguments (used for (de)serialization)
         )
 
@@ -903,11 +898,11 @@ def free(self) -> bool:
     def free(self, value: bool) -> None:
         self.fixed = not value
 
-    def as_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
+    def to_dict(self, skip: Optional[List[str]] = None) -> Dict[str, Any]:
         """
-        Overwrite the as_dict method to handle dependency information.
+        Overwrite the to_dict method to handle dependency information.
         """
-        raw_dict = super().as_dict(skip=skip)
+        raw_dict = super().to_dict(skip=skip)
 
         # Add dependency information for dependent parameters
         if not self._independent:
diff --git a/tests/unit/base_classes/test_collection_base.py b/tests/unit/base_classes/test_collection_base.py
index 732c3acf..8886a474 100644
--- a/tests/unit/base_classes/test_collection_base.py
+++ b/tests/unit/base_classes/test_collection_base.py
@@ -305,7 +305,7 @@ def test_CollectionBase_dir(cls):
         'append',
         'unique_name',
         'index',
-        'as_dict',
+        'to_dict',
         'clear',
         'extend',
         'encode',
@@ -327,11 +327,11 @@ def test_CollectionBase_dir(cls):
 
 
 @pytest.mark.parametrize('cls', class_constructors)
-def test_CollectionBase_as_dict(cls):
+def test_CollectionBase_to_dict(cls):
     name = 'testing'
     kwargs = {'p1': DescriptorNumber('par1', 1)}
     obj = cls(name, **kwargs)
-    d = obj.as_dict()
+    d = obj.to_dict()
 
     def check_dict(dict_1: dict, dict_2: dict):
         keys_1 = list(dict_1.keys())
@@ -423,7 +423,7 @@ def test_CollectionBase_iterator_dict(cls):
     l_object = [p1, p2, p3, p4]
 
     obj = cls(name, *l_object)
-    d = obj.as_dict()
+    d = obj.to_dict()
     global_object.map._clear()
     obj2 = cls.from_dict(d)
 
diff --git a/tests/unit/base_classes/test_obj_base.py b/tests/unit/base_classes/test_obj_base.py
index 5eb1b2ea..723d617f 100644
--- a/tests/unit/base_classes/test_obj_base.py
+++ b/tests/unit/base_classes/test_obj_base.py
@@ -141,11 +141,11 @@ def test_ObjBase_fit_objects(setup_pars: dict):
     pass
 
 
-def test_ObjBase_as_dict(clear, setup_pars: dict):
+def test_ObjBase_to_dict(clear, setup_pars: dict):
     name = setup_pars['name']
     del setup_pars['name']
     obj = ObjBase(name, **setup_pars)
-    obtained = obj.as_dict()
+    obtained = obj.to_dict()
     assert isinstance(obtained, dict)
     expected = {
         '@module': 'easyscience.legacy.obj_base',
@@ -238,7 +238,7 @@ def test_ObjBase_dict_roundtrip(clear, setup_pars: dict):
     name = setup_pars['name']
     del setup_pars['name']
     obj = ObjBase(name, **setup_pars, unique_name='special_name')
-    obj_dict = obj.as_dict()
+    obj_dict = obj.to_dict()
 
     global_object.map._clear()
 
@@ -246,7 +246,7 @@ def test_ObjBase_dict_roundtrip(clear, setup_pars: dict):
     new_obj = ObjBase.from_dict(obj_dict)
 
     # Expect
-    new_obj_dict = new_obj.as_dict()
+    new_obj_dict = new_obj.to_dict()
     assert obj_dict == new_obj_dict
 
 
@@ -257,7 +257,7 @@ def test_ObjBase_dir(setup_pars):
     expected = [
         'encode',
         'decode',
-        'as_dict',
+        'to_dict',
         'des1',
         'des2',
         'from_dict',
diff --git a/tests/unit/fitting/test_multi_fitter.py b/tests/unit/fitting/test_multi_fitter.py
index 1960affe..3af44358 100644
--- a/tests/unit/fitting/test_multi_fitter.py
+++ b/tests/unit/fitting/test_multi_fitter.py
@@ -259,7 +259,9 @@ def test_rejects_foreign_object(self):
             MultiFitter([Line(1.0, 0.5), 'not a model'], [None, None])
 
     def test_rejects_bare_parameter(self):
-        """CollectionBase accepted bare parameters; EasyList does not."""
+        """CollectionBase accepted bare parameters; the ModelBase-gated
+        EasyList does not (a Parameter is a NewBase, but EasyList only
+        harvests parameters from ModelBase members)."""
         model = Line(1.0, 0.5)
         with pytest.raises(TypeError, match='Items must be one of'):
             MultiFitter([model, Parameter('p', 1.0)], [model, None])
diff --git a/tests/unit/global_object/test_integration_comprehensive.py b/tests/unit/global_object/test_integration_comprehensive.py
index 61268954..541c9e46 100644
--- a/tests/unit/global_object/test_integration_comprehensive.py
+++ b/tests/unit/global_object/test_integration_comprehensive.py
@@ -361,8 +361,8 @@ def test_serialization_integration_with_global_state(self, clear_all):
         original_vertex_count = len(global_obj.map.vertices())
 
         # When - Serialize objects
-        param_dict = param.as_dict()
-        obj_dict = obj.as_dict()
+        param_dict = param.to_dict()
+        obj_dict = obj.to_dict()
 
         # Clear global state
         global_obj.map._clear()
diff --git a/tests/unit/io/test_serializer_base.py b/tests/unit/io/test_serializer_base.py
index c3c8dd21..550c4d75 100644
--- a/tests/unit/io/test_serializer_base.py
+++ b/tests/unit/io/test_serializer_base.py
@@ -471,7 +471,7 @@ def __init__(self, name: str, missing_param: str = 'default'):
 
         obj = MockObjMissingAttrs('test')
 
-        with pytest.raises(NotImplementedError, match='Unable to automatically determine as_dict'):
+        with pytest.raises(NotImplementedError, match='Unable to automatically determine to_dict'):
             serializer._convert_to_dict(obj)
 
     def test_convert_to_dict_with_kwargs_attribute(self, serializer, clear):
diff --git a/tests/unit/io/test_serializer_component.py b/tests/unit/io/test_serializer_component.py
index c4e21f49..a90e364c 100644
--- a/tests/unit/io/test_serializer_component.py
+++ b/tests/unit/io/test_serializer_component.py
@@ -71,7 +71,7 @@ def check_dict(check, item):
 
 @pytest.mark.parametrize(**skip_dict)
 @pytest.mark.parametrize(**dp_param_dict)
-def test_variable_as_dict_methods(dp_kwargs: dict, dp_cls: Type[DescriptorNumber], skip):
+def test_variable_to_dict_methods(dp_kwargs: dict, dp_cls: Type[DescriptorNumber], skip):
     data_dict = {k: v for k, v in dp_kwargs.items() if k[0] != '@'}
 
     obj = dp_cls(**data_dict)
@@ -84,7 +84,7 @@ def test_variable_as_dict_methods(dp_kwargs: dict, dp_cls: Type[DescriptorNumber
     if not isinstance(skip, list):
         skip = [skip]
 
-    enc = obj.as_dict(skip=skip)
+    enc = obj.to_dict(skip=skip)
 
     expected_keys = set(dp_kwargs.keys())
     obtained_keys = set(enc.keys())
diff --git a/tests/unit/io/test_serializer_dict.py b/tests/unit/io/test_serializer_dict.py
index 1ddf21ef..1b37fae9 100644
--- a/tests/unit/io/test_serializer_dict.py
+++ b/tests/unit/io/test_serializer_dict.py
@@ -50,7 +50,7 @@ def test_variable_SerializerDict(dp_kwargs: dict, dp_cls: Type[DescriptorNumber]
     if not isinstance(skip, list):
         skip = [skip]
 
-    enc = obj.encode(skip=skip, encoder=SerializerDict)
+    enc = SerializerDict().encode(obj, skip=skip)
 
     expected_keys = set(dp_kwargs.keys())
     obtained_keys = set(enc.keys())
@@ -71,9 +71,9 @@ def test_variable_SerializerDict_decode(dp_kwargs: dict, dp_cls: Type[Descriptor
 
     obj = dp_cls(**data_dict)
 
-    enc = obj.encode(encoder=SerializerDict)
+    enc = SerializerDict().encode(obj)
     global_object.map._clear()
-    dec = dp_cls.decode(enc, decoder=SerializerDict)
+    dec = SerializerDict.decode(enc)
 
     for k in data_dict.keys():
         if hasattr(obj, k) and hasattr(dec, k):
@@ -88,7 +88,7 @@ def test_variable_SerializerDict_from_dict(dp_kwargs: dict, dp_cls: Type[Descrip
 
     obj = dp_cls(**data_dict)
 
-    enc = obj.encode(encoder=SerializerDict)
+    enc = SerializerDict().encode(obj)
     global_object.map._clear()
     dec = dp_cls.from_dict(enc)
 
@@ -106,7 +106,7 @@ def test_group_encode():
     from easyscience.base_classes import CollectionBase
 
     b = CollectionBase('test', d0, d1)
-    d = b.as_dict()
+    d = b.to_dict()
     assert isinstance(d['data'], list)
 
 
@@ -117,5 +117,5 @@ def test_group_encode2():
     from easyscience.base_classes import CollectionBase
 
     b = ObjBase('outer', b=CollectionBase('test', d0, d1))
-    d = b.as_dict()
+    d = b.to_dict()
     assert isinstance(d['b'], dict)
diff --git a/tests/unit/variable/test_descriptor_any_type.py b/tests/unit/variable/test_descriptor_any_type.py
index 5dc28b58..12db376a 100644
--- a/tests/unit/variable/test_descriptor_any_type.py
+++ b/tests/unit/variable/test_descriptor_any_type.py
@@ -17,7 +17,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
diff --git a/tests/unit/variable/test_descriptor_array.py b/tests/unit/variable/test_descriptor_array.py
index 73bb0857..36ede2e3 100644
--- a/tests/unit/variable/test_descriptor_array.py
+++ b/tests/unit/variable/test_descriptor_array.py
@@ -23,7 +23,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -37,7 +36,6 @@ def descriptor_dimensionless(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -67,7 +65,6 @@ def test_init_sc_unit(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
 
         # Expect
@@ -86,7 +83,6 @@ def test_init_sc_unit_unknown(self):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     @pytest.mark.parametrize('value', [True, 'string'])
@@ -103,7 +99,6 @@ def test_init_value_type_exception(self, value):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     def test_init_variance_exception(self):
@@ -119,7 +114,6 @@ def test_init_variance_exception(self):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     # test from_scipp
@@ -1481,7 +1475,6 @@ def test_negation(self, descriptor):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         assert type(result) == DescriptorArray
         assert result.name == result.unique_name
@@ -1500,7 +1493,6 @@ def test_abs(self, descriptor):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
 
         # Then
diff --git a/tests/unit/variable/test_descriptor_base.py b/tests/unit/variable/test_descriptor_base.py
index 24c342dc..9661afa3 100644
--- a/tests/unit/variable/test_descriptor_base.py
+++ b/tests/unit/variable/test_descriptor_base.py
@@ -4,6 +4,10 @@
 import pytest
 
 from easyscience import global_object
+from easyscience.base_classes import EasyList
+from easyscience.base_classes import NewBase
+from easyscience.io import SerializerComponent
+from easyscience.variable import DescriptorNumber
 from easyscience.variable.descriptor_base import DescriptorBase
 
 
@@ -19,7 +23,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -40,7 +43,6 @@ def test_init_name_type_error(self, name):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     @pytest.mark.parametrize(
@@ -56,7 +58,6 @@ def test_init_display_name_type_error(self, display_name):
                 description='description',
                 url='url',
                 display_name=display_name,
-                parent=None,
             )
 
     @pytest.mark.parametrize(
@@ -72,7 +73,6 @@ def test_init_description_type_error(self, description):
                 description=description,
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     @pytest.mark.parametrize(
@@ -88,7 +88,6 @@ def test_init_url_type_error(self, url):
                 description='description',
                 url=url,
                 display_name='display_name',
-                parent=None,
             )
 
     def test_init(self, descriptor: DescriptorBase):
diff --git a/tests/unit/variable/test_descriptor_bool.py b/tests/unit/variable/test_descriptor_bool.py
index 3c181f0e..48372485 100644
--- a/tests/unit/variable/test_descriptor_bool.py
+++ b/tests/unit/variable/test_descriptor_bool.py
@@ -16,7 +16,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -45,7 +44,6 @@ def test_init_bool_value_type_exception(self, bool_value):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     def test_value(self, descriptor: DescriptorBool):
diff --git a/tests/unit/variable/test_descriptor_number.py b/tests/unit/variable/test_descriptor_number.py
index 6abd3029..3d3f7331 100644
--- a/tests/unit/variable/test_descriptor_number.py
+++ b/tests/unit/variable/test_descriptor_number.py
@@ -20,7 +20,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -51,7 +50,6 @@ def test_init_sc_unit(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
 
         # Expect
@@ -70,7 +68,6 @@ def test_init_sc_unit_unknown(self):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     @pytest.mark.parametrize('value', [True, 'string'])
@@ -87,7 +84,6 @@ def test_init_value_type_exception(self, value):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     def test_init_variance_exception(self):
@@ -104,7 +100,6 @@ def test_init_variance_exception(self):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     # test from_scipp
diff --git a/tests/unit/variable/test_descriptor_str.py b/tests/unit/variable/test_descriptor_str.py
index 46acc847..36b721c1 100644
--- a/tests/unit/variable/test_descriptor_str.py
+++ b/tests/unit/variable/test_descriptor_str.py
@@ -16,7 +16,6 @@ def descriptor(self):
             description='description',
             url='url',
             display_name='display_name',
-            parent=None,
         )
         return descriptor
 
@@ -44,7 +43,6 @@ def test_init_string_type_exception(self, string):
                 description='description',
                 url='url',
                 display_name='display_name',
-                parent=None,
             )
 
     def test_value(self, descriptor: DescriptorStr):
diff --git a/tests/unit/variable/test_parameter.py b/tests/unit/variable/test_parameter.py
index 1ac05b45..5376edf3 100644
--- a/tests/unit/variable/test_parameter.py
+++ b/tests/unit/variable/test_parameter.py
@@ -29,7 +29,6 @@ def parameter(self) -> Parameter:
             url='url',
             display_name='display_name',
             callback=self.mock_callback,
-            parent=None,
         )
         return parameter
 
@@ -96,7 +95,6 @@ def test_init_value_min_exception(self):
                 url='url',
                 display_name='display_name',
                 callback=mock_callback,
-                parent=None,
             )
 
     def test_init_value_max_exception(self):
@@ -117,7 +115,6 @@ def test_init_value_max_exception(self):
                 url='url',
                 display_name='display_name',
                 callback=mock_callback,
-                parent=None,
             )
 
     def test_make_dependent_on(self, normal_parameter: Parameter):
diff --git a/tests/unit/variable/test_parameter_dependency_serialization.py b/tests/unit/variable/test_parameter_dependency_serialization.py
index 62feb5f3..98daed45 100644
--- a/tests/unit/variable/test_parameter_dependency_serialization.py
+++ b/tests/unit/variable/test_parameter_dependency_serialization.py
@@ -40,7 +40,7 @@ def test_independent_parameter_serialization(self, clear_global_map):
         param = Parameter(name='test', value=5.0, unit='m', min=0, max=10)
 
         # Serialize
-        serialized = param.as_dict()
+        serialized = param.to_dict()
 
         # Should not contain dependency fields
         assert '_dependency_string' not in serialized
@@ -68,7 +68,7 @@ def test_dependent_parameter_serialization(self, clear_global_map):
         )
 
         # Serialize dependent parameter
-        serialized = b.as_dict()
+        serialized = b.to_dict()
 
         # Should contain dependency information
         assert serialized['_dependency_string'] == '2 * a'
@@ -106,7 +106,7 @@ def test_dependency_resolution_after_deserialization(self, clear_global_map):
         assert c.value == 5.0  # 2 + 3
 
         # Serialize all parameters
-        params_data = {'a': a.as_dict(), 'b': b.as_dict(), 'c': c.as_dict()}
+        params_data = {'a': a.to_dict(), 'b': b.to_dict(), 'c': c.to_dict()}
 
         # Clear and deserialize (manual approach)
         global_object.map._clear()
@@ -151,7 +151,7 @@ def test_dependency_resolution_after_deserialization_desired_unit(self, clear_gl
         assert c.unit == 'cm'
 
         # Serialize all parameters
-        params_data = {'a': a.as_dict(), 'b': b.as_dict(), 'c': c.as_dict()}
+        params_data = {'a': a.to_dict(), 'b': b.to_dict(), 'c': c.to_dict()}
 
         # Clear and deserialize (manual approach)
         global_object.map._clear()
@@ -192,8 +192,8 @@ def test_unique_name_dependency_serialization(self, clear_global_map):
         )
 
         # Serialize both parameters
-        a_serialized = a.as_dict()
-        b_serialized = b.as_dict()
+        a_serialized = a.to_dict()
+        b_serialized = b.to_dict()
 
         # Should contain unique name mapping
         assert b_serialized['_dependency_string'] == '2 * __Parameter_0__'
@@ -237,9 +237,9 @@ def test_json_serialization_roundtrip(self, clear_global_map):
 
         # Serialize to JSON
         params_data = {
-            'length': length.as_dict(),
-            'width': width.as_dict(),
-            'area': area.as_dict(),
+            'length': length.to_dict(),
+            'width': width.to_dict(),
+            'area': area.to_dict(),
         }
         json_str = json.dumps(params_data, default=str)
 
@@ -281,7 +281,7 @@ def test_multiple_dependent_parameters(self, clear_global_map):
         assert z.value == 6.0  # 4 + 2
 
         # Serialize all
-        params_data = {'x': x.as_dict(), 'y': y.as_dict(), 'z': z.as_dict()}
+        params_data = {'x': x.to_dict(), 'y': y.to_dict(), 'z': z.to_dict()}
 
         # Deserialize and resolve
         global_object.map._clear()
@@ -319,7 +319,7 @@ def test_dependency_with_descriptor_number(self, clear_global_map):
 
         # Then
         # Serialize all
-        params_data = {'x': x.as_dict(), 'y': y.as_dict(), 'z': z.as_dict()}
+        params_data = {'x': x.to_dict(), 'y': y.to_dict(), 'z': z.to_dict()}
         # Deserialize and resolve
         global_object.map._clear()
         new_params = {}
@@ -350,7 +350,7 @@ def test_get_parameters_with_pending_dependencies(self, clear_global_map):
         )
 
         # Serialize and deserialize
-        params_data = {'a': a.as_dict(), 'b': b.as_dict()}
+        params_data = {'a': a.to_dict(), 'b': b.to_dict()}
         global_object.map._clear()
         new_params = {}
         for name, data in params_data.items():
@@ -376,7 +376,7 @@ def test_error_handling_missing_dependency(self, clear_global_map):
         )
 
         # Serialize b but not a
-        b_data = b.as_dict()
+        b_data = b.to_dict()
 
         # Deserialize without a in the global map
         global_object.map._clear()
@@ -397,7 +397,7 @@ def test_backward_compatibility_base_deserializer(self, clear_global_map):
         )
 
         # Use base serializer path (SerializerDict.decode)
-        serialized = b.encode(encoder=SerializerDict)
+        serialized = SerializerDict().encode(b)
         global_object.map._clear()
 
         # This should not raise the "_independent" error anymore
@@ -440,7 +440,7 @@ def test_serializer_id_system_order_independence(self, clear_global_map, order):
         y_dep_id = y._DescriptorNumber__serializer_id
 
         # Serialize all parameters
-        params_data = {'x': x.as_dict(), 'y': y.as_dict(), 'z': z.as_dict()}
+        params_data = {'x': x.to_dict(), 'y': y.to_dict(), 'z': z.to_dict()}
 
         # Verify dependency IDs are in serialized data
         assert params_data['x']['__serializer_id'] == x_dep_id
@@ -492,7 +492,7 @@ def test_deserialize_and_resolve_parameters_helper(self, clear_global_map):
         assert c.value == 5.0  # 2 + 3
 
         # Serialize all parameters
-        params_data = {'a': a.as_dict(), 'b': b.as_dict(), 'c': c.as_dict()}
+        params_data = {'a': a.to_dict(), 'b': b.to_dict(), 'c': c.to_dict()}
 
         # Clear global map
         global_object.map._clear()