remove assignment validation from docs

docs/roman_datamodels/datamodels/general_structure.rst

@@ -259,7 +259,8 @@ ref_optical_element-1.0.0::
   ...
 
 If one tries to modify the datamodel contents with a value inconsistent with
-what a schema requires, validation will raise an error.
+what a schema requires, validation will raise an error when the datamodel is
+validated.
 
 Level 1 Example
 ...............

docs/roman_datamodels/datamodels/stnode.rst

@@ -78,8 +78,8 @@ The specific stnode objects will be subclasses of the
 `~roman_datamodels.stnode.TaggedObjectNode` or
 `~roman_datamodels.stnode.TaggedListNode` classes. These classes are extensions
 of the `~roman_datamodels.stnode.DNode` and `~roman_datamodels.stnode.LNode`
-classes which have extensions to handle looking up the schema information for on
-the fly data validation. In particular, they will track the ``tag`` information
+classes which have extensions to handle looking up the schema information.
+In particular, they will track the ``tag`` information
 contained within the manifest from RAD.
 
 These "tagged-nodes" are then turned into specific stnode objects via the
@@ -126,46 +126,6 @@ is reorganized, then scalar node concept can be removed from the codebase.
     dictionary.
 
 
-Validation
-----------
-
-The stnode objects are designed to attempt to validate the data they contain or
-have set in them against the schema information in RAD. This is typically done
-on the fly when the data is set via the ``.`` interface; however, ASDF by
-default will validate the data stored in the node against its schema during both
-serialization and de-serialization.
-
-In order to avoid the overhead of re-validating all of the data in a node when
-one thing is updated (this can induce a lot of overhead), the stnode objects
-will attempt to parse a given "tagged-node's" schema down so that it is only
-validating the field being updated. It performs the validation by attempting to
-construct in-memory an ASDF-schema representing just the portion of the schema
-it needs to validate just that single field against.  It then passes that schema
-into the ASDF validation routines to check the data. Unfortunately, this is not
-a perfect process nor is it particularly robust. It is possible for a schema to
-have fields that the parse down process cannot handle, or use JSON-schema
-constructs which the parser is unaware of. In these cases, validation might
-raise an error or pass invalid data.
-
-.. warning::
-
-    The only validation process that is guaranteed to validate the data
-    correctly is the full ASDF validation process. This is because ASDF will be
-    using the full schema and be checking everything against it. The on-the-fly
-    validation's parsing may create unreliable validation scenarios.
-
-.. note::
-
-    In order to avoid the "on-the-fly" validation process, one can set values in
-    a node/datamodel via the dictionary, ``[]``, interface instead of the ``.``
-    interface. This is because the ``[]`` purposely bypasses the on-the-fly
-    validation process. Thus in general it is recommend that one uses the ``.``
-    interface for setting values in a node/datamodel, and only using the ``[]``
-    when one needs to store temporary invalid data in a node/datamodel. The use
-    ``[]`` runs the risk of placing the node/datamodel in a state where it
-    cannot be serialized to ASDF.
-
-
 ASDF
 ----
 

docs/roman_datamodels/datamodels/using_datamodels.rst

@@ -41,9 +41,10 @@ page::
     print(dm.meta.exposure.start_time_mjd)
     60000.0
 
-    # Try to assign invalid type
+    # Assign invalid type
 
     >>> d.meta.exposure.start_time_mjd = "hello"
+    >>> d.validate()
 
     # Last part of resulting traceback
 
@@ -72,13 +73,28 @@ page::
 
     # Try to assign wrong kind of node
 
-    >>> dm.meta.observation = dm.meta.exposure
-    Failed validating 'tag' in schema:
-        {'$schema': 'http://stsci.edu/schemas/asdf-schema/0.1.0/asdf-schema',
-         'tag': 'asdf://stsci.edu/datamodels/roman/tags/observation-1.0.0'}
-
-    On instance:
-        {'groupgap': 0, 'ma_table_name': 'High Latitude Spec. Survey', 'ma_table_number': 1, 'nframes': 8, 'ngroups': 6, 'p_exptype': 'WFI_IMAGE|', 'type': 'WFI_IMAGE'}
+    >>> dm.meta.exposure = dm.meta.observation
+    >>> dm.validate()
+
+    ValidationError: mismatched tags, wanted 'asdf://stsci.edu/datamodels/roman/tags/exposure-1.0.0', got 'asdf://stsci.edu/datamodels/roman/tags/observation-1.0.0'
+
+    Failed validating 'tag' in schema['properties']['meta']['allOf'][0]['allOf'][1]['properties']['exposure']:
+        {'tag': 'asdf://stsci.edu/datamodels/roman/tags/exposure-1.0.0',
+         'title': 'Exposure Information'}
+
+    On instance['meta']['exposure']:
+        {'execution_plan': 1,
+         'exposure': 1,
+         'observation': 1,
+         'observation_id': '?',
+         'pass': 1,
+         'program': 1,
+         'segment': 1,
+         'visit': 1,
+         'visit_file_activity': '01',
+         'visit_file_group': 1,
+         'visit_file_sequence': 1,
+         'visit_id': '?'}
 
     # Show and then change pixel value in data