diff --git a/lib/jsi/base.rb b/lib/jsi/base.rb
index 2b655e5f..6007c3f4 100644
--- a/lib/jsi/base.rb
+++ b/lib/jsi/base.rb
@@ -220,7 +220,7 @@ def jsi_each_descendent_node(propertyNames: false, &block)
       end
 
       jsi_each_child_token do |token|
-        jsi_child(token, as_jsi: true).jsi_each_descendent_node(propertyNames: propertyNames, &block)
+        jsi_child_node(token).jsi_each_descendent_node(propertyNames: propertyNames, &block)
       end
 
       nil
@@ -239,7 +239,7 @@ def jsi_select_descendents_node_first(&block)
         if jsi_array? || jsi_hash?
           res = instance.class.new
           jsi_each_child_token do |token|
-            v = jsi_child(token, as_jsi: true)
+            v = jsi_child_node(token)
             if yield(v)
               res_v = v.jsi_select_descendents_node_first(&block).jsi_node_content
               if jsi_array?
@@ -269,7 +269,7 @@ def jsi_select_descendents_leaf_first(&block)
         if jsi_array? || jsi_hash?
           res = instance.class.new
           jsi_each_child_token do |token|
-            v = jsi_child(token, as_jsi: true).jsi_select_descendents_leaf_first(&block)
+            v = jsi_child_node(token).jsi_select_descendents_leaf_first(&block)
             if yield(v)
               res_v = v.jsi_node_content
               if jsi_array?
@@ -294,7 +294,7 @@ def jsi_parent_nodes
 
       jsi_ptr.tokens.map do |token|
         parent.tap do
-          parent = parent[token, as_jsi: true]
+          parent = parent.jsi_child_node(token)
         end
       end.reverse!.freeze
     end
@@ -315,7 +315,7 @@ def jsi_ancestor_nodes
       ancestors << ancestor
 
       jsi_ptr.tokens.each do |token|
-        ancestor = ancestor[token, as_jsi: true]
+        ancestor = ancestor.jsi_child_node(token)
         ancestors << ancestor
       end
       ancestors.reverse!.freeze
@@ -408,6 +408,12 @@ def jsi_child(token, as_jsi: )
     end
     private :jsi_child # internals for #[] but idk, could be public
 
+    # @param token (see Base#[])
+    # @return [JSI::Base]
+    protected def jsi_child_node(token)
+      jsi_child(token, as_jsi: true)
+    end
+
     # A default value for a child of this node identified by the given token, if schemas describing
     # that child define a default value.
     #
@@ -437,7 +443,7 @@ def jsi_default_child(token, as_jsi: )
         jsi_child_as_jsi(defaults.first, child_applied_schemas, as_jsi) do
           jsi_modified_copy do |i|
             i.dup.tap { |i_dup| i_dup[token] = defaults.first }
-          end[token, as_jsi: true]
+          end.jsi_child_node(token)
         end
       else
         child_content
diff --git a/lib/jsi/base/node.rb b/lib/jsi/base/node.rb
index 497b66a3..e5898eca 100644
--- a/lib/jsi/base/node.rb
+++ b/lib/jsi/base/node.rb
@@ -98,7 +98,7 @@ def as_json(options = {})
           k.is_a?(Symbol) ? k.to_s :
           k.respond_to?(:to_str) && (kstr = k.to_str).is_a?(String) ? kstr :
           raise(TypeError, "JSON object (Hash) cannot be keyed with: #{k.pretty_inspect.chomp}")
-        hash[ks] = jsi_child(k, as_jsi: true).as_json(**options)
+        hash[ks] = jsi_child_node(k).as_json(**options)
       end
       hash
     end
@@ -263,7 +263,7 @@ def to_ary(**kw)
 
     # See {Base#as_json}
     def as_json(options = {})
-      each_index.map { |i| jsi_child(i, as_jsi: true).as_json(**options) }
+      each_index.map { |i| jsi_child_node(i).as_json(**options) }
     end
 
     include Util::Arraylike
diff --git a/lib/jsi/jsi_coder.rb b/lib/jsi/jsi_coder.rb
index cccdafb5..e78c9f9a 100644
--- a/lib/jsi/jsi_coder.rb
+++ b/lib/jsi/jsi_coder.rb
@@ -31,7 +31,7 @@ class JSICoder
     #   or an array of them. note that it may be preferable to simply use an array schema.
     # @param jsi_opt [Hash] keyword arguments to pass to {Schema#new_jsi} when loading
     # @param as_json_opt [Hash] keyword arguments to pass to `#as_json` when dumping
-    def initialize(schema, array: false, jsi_opt: {}, as_json_opt: {})
+    def initialize(schema, array: false, jsi_opt: Util::EMPTY_HASH, as_json_opt: Util::EMPTY_HASH)
       unless schema.respond_to?(:new_jsi)
         raise(ArgumentError, "schema param does not respond to #new_jsi: #{schema.inspect}")
       end
diff --git a/lib/jsi/metaschema_node.rb b/lib/jsi/metaschema_node.rb
index 5983d09a..96b491f4 100644
--- a/lib/jsi/metaschema_node.rb
+++ b/lib/jsi/metaschema_node.rb
@@ -229,7 +229,7 @@ def our_initialize_params
         jsi_schema_base_uri: jsi_schema_base_uri,
         jsi_schema_registry: jsi_schema_registry,
         jsi_content_to_immutable: jsi_content_to_immutable,
-      }
+      }.freeze
     end
 
     # note: not for root node
diff --git a/lib/jsi/ptr.rb b/lib/jsi/ptr.rb
index 33f3c5f2..38f14263 100644
--- a/lib/jsi/ptr.rb
+++ b/lib/jsi/ptr.rb
@@ -167,19 +167,25 @@ def parent
         tokens.size == 1 ? EMPTY : Ptr.new(tokens[0...-1].freeze)
       end
 
-      # whether this pointer contains the other_ptr - that is, whether this pointer is an ancestor
-      # of `other_ptr`, a descendent pointer. `contains?` is inclusive; a pointer does contain itself.
+      # whether this pointer is an ancestor of `other_ptr`, a descendent pointer.
+      # `ancestor_of?` is inclusive; a pointer is an ancestor of itself.
+      #
       # @return [Boolean]
-      def contains?(other_ptr)
+      def ancestor_of?(other_ptr)
         tokens == other_ptr.tokens[0...tokens.size]
       end
 
+      # @deprecated
+      def contains?(other_ptr)
+        ancestor_of?(other_ptr)
+      end
+
       # part of this pointer relative to the given ancestor_ptr
       # @return [JSI::Ptr]
       # @raise [JSI::Ptr::Error] if the given ancestor_ptr is not an ancestor of this pointer
       def relative_to(ancestor_ptr)
         return self if ancestor_ptr.empty?
-        unless ancestor_ptr.contains?(self)
+        unless ancestor_ptr.ancestor_of?(self)
           raise(Error, "ancestor_ptr #{ancestor_ptr.inspect} is not ancestor of #{inspect}")
         end
         ancestor_ptr.tokens.size == tokens.size ? EMPTY : Ptr.new(tokens[ancestor_ptr.tokens.size..-1].freeze)
diff --git a/lib/jsi/schema.rb b/lib/jsi/schema.rb
index 2448b59a..66a39d29 100644
--- a/lib/jsi/schema.rb
+++ b/lib/jsi/schema.rb
@@ -376,16 +376,17 @@ def ensure_schema(schema, msg: "indicated object is not a schema:", reinstantiat
           if reinstantiate_as && schema.is_a?(JSI::Base)
             # TODO warn; behavior is undefined and I hate this implementation
 
-            result_schema_schemas = schema.jsi_schemas + reinstantiate_as
+            result_schema_indicated_schemas = SchemaSet.new(schema.jsi_indicated_schemas + reinstantiate_as)
+            result_schema_applied_schemas = result_schema_indicated_schemas.inplace_applicator_schemas(schema.jsi_node_content)
 
-            result_schema_class = JSI::SchemaClasses.class_for_schemas(result_schema_schemas,
+            result_schema_class = JSI::SchemaClasses.class_for_schemas(result_schema_applied_schemas,
               includes: SchemaClasses.includes_for(schema.jsi_node_content),
               mutable: schema.jsi_mutable?,
             )
 
             result_schema_class.new(schema.jsi_document,
               jsi_ptr: schema.jsi_ptr,
-              jsi_indicated_schemas: schema.jsi_indicated_schemas,
+              jsi_indicated_schemas: result_schema_indicated_schemas,
               jsi_schema_base_uri: schema.jsi_schema_base_uri,
               jsi_schema_resource_ancestors: schema.jsi_schema_resource_ancestors,
               jsi_schema_registry: schema.jsi_schema_registry,
@@ -466,7 +467,7 @@ def schema_absolute_uri
     end
 
     # a nonrelative URI which refers to this schema.
-    # nil if no parent of this schema defines an id.
+    # `nil` if no ancestor of this schema defines an id.
     # see {#schema_uris} for all URIs known to refer to this schema.
     # @return [Addressable::URI, nil]
     def schema_uri
@@ -491,22 +492,22 @@ def each_schema_uri
 
       yield schema_absolute_uri if schema_absolute_uri
 
-      parent_schemas = jsi_subschema_resource_ancestors.reverse_each.select do |resource|
+      ancestor_schemas = jsi_subschema_resource_ancestors.reverse_each.select do |resource|
         resource.schema_absolute_uri
       end
 
       anchored = respond_to?(:anchor) ? anchor : nil
-      parent_schemas.each do |parent_schema|
+      ancestor_schemas.each do |ancestor_schema|
         if anchored
-          if parent_schema.jsi_anchor_subschema(anchor) == self
-            yield parent_schema.schema_absolute_uri.merge(fragment: anchor).freeze
+          if ancestor_schema.jsi_anchor_subschema(anchor) == self
+            yield(ancestor_schema.schema_absolute_uri.merge(fragment: anchor).freeze)
           else
             anchored = false
           end
         end
 
-        relative_ptr = jsi_ptr.relative_to(parent_schema.jsi_ptr)
-        yield parent_schema.schema_absolute_uri.merge(fragment: relative_ptr.fragment).freeze
+        relative_ptr = jsi_ptr.relative_to(ancestor_schema.jsi_ptr)
+        yield(ancestor_schema.schema_absolute_uri.merge(fragment: relative_ptr.fragment).freeze)
       end
 
       nil
@@ -603,10 +604,10 @@ def describes_schema!(schema_implementation_modules)
 
     # a resource containing this schema.
     #
-    # if any parent, or this schema itself, is a schema with an absolute uri (see {#schema_absolute_uri}),
+    # If any ancestor, or this schema itself, is a schema with an absolute uri (see {#schema_absolute_uri}),
     # the resource root is the closest schema with an absolute uri.
     #
-    # If no parent schema has an absolute uri, the schema_resource_root is the {Base#jsi_root_node document's root node}.
+    # If no ancestor schema has an absolute uri, the schema_resource_root is the {Base#jsi_root_node document's root node}.
     # In this case, the resource root may or may not be a schema itself.
     #
     # @return [JSI::Base] resource containing this schema
@@ -767,7 +768,14 @@ def internal_validate_instance(
       else
         result = JSI::Validation::FullResult.new
       end
-      result_builder = result.builder(self, instance_ptr, instance_document, validate_only, visited_refs)
+      result_builder = result.class::Builder.new(
+        result: result,
+        schema: self,
+        instance_ptr: instance_ptr,
+        instance_document: instance_document,
+        validate_only: validate_only,
+        visited_refs: visited_refs,
+      )
 
       catch(:jsi_validation_result) do
         # note: true/false are not valid as schemas in draft 4; they are only values of
diff --git a/lib/jsi/schema/schema_ancestor_node.rb b/lib/jsi/schema/schema_ancestor_node.rb
index 4291ce37..9cd247e6 100644
--- a/lib/jsi/schema/schema_ancestor_node.rb
+++ b/lib/jsi/schema/schema_ancestor_node.rb
@@ -18,7 +18,7 @@ def initialize(*, **)
 
     # the base URI used to resolve the ids of schemas at or below this JSI.
     # this is always an absolute URI (with no fragment).
-    # this may be the absolute schema URI of a parent schema or the URI from which the document was retrieved.
+    # This may be the absolute schema URI of an ancestor schema or the URI from which the document was retrieved.
     # @api private
     # @return [Addressable::URI, nil]
     attr_reader :jsi_schema_base_uri
@@ -34,7 +34,7 @@ def initialize(*, **)
 
     # the URI of the resource containing this node.
     # this is always an absolute URI (with no fragment).
-    # if this node is a schema with an id, this is its absolute URI; otherwise a parent resource's URI,
+    # If this node is a schema with an id, this is its absolute URI; otherwise an ancestor resource's URI,
     # or nil if not contained by a resource with a URI.
     # @return [Addressable::URI, nil]
     def jsi_resource_ancestor_uri
@@ -97,7 +97,7 @@ def jsi_schema_resource_ancestors=(jsi_schema_resource_ancestors)
       #chkbug   end
       #chkbug   if anc.jsi_ptr == jsi_ptr
       #chkbug     raise(Bug, "ancestor is self")
-      #chkbug   elsif !anc.jsi_ptr.contains?(jsi_ptr)
+      #chkbug   elsif !anc.jsi_ptr.ancestor_of?(jsi_ptr)
       #chkbug     raise(Bug, "ancestor does not contain self")
       #chkbug   end
       #chkbug   last_anc_ptr = anc.jsi_ptr
diff --git a/lib/jsi/schema_set.rb b/lib/jsi/schema_set.rb
index dfdef5a5..4951b83e 100644
--- a/lib/jsi/schema_set.rb
+++ b/lib/jsi/schema_set.rb
@@ -6,14 +6,12 @@ module JSI
   # any schema instance is described by a set of schemas.
   class SchemaSet < ::Set
     class << self
-      # builds a SchemaSet from a mutable Set which is added to by the given block
+      # Builds a SchemaSet, yielding a yielder to be called with each schema of the SchemaSet.
       #
-      # @yield [Set] a Set to which the block may add schemas
+      # @yield [Enumerator::Yielder]
       # @return [SchemaSet]
-      def build
-        mutable_set = Set.new
-        yield mutable_set
-        new(mutable_set)
+      def build(&block)
+        new(Enumerator.new(&block))
       end
 
       # ensures the given param becomes a SchemaSet. returns the param if it is already SchemaSet, otherwise
@@ -192,8 +190,9 @@ def each_child_applicator_schema(token, instance, &block)
     # @param instance [Object] the instance to validate against our schemas
     # @return [JSI::Validation::Result]
     def instance_validate(instance)
-      results = map { |schema| schema.instance_validate(instance) }
-      results.inject(Validation::FullResult.new, &:merge).freeze
+      inject(Validation::FullResult.new) do |result, schema|
+        result.merge(schema.instance_validate(instance))
+      end.freeze
     end
 
     # whether the given instance is valid against our schemas
diff --git a/lib/jsi/simple_wrap.rb b/lib/jsi/simple_wrap.rb
index 9ce77a7d..d9eac6a4 100644
--- a/lib/jsi/simple_wrap.rb
+++ b/lib/jsi/simple_wrap.rb
@@ -15,7 +15,7 @@ def internal_validate_keywords(result_builder)
   end
 
   simple_wrap_metaschema = JSI.new_metaschema(nil, schema_implementation_modules: [simple_wrap_implementation])
-  SimpleWrap = simple_wrap_metaschema.new_schema_module({})
+  SimpleWrap = simple_wrap_metaschema.new_schema_module(Util::EMPTY_HASH)
 
   # SimpleWrap is a JSI schema module which recursively wraps nested structures
   module SimpleWrap
diff --git a/lib/jsi/util/private.rb b/lib/jsi/util/private.rb
index 68ba26c3..677949ba 100644
--- a/lib/jsi/util/private.rb
+++ b/lib/jsi/util/private.rb
@@ -12,6 +12,8 @@ module Util::Private
 
     EMPTY_ARY = [].freeze
 
+    EMPTY_HASH = {}.freeze
+
     EMPTY_SET = Set[].freeze
 
     CLASSES_ALWAYS_FROZEN = Set[TrueClass, FalseClass, NilClass, Integer, Float, BigDecimal, Rational, Symbol].freeze
@@ -179,24 +181,5 @@ def freeze
         super
       end
     end
-
-    module Virtual
-      class InstantiationError < StandardError
-      end
-
-      # this virtual class is not intended to be instantiated except by its subclasses, which override #initialize
-      def initialize
-        # :nocov:
-        raise(InstantiationError, "cannot instantiate virtual class #{self.class}")
-        # :nocov:
-      end
-
-      # virtual_method is used to indicate that the method calling it must be implemented on the (non-virtual) subclass
-      def virtual_method
-        # :nocov:
-        raise(Bug, "class #{self.class} must implement #{caller_locations.first.label}")
-        # :nocov:
-      end
-    end
   end
 end
diff --git a/lib/jsi/validation/error.rb b/lib/jsi/validation/error.rb
index fe8f39ac..045ecbd3 100644
--- a/lib/jsi/validation/error.rb
+++ b/lib/jsi/validation/error.rb
@@ -29,6 +29,10 @@ module Validation
     #   document containing the instance at instance_ptr
     #   @return [Object]
     class Error
+      def initialize(attributes = {})
+        super
+        freeze
+      end
     end
   end
 end
diff --git a/lib/jsi/validation/result.rb b/lib/jsi/validation/result.rb
index 80847215..3b7fed51 100644
--- a/lib/jsi/validation/result.rb
+++ b/lib/jsi/validation/result.rb
@@ -3,10 +3,7 @@
 module JSI
   module Validation
     # a result of validating an instance against schemas which describe it.
-    # virtual base class.
     class Result
-      include Util::Virtual
-
       Builder = Util::AttrStruct[*%w(
         result
         schema
@@ -24,7 +21,6 @@ def instance
         end
 
         def schema_issue(*_)
-          virtual_method
         end
 
         def schema_error(message, keyword = nil)
@@ -74,23 +70,10 @@ def merge_schema_issues(other_result)
     end
 
     class Result
-      def builder(schema, instance_ptr, instance_document, validate_only, visited_refs)
-        self.class::Builder.new(
-          result: self,
-          schema: schema,
-          instance_ptr: instance_ptr,
-          instance_document: instance_document,
-          validate_only: validate_only,
-          visited_refs: visited_refs,
-        )
-      end
-
       # is the instance valid against its schemas?
       # @return [Boolean]
       def valid?
-        # :nocov:
-        virtual_method
-        # :nocov:
+        #dbg raise(NotImplementedError)
       end
 
       include Util::FingerprintHash
@@ -144,7 +127,6 @@ def valid?
       end
 
       def freeze
-        @validation_errors.each(&:freeze)
         @schema_issues.each(&:freeze)
         @validation_errors.freeze
         @schema_issues.freeze
@@ -160,10 +142,6 @@ def merge(result)
         self
       end
 
-      def +(result)
-        FullResult.new.merge(self).merge(result)
-      end
-
       # see {Util::Private::FingerprintHash}
       # @api private
       def jsi_fingerprint
diff --git a/test/metaschema_node_test.rb b/test/metaschema_node_test.rb
index d1136dc8..867357c7 100644
--- a/test/metaschema_node_test.rb
+++ b/test/metaschema_node_test.rb
@@ -301,7 +301,7 @@ def assert_metaschema_behaves
         metaschema.instance_validate(metaschema),
       ]
       metaschema.jsi_each_descendent_node do |node|
-        if node.jsi_ptr.contains?(JSI::Ptr['title'])
+        if node.jsi_ptr.ancestor_of?(JSI::Ptr['title'])
           results << node.jsi_validate
         else
           assert(node.jsi_valid?)