diff --git a/lib/fhir_models/bootstrap/json.rb b/lib/fhir_models/bootstrap/json.rb
index 1b89395a..3a188ddb 100644
--- a/lib/fhir_models/bootstrap/json.rb
+++ b/lib/fhir_models/bootstrap/json.rb
@@ -1,16 +1,12 @@
 require 'json'
 
 module FHIR
-  module Json
+  module ClassJson
     #
     #  This module includes methods to serialize or deserialize FHIR resources to and from JSON.
     #
 
-    def to_json(opts = nil)
-      JSON.pretty_generate(to_hash, opts)
-    end
-
-    def self.from_json(json)
+    def from_json(json)
       hash = JSON.parse(json)
       resource = nil
       begin
@@ -24,13 +20,11 @@ def self.from_json(json)
       end
       resource
     end
+  end
 
-    def self.fhir_version_string
-      FHIR.fhir_version_string
-    end
-
-    def self.versioned_fhir_module
-      FHIR.versioned_fhir_module
+  module InstanceJson
+    def to_json(opts = nil)
+      JSON.pretty_generate(to_hash, opts)
     end
   end
 end
\ No newline at end of file
diff --git a/lib/fhir_models/bootstrap/xml.rb b/lib/fhir_models/bootstrap/xml.rb
index beb4972a..7892f432 100644
--- a/lib/fhir_models/bootstrap/xml.rb
+++ b/lib/fhir_models/bootstrap/xml.rb
@@ -1,75 +1,7 @@
 require 'nokogiri'
 module FHIR
-  module Xml
-    extend FHIR::Deprecate
-    #
-    #  This module includes methods to serialize or deserialize FHIR resources to and from XML.
-    #
-
-    def to_xml
-      hash = to_hash
-      hash.delete('resourceType')
-      doc = Nokogiri::XML::Document.new
-      doc.encoding = 'utf-8'
-      doc.root = hash_to_xml_node(resourceType, hash, doc)
-      doc.root.default_namespace = 'http://hl7.org/fhir'
-      doc.to_xml
-    end
-
-    # Hash keys are ordered in Ruby 1.9 and later, so we can rely on their order
-    # to be the correct order for the XML serialization.
-    def hash_to_xml_node(name, hash, doc)
-      node = Nokogiri::XML::Node.new(name, doc)
-
-      # if hash contains resourceType
-      # create a child node with the name==resourceType
-      # fill that, and place the child under the above `node`
-      if hash['resourceType'].is_a?(String) && name != 'instance'
-        child_name = hash['resourceType']
-        hash.delete('resourceType')
-        child = hash_to_xml_node(child_name, hash, doc)
-        node.add_child(child)
-        return node
-      end
-
-      hash.each do |key, value|
-        next if ['extension', 'modifierExtension'].include?(name) && key == 'url'
-        next if key == 'id' && !versioned_fhir_module::RESOURCES.include?(name)
-
-        case value
-        when Hash
-          node.add_child(hash_to_xml_node(key, value, doc))
-        when Array
-          value.each do |v|
-            if v.is_a?(Hash)
-              node.add_child(hash_to_xml_node(key, v, doc))
-            else
-              child = Nokogiri::XML::Node.new(key, doc)
-              child.set_attribute('value', v)
-              node.add_child(child)
-            end
-          end
-        else
-          child = Nokogiri::XML::Node.new(key, doc)
-          if name == 'text' && key == 'div'
-            child.set_attribute('xmlns', 'http://www.w3.org/1999/xhtml')
-            html = value.strip
-            if html.start_with?('<div') && html.end_with?('</div>')
-              html = html[html.index('>') + 1..-7]
-            end
-            child.inner_html = html
-          else
-            child.set_attribute('value', value)
-          end
-          node.add_child(child)
-        end
-      end
-      node.set_attribute('url', hash['url']) if ['extension', 'modifierExtension'].include?(name)
-      node.set_attribute('id', hash['id']) if hash['id'] && !versioned_fhir_module::RESOURCES.include?(name)
-      node
-    end
-
-    def self.from_xml(xml)
+  module ClassXml
+    def from_xml(xml)
       doc = Nokogiri::XML(xml)
       doc.root.add_namespace_definition('f', 'http://hl7.org/fhir')
       doc.root.add_namespace_definition('x', 'http://www.w3.org/1999/xhtml')
@@ -88,7 +20,7 @@ def self.from_xml(xml)
       resource
     end
 
-    def self.xml_node_to_hash(node)
+    def xml_node_to_hash(node)
       hash = {}
       node.children.each do |child|
         next if [Nokogiri::XML::Text, Nokogiri::XML::Comment].include?(child.class)
@@ -126,27 +58,84 @@ def self.xml_node_to_hash(node)
       end
     end
 
-    def self.valid?(xml)
+    def valid?(xml)
       validate(xml).empty?
     end
-    deprecate :is_valid?, :valid?
 
-    def self.validate(xml)
+    def validate(xml)
       defns = File.expand_path '../definitions/schema', File.dirname(File.absolute_path(__FILE__))
       schema = File.join(defns, 'fhir-all.xsd')
       xsd = Nokogiri::XML::Schema(File.new(schema))
       xsd.validate(Nokogiri::XML(xml))
     end
+  end
 
-    def self.fhir_version_string
-      FHIR.fhir_version_string
-    end
+  module InstanceXml
+    #
+    #  This module includes methods to serialize or deserialize FHIR resources to and from XML.
+    #
 
-    def self.versioned_fhir_module
-      FHIR.versioned_fhir_module
+    def to_xml
+      hash = to_hash
+      hash.delete('resourceType')
+      doc = Nokogiri::XML::Document.new
+      doc.encoding = 'utf-8'
+      doc.root = hash_to_xml_node(resourceType, hash, doc)
+      doc.root.default_namespace = 'http://hl7.org/fhir'
+      doc.to_xml
     end
 
-    private :hash_to_xml_node
-    private_class_method :xml_node_to_hash
+    # Hash keys are ordered in Ruby 1.9 and later, so we can rely on their order
+    # to be the correct order for the XML serialization.
+    def hash_to_xml_node(name, hash, doc)
+      node = Nokogiri::XML::Node.new(name, doc)
+
+      # if hash contains resourceType
+      # create a child node with the name==resourceType
+      # fill that, and place the child under the above `node`
+      if hash['resourceType'].is_a?(String) && name != 'instance'
+        child_name = hash['resourceType']
+        hash.delete('resourceType')
+        child = hash_to_xml_node(child_name, hash, doc)
+        node.add_child(child)
+        return node
+      end
+
+      hash.each do |key, value|
+        next if ['extension', 'modifierExtension'].include?(name) && key == 'url'
+        next if key == 'id' && !versioned_fhir_module::RESOURCES.include?(name)
+
+        case value
+        when Hash
+          node.add_child(hash_to_xml_node(key, value, doc))
+        when Array
+          value.each do |v|
+            if v.is_a?(Hash)
+              node.add_child(hash_to_xml_node(key, v, doc))
+            else
+              child = Nokogiri::XML::Node.new(key, doc)
+              child.set_attribute('value', v)
+              node.add_child(child)
+            end
+          end
+        else
+          child = Nokogiri::XML::Node.new(key, doc)
+          if name == 'text' && key == 'div'
+            child.set_attribute('xmlns', 'http://www.w3.org/1999/xhtml')
+            html = value.strip
+            if html.start_with?('<div') && html.end_with?('</div>')
+              html = html[html.index('>') + 1..-7]
+            end
+            child.inner_html = html
+          else
+            child.set_attribute('value', value)
+          end
+          node.add_child(child)
+        end
+      end
+      node.set_attribute('url', hash['url']) if ['extension', 'modifierExtension'].include?(name)
+      node.set_attribute('id', hash['id']) if hash['id'] && !versioned_fhir_module::RESOURCES.include?(name)
+      node
+    end
   end
 end
diff --git a/lib/fhir_models/r4.rb b/lib/fhir_models/r4.rb
index 11915302..7367d044 100644
--- a/lib/fhir_models/r4.rb
+++ b/lib/fhir_models/r4.rb
@@ -45,12 +45,14 @@
 
 module FHIR
   module R4
-    def self.fhir_version_string
+    module_function
+
+    def fhir_version_string
       'R4'
     end
 
-    def self.versioned_fhir_module
-      self
+    def versioned_fhir_module
+      FHIR::R4
     end
   end
 end
diff --git a/lib/fhir_models/r4/fhir_ext/element_definition.rb b/lib/fhir_models/r4/fhir_ext/element_definition.rb
deleted file mode 100644
index a18b505d..00000000
--- a/lib/fhir_models/r4/fhir_ext/element_definition.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-module FHIR
-  module R4
-    class ElementDefinition < Model
-      include FHIR::CommonElementDefinition
-
-      def self.fhir_version_string
-        'R4'
-      end
-
-      def self.versioned_fhir_module
-        FHIR::R4
-      end
-    end
-  end
-
-  ElementDefinition = FHIR::R4::ElementDefinition
-end
diff --git a/lib/fhir_models/r4/fhir_ext/structure_definition.rb b/lib/fhir_models/r4/fhir_ext/structure_definition.rb
deleted file mode 100644
index 35abeb35..00000000
--- a/lib/fhir_models/r4/fhir_ext/structure_definition.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-module FHIR
-  module R4
-    class StructureDefinition
-      include FHIR::CommonStructureDefinition
-
-      def self.fhir_version_string
-        'R4'
-      end
-
-      def self.versioned_fhir_module
-        FHIR::R4
-      end
-    end
-  end
-
-  StructureDefinition = FHIR::R4::StructureDefinition
-end
\ No newline at end of file
diff --git a/lib/fhir_models/r4b.rb b/lib/fhir_models/r4b.rb
index c5b8c859..b5a3e404 100644
--- a/lib/fhir_models/r4b.rb
+++ b/lib/fhir_models/r4b.rb
@@ -45,12 +45,14 @@
 
 module FHIR
   module R4B
-    def self.fhir_version_string
+    module_function
+
+    def fhir_version_string
       'R4B'
     end
 
-    def self.versioned_fhir_module
-      self
+    def versioned_fhir_module
+      FHIR::R4B
     end
   end
 end
diff --git a/lib/fhir_models/r4b/fhir_ext/element_definition.rb b/lib/fhir_models/r4b/fhir_ext/element_definition.rb
deleted file mode 100644
index fdcc5826..00000000
--- a/lib/fhir_models/r4b/fhir_ext/element_definition.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-module FHIR
-  module R4B
-    class ElementDefinition < Model
-      include CommonElementDefinition
-
-      def self.fhir_version_string
-        'R4B'
-      end
-
-      def self.versioned_fhir_module
-        FHIR::R4B
-      end
-    end
-  end
-end
diff --git a/lib/fhir_models/r4b/fhir_ext/structure_definition.rb b/lib/fhir_models/r4b/fhir_ext/structure_definition.rb
deleted file mode 100644
index beeeb12e..00000000
--- a/lib/fhir_models/r4b/fhir_ext/structure_definition.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-module FHIR
-  module R4B
-    class StructureDefinition
-      include CommonStructureDefinition
-
-      def self.fhir_version_string
-        'R4B'
-      end
-
-      def self.versioned_fhir_module
-        FHIR::R4B
-      end
-    end
-  end
-end
\ No newline at end of file