diff --git a/External/optional/optional.hpp b/External/optional/optional.hpp
diff --git a/Foundation/Common.h b/Foundation/Common.h
@@ -5,17 +5,27 @@
 #include <string>
 #include <unordered_map>
 
-#include <stdint.h>
-#include <enum/enum.h>
+#include <cstdint>
 
-typedef const char *(*annotation_f)();
+#include <enum\enum.h>
+#include <optional\optional.hpp>
+
+
+template <class T>
+using Optional = nonstd::optional<T>;
 
 using RString = std::string;
 using RFile = std::string;
 using RHash = uint32_t;
 
+#include "Foundation\Reflection\ReflectionList.h"
+#include "Foundation\Reflection\ReflectionMap.h"
+
+template <class T>
+using RList = RArrayList<T>;
+
 template <class T>
-using RList = std::vector<T>;
+using RDictionary = ReflectionMap<std::string, T>;
 
 template <class T>
-using RDictionary = std::unordered_map<RHash, T>;
+using RHashMap = ReflectionMap<RHash, T>;
diff --git a/Foundation/Foundation.vcxproj b/Foundation/Foundation.vcxproj
@@ -27,8 +27,9 @@
     <ClInclude Include="Document\DocumentPath.h" />
     <ClInclude Include="Json\Json.h" />
     <ClInclude Include="Reflection\Reflection.h" />
-    <ClInclude Include="Reflection\ReflectionArray.h" />
     <ClInclude Include="Reflection\ReflectionJson.h" />
+    <ClInclude Include="Reflection\ReflectionList.h" />
+    <ClInclude Include="Reflection\ReflectionMap.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="Document\Document.cpp" />

diff --git a/Foundation/Foundation.vcxproj.filters b/Foundation/Foundation.vcxproj.filters
@@ -31,7 +31,10 @@
     <ClInclude Include="Json\Json.h">
       <Filter>Json</Filter>
     </ClInclude>
-    <ClInclude Include="Reflection\ReflectionArray.h">
+    <ClInclude Include="Reflection\ReflectionMap.h">
+      <Filter>Reflection</Filter>
+    </ClInclude>
+    <ClInclude Include="Reflection\ReflectionList.h">
       <Filter>Reflection</Filter>
     </ClInclude>
   </ItemGroup>

diff --git a/Foundation/Reflection/ReflectionJson.h b/Foundation/Reflection/ReflectionJson.h
@@ -30,16 +30,16 @@ void DecodeJson(T & value, Json & j)
 }
 
 template <class T>
-void DecodeJson(RList<T> & value, Json & j)
+void DecodeJson(RArrayList<T> & value, Json & j)
 {
-  value.clear();
-  value.reserve(j.size());
+  value.Clear();
+  value.Reserve(j.size());
   for (auto t : j)
   {
     T new_val;
     DecodeJson(new_val, t);
 
-    value.push_back(new_val);
+    value.PushBack(new_val);
   }
 }
 
@@ -134,7 +134,7 @@ Json EncodeJson(const T & value)
 }
 
 template <class T>
-Json EncodeJson(const RList<T> & value)
+Json EncodeJson(const RArrayList<T> & value)
 {
   Json j_value;
   for (auto t : value)

diff --git a/Foundation/Reflection/ReflectionArray.h → Foundation/Reflection/ReflectionList.h b/Foundation/Reflection/ReflectionArray.h → Foundation/Reflection/ReflectionList.h
@@ -2,6 +2,77 @@
 
 #include "Foundation\Common.h"
 
+template <class T>
+class RArrayList
+{
+public:
+
+  void Clear()
+  {
+    m_Values.clear();
+  }
+
+  void Reserve(std::size_t size)
+  {
+    m_Values.reserve(size);
+  }
+
+  void PushBack(const T & val)
+  {
+    m_Values.push_back(val);
+  }
+
+  void InsertAt(const T & val, std::size_t logical_index)
+  {
+    if (logical_index == m_Values.size())
+    {
+      m_Values.push_back(ContainerData());
+      return;
+    }
+
+    m_Values.insert(m_Values.begin() + logical_index);
+  }
+
+  void RemoveAt(std::size_t logical_index)
+  {
+    m_Values.erase(m_Values.begin() + logical_index);
+  }
+
+  std::size_t HighestIndex()
+  {
+    return m_Values.size();
+  }
+
+  void Compress()
+  {
+  }
+
+  auto begin()
+  {
+    return m_Values.begin();
+  }
+
+  auto end()
+  {
+    return m_Values.end();
+  }
+
+  auto begin() const
+  {
+    return m_Value.begin();
+  }
+
+  auto end() const
+  {
+    return m_Values.end();
+  }
+
+private:
+
+  std::vector<T> m_Values;
+};
+
+
 template <class T>
 class RSparseList
 {
@@ -21,9 +92,9 @@ class RSparseList
       return m_PhysicalIndex != rhs.m_PhysicalIndex;
     }
 
-    const std::pair<int, T &> operator *() const
+    const std::pair<std::size_t, T &> operator *() const
     {
-      std::pair<int, T &> val(m_PhysicalIndex, m_List->m_Values[m_PhysicalIndex].m_T);
+      std::pair<std::size_t, T &> val(m_PhysicalIndex, m_List->m_Values[m_PhysicalIndex].m_T);
       return val;
     }
 
@@ -37,7 +108,7 @@ class RSparseList
 
   private:
 
-    RSparseListIterator(RSparseList<T> * list, int physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
+    RSparseListIterator(RSparseList<T> * list, std::size_t physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
 
     std::size_t m_PhysicalIndex = 0;
     RSparseList<T> * m_List;
@@ -59,9 +130,9 @@ class RSparseList
       return m_PhysicalIndex != rhs.m_PhysicalIndex;
     }
 
-    const std::pair<int, const T &> operator *() const
+    const std::pair<std::size_t, const T &> operator *() const
     {
-      std::pair<int, const T &> val(m_PhysicalIndex, m_List->m_Values[m_PhysicalIndex].m_T);
+      std::pair<std::size_t, const T &> val(m_PhysicalIndex, m_List->m_Values[m_PhysicalIndex].m_T);
       return val;
     }
 
@@ -75,7 +146,7 @@ class RSparseList
 
   private:
 
-    RSparseListIteratorConst(const RSparseList<T> * list, int physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
+    RSparseListIteratorConst(const RSparseList<T> * list, std::size_t physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
 
     std::size_t m_PhysicalIndex = 0;
     const RSparseList<T> * m_List;
@@ -120,7 +191,7 @@ class RSparseList
 
     if (m_HighestIndex == logical_index)
     {
-      for (int index = m_Values.size() - 1; index >= 0 && m_Values[index].m_Valid == false; index--)
+      for (std::size_t index = m_Values.size() - 1; index >= 0 && m_Values[index].m_Valid == false; index--)
       {
         m_HighestIndex--;
       }
@@ -184,7 +255,6 @@ class RSparseList
     return itr;
   }
 
-
 private:
   struct ContainerData
   {
@@ -239,7 +309,7 @@ class RMergeList
 
   private:
 
-    RMergeListIterator(RMergeList<T> * list, int physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
+    RMergeListIterator(RMergeList<T> * list, std::size_t physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
 
     int m_PhysicalIndex = 0;
     RMergeList<T> * m_List;
@@ -274,7 +344,7 @@ class RMergeList
 
   private:
 
-    RMergeListIteratorConst(const RMergeList<T> * list, int physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
+    RMergeListIteratorConst(const RMergeList<T> * list, std::size_t physical_index) : m_List(list), m_PhysicalIndex(physical_index) { }
 
     int m_PhysicalIndex = 0;
     const RMergeList<T> * m_List;

diff --git a/Foundation/Reflection/ReflectionMap.h b/Foundation/Reflection/ReflectionMap.h
@@ -0,0 +1,68 @@
+#pragma once
+
+#include "Foundation\Common.h"
+
+template <class K, class T>
+class ReflectionMap
+{
+public:
+  void Clear()
+  {
+    m_Values.clear();
+  }
+
+  void Set(const K & k, T && t)
+  {
+    m_Values.insert_or_assign(k, t);
+  }
+
+  void Remove(const K & k)
+  {
+    auto itr = m_Values.find(k);
+    if (itr == m_Values.end())
+    {
+      return;
+    }
+
+    m_Values.erase(itr);
+  }
+
+  Optional<T> Get(const K & k)
+  {
+    auto itr = m_Values.find(k);
+    if (itr == m_Values.end())
+    {
+      return Optional<T>();
+    }
+
+    return itr->second;
+  }
+
+  T & operator [] (const K & k)
+  {
+    return m_Values[k];
+  }
+
+  auto begin()
+  {
+    return m_Values.begin();
+  }
+
+  auto end()
+  {
+    return m_Values.end();
+  }
+
+  auto begin() const
+  {
+    return m_Values.begin();
+  }
+
+  auto end() const
+  {
+    return m_Values.end();
+  }
+
+public:
+  std::unordered_map<uint32_t, T> m_Values;
+};
diff --git a/UnitTests/UnitTests.cpp b/UnitTests/UnitTests.cpp
@@ -5,7 +5,6 @@
 
 #include "Foundation\Common.h"
 #include "Foundation\Reflection\Reflection.h"
-#include "Foundation\Reflection\ReflectionArray.h"
 #include "Foundation\Reflection\ReflectionJson.h"
 
 #include "Foundation\Document\DocumentPath.h"
@@ -16,7 +15,7 @@ struct Inventory
 {
   Inventory()
   {
-    items.push_back(20);
+    items.PushBack(20);
   }
 
 public:
@@ -143,6 +142,11 @@ int main()
   asdf.RemoveAt(1);
   asdf.PushBack(90);
 
+  RHashMap<int> map;
+  map.Set(0, 2);
+  map.Get(0);
+  map.Remove(0);
+
   Json j = EncodeJson(asdf);
   std::string test = j.dump(2);
   std::cout << test << std::endl;