diff --git a/include/yaml-cpp/value/detail/node.h b/include/yaml-cpp/value/detail/node.h
index 9b48c4a..ed736fa 100644
--- a/include/yaml-cpp/value/detail/node.h
+++ b/include/yaml-cpp/value/detail/node.h
@@ -18,34 +18,28 @@ namespace YAML
 		class node
 		{
 		public:
-			node();
+			node(): m_pData(new node_data) {}
+
+			ValueType::value type() const { return m_pData->type(); }
 			
-			ValueType::value type() const;
-			void assign_data(const node& rhs);
-			void set_scalar(const std::string& data);
+			void set_data(const node& rhs) { m_pData = rhs.m_pData; }
+				
+			void set_type(ValueType::value type) { m_pData->set_type(type); }
+			void set_null() { m_pData->set_null(); }
+			void set_scalar(const std::string& scalar) { m_pData->set_scalar(scalar); }
 			
+			// indexing
+			template<typename Key> shared_node operator[](const Key& key) const { return (static_cast<const node_data&>(*m_pData))[key]; }
+			template<typename Key> shared_node operator[](const Key& key) { return (*m_pData)[key]; }
+			template<typename Key> bool remove(const Key& key) { return m_pData->remove(key); }
+			
+			shared_node operator[](shared_node pKey) const { return (static_cast<const node_data&>(*m_pData))[pKey]; }
+			shared_node operator[](shared_node pKey) { return (*m_pData)[pKey]; }
+			bool remove(shared_node pKey) { return m_pData->remove(pKey); }
+
 		private:
 			shared_node_data m_pData;
 		};
-		
-		inline node::node()
-		{
-		}
-		
-		inline ValueType::value node::type() const
-		{
-			return m_pData ? m_pData->type() : ValueType::Null;
-		}
-		
-		inline void node::assign_data(const node& rhs)
-		{
-			m_pData = rhs.m_pData;
-		}
-
-		inline void node::set_scalar(const std::string& data)
-		{
-			m_pData.reset(new node_data(data));
-		}
 	}
 }
 
diff --git a/include/yaml-cpp/value/detail/node_data.h b/include/yaml-cpp/value/detail/node_data.h
index b9395b7..61c7907 100644
--- a/include/yaml-cpp/value/detail/node_data.h
+++ b/include/yaml-cpp/value/detail/node_data.h
@@ -9,7 +9,8 @@
 #include "yaml-cpp/dll.h"
 #include "yaml-cpp/value/type.h"
 #include "yaml-cpp/value/ptr.h"
-#include <pair>
+#include <list>
+#include <utility>
 #include <vector>
 
 namespace YAML
@@ -19,12 +20,29 @@ namespace YAML
 		class node_data
 		{
 		public:
-			explicit node_data(const std::string& scalar);
+			node_data();
 			
-			ValueType::value type() const { return m_type; }
-			const std::string scalar() const { return m_data; }
+			void set_type(ValueType::value type);
+			void set_null();
+			void set_scalar(const std::string& scalar);
+			
+			ValueType::value type() const { return m_isDefined ? m_type : ValueType::Undefined; }
+			const std::string scalar() const { return m_scalar; }
+			
+			// indexing
+			template<typename Key> shared_node operator[](const Key& key) const;
+			template<typename Key> shared_node operator[](const Key& key);
+			template<typename Key> bool remove(const Key& key);
+			
+			shared_node operator[](shared_node pKey) const;
+			shared_node operator[](shared_node pKey);
+			bool remove(shared_node pKey);
 			
 		private:
+			void convert_sequence_to_map();
+
+		private:
+			bool m_isDefined;
 			ValueType::value m_type;
 			
 			// scalar
@@ -36,7 +54,7 @@ namespace YAML
 			
 			// map
 			typedef std::pair<shared_node, shared_node> kv_pair;
-			typedef std::vector<kv_pair> node_map;
+			typedef std::list<kv_pair> node_map;
 			node_map m_map;
 		};
 	}
diff --git a/include/yaml-cpp/value/impl.h b/include/yaml-cpp/value/impl.h
index ddcf1a6..8527c69 100644
--- a/include/yaml-cpp/value/impl.h
+++ b/include/yaml-cpp/value/impl.h
@@ -12,28 +12,37 @@
 
 namespace YAML
 {
-	inline Value::Value(): m_pMemory(new detail::memory_holder)
+	inline Value::Value(): m_pMemory(new detail::memory_holder), m_pNode(m_pMemory->create_node())
 	{
-		EnsureNodeExists();
+		m_pNode->set_null();
+	}
+	
+	inline Value::Value(ValueType::value type): m_pMemory(new detail::memory_holder), m_pNode(m_pMemory->create_node())
+	{
+		m_pNode->set_type(type);
 	}
 	
 	template<typename T>
-	inline Value::Value(const T& rhs): m_pMemory(new detail::memory_holder)
+	inline Value::Value(const T& rhs): m_pMemory(new detail::memory_holder), m_pNode(m_pMemory->create_node())
 	{
 		Assign(rhs);
 	}
 	
-	inline Value::Value(const Value& rhs): m_pNode(rhs.m_pNode), m_pMemory(rhs.m_pMemory)
+	inline Value::Value(const Value& rhs): m_pMemory(rhs.m_pMemory), m_pNode(rhs.m_pNode)
 	{
 	}
 	
+	inline Value::Value(detail::shared_node pNode, detail::shared_memory_holder pMemory): m_pMemory(pMemory), m_pNode(pNode)
+	{
+	}
+
 	inline Value::~Value()
 	{
 	}
 
 	inline ValueType::value Value::Type() const
 	{
-		return m_pNode ? m_pNode->type() : ValueType::Undefined;
+		return m_pNode->type();
 	}
 	
 	// access
@@ -63,19 +72,16 @@ namespace YAML
 	template<>
 	inline void Value::Assign(const std::string& rhs)
 	{
-		EnsureNodeExists();
 		m_pNode->set_scalar(rhs);
 	}
 
 	inline void Value::Assign(const char *rhs)
 	{
-		EnsureNodeExists();
 		m_pNode->set_scalar(rhs);
 	}
 
 	inline void Value::Assign(char *rhs)
 	{
-		EnsureNodeExists();
 		m_pNode->set_scalar(rhs);
 	}
 	
@@ -86,20 +92,10 @@ namespace YAML
 		AssignNode(rhs);
 		return *this;
 	}
-	
-	void Value::EnsureNodeExists()
-	{
-		if(!m_pNode)
-			m_pNode = m_pMemory->create_node();
-	}
-	
+
 	void Value::AssignData(const Value& rhs)
 	{
-		EnsureNodeExists();
-		if(!rhs.m_pNode)
-			throw std::runtime_error("Tried to assign an undefined value");
-		
-		m_pNode->assign_data(*rhs.m_pNode);
+		m_pNode->set_data(*rhs.m_pNode);
 		m_pMemory->merge(*rhs.m_pMemory);
 	}
 
@@ -139,64 +135,68 @@ namespace YAML
 	template<typename Key>
 	inline const Value Value::operator[](const Key& key) const
 	{
-		return Value();
+		detail::shared_node pValue = (static_cast<const detail::node&>(*m_pNode))[key];
+		return Value(pValue, m_pMemory);
 	}
 	
 	template<typename Key>
 	inline Value Value::operator[](const Key& key)
 	{
-		return Value();
+		detail::shared_node pValue = (*m_pNode)[key];
+		return Value(pValue, m_pMemory);
 	}
 	
 	template<typename Key>
 	inline bool Value::remove(const Key& key)
 	{
-		return false;
+		return m_pNode->remove(key);
 	}
 	
 	inline const Value Value::operator[](const Value& key) const
 	{
-		return Value();
+		detail::shared_node pValue = (static_cast<const detail::node&>(*m_pNode))[*key.m_pNode];
+		return Value(pValue, m_pMemory);
 	}
 	
 	inline Value Value::operator[](const Value& key)
 	{
-		return Value();
+		detail::shared_node pValue = (*m_pNode)[*key.m_pNode];
+		return Value(pValue, m_pMemory);
 	}
 	
 	inline bool Value::remove(const Value& key)
 	{
-		return false;
+		return m_pNode->remove(*key.m_pNode);
 	}
 	
 	inline const Value Value::operator[](const char *key) const
 	{
-		return Value();
+		return operator[](std::string(key));
 	}
 	
 	inline Value Value::operator[](const char *key)
 	{
-		return Value();
+		return operator[](std::string(key));
 	}
 	
 	inline bool Value::remove(const char *key)
 	{
-		return false;
+		return m_pNode->remove(std::string(key));
 	}
 	
 	inline const Value Value::operator[](char *key) const
 	{
-		return Value();
+		return operator[](static_cast<const char *>(key));
 	}
 	
 	inline Value Value::operator[](char *key)
 	{
-		return Value();
+		return operator[](static_cast<const char *>(key));
 	}
 	
 	inline bool Value::remove(char *key)
 	{
-		return false;
+		return remove(static_cast<const char *>(key));
 	}
 
 	// free functions
diff --git a/include/yaml-cpp/value/value.h b/include/yaml-cpp/value/value.h
index e1ae370..e9bbee9 100644
--- a/include/yaml-cpp/value/value.h
+++ b/include/yaml-cpp/value/value.h
@@ -59,17 +59,18 @@ namespace YAML
 		bool remove(char *key);
 		
 	private:
+		explicit Value(detail::shared_node pNode, detail::shared_memory_holder pMemory);
+		
 		template<typename T> void Assign(const T& rhs);
 		void Assign(const char *rhs);
 		void Assign(char *rhs);
 
-		void EnsureNodeExists();
 		void AssignData(const Value& rhs);
 		void AssignNode(const Value& rhs);
 		
 	private:
-		detail::shared_node m_pNode;
 		detail::shared_memory_holder m_pMemory;
+		detail::shared_node m_pNode;
 	};
 	
 	int compare(const Value& lhs, const Value& rhs);
diff --git a/src/value/detail/node_data.cpp b/src/value/detail/node_data.cpp
index dc79a75..11ed462 100644
--- a/src/value/detail/node_data.cpp
+++ b/src/value/detail/node_data.cpp
@@ -1,11 +1,132 @@
 #include "yaml-cpp/value/detail/node_data.h"
+#include "yaml-cpp/value/detail/node.h"
+#include <sstream>
 
 namespace YAML
 {
 	namespace detail
 	{
-		node_data::node_data(const std::string& scalar): m_type(ValueType::Scalar), m_scalar(scalar)
+		node_data::node_data(): m_isDefined(false), m_type(ValueType::Null)
 		{
 		}
+
+		void node_data::set_type(ValueType::value type)
+		{
+			if(type == ValueType::Undefined) {
+				m_type = type;
+				m_isDefined = false;
+				return;
+			}
+			
+
+			m_isDefined = true;
+			if(type == m_type)
+				return;
+			
+			m_type = type;
+			
+			switch(m_type) {
+				case ValueType::Null:
+					break;
+				case ValueType::Scalar:
+					m_scalar.clear();
+					break;
+				case ValueType::Sequence:
+					m_sequence.clear();
+					break;
+				case ValueType::Map:
+					m_map.clear();
+					break;
+				case ValueType::Undefined:
+					assert(false);
+					break;
+			}
+		}
+
+		void node_data::set_null()
+		{
+			m_isDefined = true;
+			m_type = ValueType::Null;
+		}
+		
+		void node_data::set_scalar(const std::string& scalar)
+		{
+			m_isDefined = true;
+			m_type = ValueType::Scalar;
+			m_scalar = scalar;
+		}
+
+		// indexing
+		shared_node node_data::operator[](shared_node pKey) const
+		{
+			if(m_type != ValueType::Map)
+				return shared_node(new node);
+			
+			for(node_map::const_iterator it=m_map.begin();it!=m_map.end();++it) {
+				if(it->first == pKey)
+					return it->second;
+			}
+			
+			return shared_node(new node);
+		}
+		
+		shared_node node_data::operator[](shared_node pKey)
+		{
+			switch(m_type) {
+				case ValueType::Undefined:
+				case ValueType::Null:
+				case ValueType::Scalar:
+					m_type = ValueType::Map;
+					m_map.clear();
+					break;
+				case ValueType::Sequence:
+					convert_sequence_to_map();
+					break;
+				case ValueType::Map:
+					break;
+			}
+
+			for(node_map::const_iterator it=m_map.begin();it!=m_map.end();++it) {
+				if(it->first == pKey)
+					return it->second;
+			}
+			
+			shared_node pValue(new node);
+			m_map.push_back(kv_pair(pKey, pValue));
+			return pValue;
+		}
+		
+		bool node_data::remove(shared_node pKey)
+		{
+			if(m_type != ValueType::Map)
+				return false;
+
+			for(node_map::iterator it=m_map.begin();it!=m_map.end();++it) {
+				if(it->first == pKey) {
+					m_map.erase(it);
+					return true;
+				}
+			}
+			
+			return false;
+		}
+
+		void node_data::convert_sequence_to_map()
+		{
+			assert(m_type == ValueType::Sequence);
+			
+			m_map.clear();
+			for(std::size_t i=0;i<m_sequence.size();i++) {
+				std::stringstream stream;
+				stream << i;
+
+				shared_node pKey(new node);
+				pKey->set_scalar(stream.str());
+				m_map.push_back(kv_pair(pKey, m_sequence[i]));
+			}
+			
+			m_sequence.clear();
+			m_type = ValueType::Map;
+		}
 	}
 }