diff --git a/Ahuacatl/ahuacatl-ast-node.c b/Ahuacatl/ahuacatl-ast-node.c
index cf141e0c2a..87c79ff6d7 100644
--- a/Ahuacatl/ahuacatl-ast-node.c
+++ b/Ahuacatl/ahuacatl-ast-node.c
@@ -30,6 +30,7 @@
 #include "Ahuacatl/ahuacatl-functions.h"
 #include "Ahuacatl/ahuacatl-parser-functions.h"
 #include "Ahuacatl/ahuacatl-scope.h"
+#include "Ahuacatl/ahuacatl-variable.h"
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                                    private macros
@@ -233,7 +234,7 @@ TRI_aql_node_t* TRI_CreateNodeForAql (TRI_aql_context_t* const context,
   }
   
   {
-    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name);
+    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name, node);
     ADD_MEMBER(variable)
     ADD_MEMBER(expression)
   }
@@ -260,7 +261,7 @@ TRI_aql_node_t* TRI_CreateNodeLetAql (TRI_aql_context_t* const context,
   }
   
   {
-    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name);
+    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name, node);
     ADD_MEMBER(variable)
     ADD_MEMBER(expression)
   }
@@ -305,7 +306,7 @@ TRI_aql_node_t* TRI_CreateNodeCollectAql (TRI_aql_context_t* const context,
 
   ADD_MEMBER(list)
   if (name) {
-    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name);
+    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name, node);
     ADD_MEMBER(variable)
   }
 
@@ -365,7 +366,7 @@ TRI_aql_node_t* TRI_CreateNodeAssignAql (TRI_aql_context_t* const context,
   CREATE_NODE(AQL_NODE_ASSIGN)
  
   {
-    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name);
+    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, name, node);
     ADD_MEMBER(variable)
     ADD_MEMBER(expression)
   }
@@ -378,14 +379,15 @@ TRI_aql_node_t* TRI_CreateNodeAssignAql (TRI_aql_context_t* const context,
 ////////////////////////////////////////////////////////////////////////////////
 
 TRI_aql_node_t* TRI_CreateNodeVariableAql (TRI_aql_context_t* const context,
-                                           const char* const name) {
+                                           const char* const name,
+                                           TRI_aql_node_t* const definingNode) {
   CREATE_NODE(AQL_NODE_VARIABLE)
    
   if (!name) {
     ABORT_OOM
   }
   
-  if (!TRI_AddVariableScopeAql(context, name)) {
+  if (!TRI_AddVariableScopeAql(context, name, definingNode)) {
     // duplicate variable name 
     TRI_SetErrorContextAql(context, TRI_ERROR_QUERY_VARIABLE_REDECLARED, name); 
     return NULL;
@@ -412,9 +414,12 @@ TRI_aql_node_t* TRI_CreateNodeCollectionAql (TRI_aql_context_t* const context,
     TRI_SetErrorContextAql(context, TRI_ERROR_QUERY_COLLECTION_NOT_FOUND, name);
     return NULL;
   }
-  
-  TRI_AQL_NODE_STRING(node) = (char*) name;
 
+  {
+    TRI_aql_node_t* nameNode = TRI_CreateNodeValueStringAql(context, name);
+    ADD_MEMBER(nameNode)
+  }
+  
   if (!TRI_AddCollectionAql(context, name)) {
     return NULL;
   }
@@ -752,7 +757,7 @@ TRI_aql_node_t* TRI_CreateNodeSubqueryAql (TRI_aql_context_t* const context,
      
   {
     // add the temporary variable
-    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, TRI_GetNameParseAql(context));
+    TRI_aql_node_t* variable = TRI_CreateNodeVariableAql(context, TRI_GetNameParseAql(context), node);
     ADD_MEMBER(variable)
   }
  
@@ -811,8 +816,9 @@ TRI_aql_node_t* TRI_CreateNodeExpandAql (TRI_aql_context_t* const context,
   }
 
   {
-    TRI_aql_node_t* variable1 = TRI_CreateNodeVariableAql(context, varname);
-    TRI_aql_node_t* variable2 = TRI_CreateNodeVariableAql(context, TRI_GetNameParseAql(context));
+    // TODO: check if 3rd parameters' values are correct for these
+    TRI_aql_node_t* variable1 = TRI_CreateNodeVariableAql(context, varname, node);
+    TRI_aql_node_t* variable2 = TRI_CreateNodeVariableAql(context, TRI_GetNameParseAql(context), node);
 
     ADD_MEMBER(variable1)
     ADD_MEMBER(variable2)
diff --git a/Ahuacatl/ahuacatl-ast-node.h b/Ahuacatl/ahuacatl-ast-node.h
index 053987ba12..0f9cbc065e 100644
--- a/Ahuacatl/ahuacatl-ast-node.h
+++ b/Ahuacatl/ahuacatl-ast-node.h
@@ -337,7 +337,8 @@ TRI_aql_node_t* TRI_CreateNodeParameterAql (TRI_aql_context_t* const,
 ////////////////////////////////////////////////////////////////////////////////
 
 TRI_aql_node_t* TRI_CreateNodeVariableAql (TRI_aql_context_t* const,
-                                           const char* const);
+                                           const char* const,
+                                           TRI_aql_node_t* const);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief create an AST collection node
diff --git a/Ahuacatl/ahuacatl-codegen.c b/Ahuacatl/ahuacatl-codegen.c
index 08b94cd505..b841940198 100644
--- a/Ahuacatl/ahuacatl-codegen.c
+++ b/Ahuacatl/ahuacatl-codegen.c
@@ -1168,7 +1168,9 @@ static void ProcessArgList (TRI_aql_codegen_js_t* const generator,
 
     if (parameter->_type == AQL_NODE_COLLECTION && TRI_ConvertParameterFunctionAql(function, i)) {
       // collection arguments will be created as string argument => e.g. "users"
-      ScopeOutputQuoted(generator, TRI_AQL_NODE_STRING(parameter));
+      TRI_aql_node_t* nameNode = TRI_AQL_NODE_MEMBER(parameter, 0);
+
+      ScopeOutputQuoted(generator, TRI_AQL_NODE_STRING(nameNode));
     }
     else {
       // anything else will be created as is
@@ -1226,9 +1228,9 @@ static void ProcessIndexed (TRI_aql_codegen_js_t* const generator,
 
 static void ProcessCollection (TRI_aql_codegen_js_t* const generator,
                                const TRI_aql_node_t* const node) {
-  ScopeOutput(generator, "AHUACATL_GET_DOCUMENTS('");
-  ScopeOutput(generator, TRI_AQL_NODE_STRING(node));
-  ScopeOutput(generator, "')");
+  ScopeOutput(generator, "AHUACATL_GET_DOCUMENTS(");
+  ProcessNode(generator, TRI_AQL_NODE_MEMBER(node, 0));
+  ScopeOutput(generator, ")");
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1253,7 +1255,7 @@ static void ProcessHintedCollection (TRI_aql_codegen_js_t* const generator,
   variableName = TRI_AQL_NODE_STRING(nameNode);
   assert(variableName);
 
-  collectionName = TRI_AQL_NODE_STRING(collectionNode);
+  collectionName = TRI_AQL_NODE_STRING((TRI_AQL_NODE_MEMBER(collectionNode, 0)));
   assert(collectionName);
 
   collection = TRI_GetCollectionAql(generator->_context, collectionName);
diff --git a/Ahuacatl/ahuacatl-context.c b/Ahuacatl/ahuacatl-context.c
index d3e425ff73..d3a0aeac9f 100644
--- a/Ahuacatl/ahuacatl-context.c
+++ b/Ahuacatl/ahuacatl-context.c
@@ -34,6 +34,7 @@
 #include "Ahuacatl/ahuacatl-parser-functions.h"
 #include "Ahuacatl/ahuacatl-scope.h"
 #include "Ahuacatl/ahuacatl-tree-dump.h"
+#include "Ahuacatl/ahuacatl-variable.h"
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                                    private macros
diff --git a/Ahuacatl/ahuacatl-context.h b/Ahuacatl/ahuacatl-context.h
index 551fec298b..a856994f94 100644
--- a/Ahuacatl/ahuacatl-context.h
+++ b/Ahuacatl/ahuacatl-context.h
@@ -40,7 +40,6 @@
 
 #include "Ahuacatl/ahuacatl-error.h"
 #include "Ahuacatl/ahuacatl-parser.h"
-#include "Ahuacatl/ahuacatl-variable.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/Ahuacatl/ahuacatl-optimiser.c b/Ahuacatl/ahuacatl-optimiser.c
index a14bb56b4a..a55bfb1d17 100644
--- a/Ahuacatl/ahuacatl-optimiser.c
+++ b/Ahuacatl/ahuacatl-optimiser.c
@@ -538,6 +538,18 @@ TRY_LOOP:
   return node;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief optimise a reference expression
+////////////////////////////////////////////////////////////////////////////////
+
+static TRI_aql_node_t* OptimiseReference (TRI_aql_context_t* const context,
+                                          TRI_aql_node_t* node) {
+  // TODO: find variable in current symbol table
+  // follow references until variable declaration is found
+  // if variable value at source is constant, copy the constant into here as well
+  return node;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief optimise an arithmetic operation with one operand
 ////////////////////////////////////////////////////////////////////////////////
@@ -915,6 +927,8 @@ static TRI_aql_node_t* OptimiseNode (TRI_aql_context_t* const context,
       return OptimiseFilter(context, node);
     case AQL_NODE_FCALL:
       return OptimiseFcall(context, node);
+    case AQL_NODE_REFERENCE:
+      return OptimiseReference(context, node);
     default: 
       break;
   }
diff --git a/Ahuacatl/ahuacatl-scope.c b/Ahuacatl/ahuacatl-scope.c
index 618979ad27..d04e3681c0 100644
--- a/Ahuacatl/ahuacatl-scope.c
+++ b/Ahuacatl/ahuacatl-scope.c
@@ -26,6 +26,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Ahuacatl/ahuacatl-scope.h" 
+#include "Ahuacatl/ahuacatl-variable.h"
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                                 private functions
@@ -314,7 +315,9 @@ bool TRI_VariableExistsScopeAql (TRI_aql_context_t* const context,
 /// @brief push a variable into the current scope's symbol table
 ////////////////////////////////////////////////////////////////////////////////
 
-bool TRI_AddVariableScopeAql (TRI_aql_context_t* const context, const char* name) {
+bool TRI_AddVariableScopeAql (TRI_aql_context_t* const context, 
+                              const char* name, 
+                              TRI_aql_node_t* const definingNode) {
   TRI_aql_variable_t* variable;
   TRI_aql_scope_t* scope;
   
@@ -325,7 +328,7 @@ bool TRI_AddVariableScopeAql (TRI_aql_context_t* const context, const char* name
     return false;
   }
 
-  variable = TRI_CreateVariableAql(name);
+  variable = TRI_CreateVariableAql(name, definingNode);
   if (variable == NULL) {
     return false;
   }
diff --git a/Ahuacatl/ahuacatl-scope.h b/Ahuacatl/ahuacatl-scope.h
index 87adc0bbb4..5277220693 100644
--- a/Ahuacatl/ahuacatl-scope.h
+++ b/Ahuacatl/ahuacatl-scope.h
@@ -30,6 +30,7 @@
 
 #include <BasicsC/associative.h>
 
+#include "Ahuacatl/ahuacatl-ast-node.h"
 #include "Ahuacatl/ahuacatl-context.h"
 #include "Ahuacatl/ahuacatl-log.h"
 
@@ -123,7 +124,9 @@ bool TRI_VariableExistsScopeAql (TRI_aql_context_t* const, const char* const);
 /// @brief push a variable into the current scope's symbol table
 ////////////////////////////////////////////////////////////////////////////////
 
-bool TRI_AddVariableScopeAql (TRI_aql_context_t* const, const char*);
+bool TRI_AddVariableScopeAql (TRI_aql_context_t* const, 
+                              const char*, 
+                              TRI_aql_node_t* const);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @}
diff --git a/Ahuacatl/ahuacatl-tree-dump.c b/Ahuacatl/ahuacatl-tree-dump.c
index 75b1f2179c..4fb4e8df09 100644
--- a/Ahuacatl/ahuacatl-tree-dump.c
+++ b/Ahuacatl/ahuacatl-tree-dump.c
@@ -138,7 +138,6 @@ static void DumpNode (void* data, const TRI_aql_node_t* const node) {
 
     case AQL_NODE_VARIABLE:
     case AQL_NODE_ATTRIBUTE:
-    case AQL_NODE_COLLECTION:
     case AQL_NODE_REFERENCE:
     case AQL_NODE_PARAMETER:
     case AQL_NODE_ARRAY_ELEMENT:
diff --git a/Ahuacatl/ahuacatl-variable.c b/Ahuacatl/ahuacatl-variable.c
index 22533be717..e1396b391a 100644
--- a/Ahuacatl/ahuacatl-variable.c
+++ b/Ahuacatl/ahuacatl-variable.c
@@ -40,7 +40,8 @@
 /// @brief register a new variable
 ////////////////////////////////////////////////////////////////////////////////
 
-TRI_aql_variable_t* TRI_CreateVariableAql (const char* const name) { 
+TRI_aql_variable_t* TRI_CreateVariableAql (const char* const name,
+                                           TRI_aql_node_t* const definingNode) { 
   TRI_aql_variable_t* variable;
 
   variable = (TRI_aql_variable_t*) TRI_Allocate(TRI_UNKNOWN_MEM_ZONE, sizeof(TRI_aql_variable_t), false);
@@ -57,6 +58,9 @@ TRI_aql_variable_t* TRI_CreateVariableAql (const char* const name) {
   }
 
   variable->_refCount = 0;
+  variable->_definingNode = definingNode;
+
+  assert(definingNode);
 
   return variable;
 }
diff --git a/Ahuacatl/ahuacatl-variable.h b/Ahuacatl/ahuacatl-variable.h
index d04354e586..e5be1b77a5 100644
--- a/Ahuacatl/ahuacatl-variable.h
+++ b/Ahuacatl/ahuacatl-variable.h
@@ -34,6 +34,8 @@
 #include <BasicsC/vector.h>
 #include <BasicsC/associative.h>
 
+#include "Ahuacatl/ahuacatl-ast-node.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -54,6 +56,7 @@ extern "C" {
 typedef struct TRI_aql_variable_s {
   char* _name;
   uint32_t _refCount;
+  TRI_aql_node_t* _definingNode;
 }
 TRI_aql_variable_t;
 
@@ -74,7 +77,8 @@ TRI_aql_variable_t;
 /// @brief register a new variable
 ////////////////////////////////////////////////////////////////////////////////
 
-TRI_aql_variable_t* TRI_CreateVariableAql (const char* const);
+TRI_aql_variable_t* TRI_CreateVariableAql (const char* const,
+                                           TRI_aql_node_t* const);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief free an existing variable