diff --git a/Svelto.ECS/EGIDMapper.cs b/Svelto.ECS/EGIDMapper.cs
index cec4ee9..f9057fd 100644
--- a/Svelto.ECS/EGIDMapper.cs
+++ b/Svelto.ECS/EGIDMapper.cs
@@ -6,9 +6,11 @@ namespace Svelto.ECS
     {
         internal TypeSafeDictionary<T> map;
 
-        public uint this[EGID index]
+        public T[] entities(EGID id, out uint index)
         {
-            get { return map.FindElementIndex(index.entityID); }
+                int count;
+                index = map.FindElementIndex(id.entityID); 
+                return map.GetFasterValuesBuffer(out count);
         }
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/EntitiesDB.cs b/Svelto.ECS/EntitiesDB.cs
index c584eaf..175e84a 100644
--- a/Svelto.ECS/EntitiesDB.cs
+++ b/Svelto.ECS/EntitiesDB.cs
@@ -42,17 +42,25 @@ namespace Svelto.ECS.Internal
             return typeSafeDictionary.GetFasterValuesBuffer(out count);
         }
         
-        public T[] QueryEntities<T>(int groupID, ref EGIDMapper<T> mapper) where T : IEntityStruct
+        public EGIDMapper<T> QueryMappedEntities<T>() where T : IEntityStruct
+        {
+            return QueryMappedEntities<T>(ExclusiveGroup.StandardEntitiesGroup);
+        }
+        
+        public EGIDMapper<T> QueryMappedEntities<T>(int groupID) where T : IEntityStruct
         {
             TypeSafeDictionary<T> typeSafeDictionary;
             
             if (QueryEntitySafeDictionary(groupID, out typeSafeDictionary) == false) 
                 throw new EntitiesDBException("Entity group not found type: ".FastConcat(typeof(T)).FastConcat(" groupID: ").FastConcat(groupID));
-            
+
+            EGIDMapper<T> mapper;
             mapper.map = typeSafeDictionary;
 
             int count;
-            return typeSafeDictionary.GetFasterValuesBuffer(out count);
+            typeSafeDictionary.GetFasterValuesBuffer(out count);
+
+            return mapper;
         }
 
         public T[] QueryEntitiesAndIndex<T>(EGID entityGID, out uint index) where T : IEntityStruct
@@ -130,11 +138,22 @@ namespace Svelto.ECS.Internal
 
         public void ExecuteOnEntities<T>(int groupID, ActionRef<T> action) where T : IEntityStruct
         {
-            int count;
-            var entities = QueryEntities<T>(groupID, out count);
-
-            for (int i = 0; i < count; i++)
+            int                   count;
+            TypeSafeDictionary<T> typeSafeDictionary;
+            if (QueryEntitySafeDictionary(@groupID, out typeSafeDictionary) == false) return;
+            
+            var entities = typeSafeDictionary.GetFasterValuesBuffer(out count);
+            
+            for (var i = 0; i < count; i++)
                 action(ref entities[i]);
+            
+            SafetyChecks(typeSafeDictionary, count);
+        }
+
+        static void SafetyChecks<T>(TypeSafeDictionary<T> typeSafeDictionary, int count) where T : IEntityStruct
+        {
+            if (typeSafeDictionary.Count != count)
+                throw new EntitiesDBException("Entities cannot be swapped or removed during an iteration");
         }
 
         public void ExecuteOnEntities<T>(ActionRef<T> action) where T : IEntityStruct
@@ -144,17 +163,27 @@ namespace Svelto.ECS.Internal
 
         public void ExecuteOnEntities<T, W>(int groupID, ref W value, ActionRef<T, W> action) where T : IEntityStruct
         {
-            int count;
-            var entities = QueryEntities<T>(groupID, out count);
-
-            for (int i = 0; i < count; i++)
+            int                   count;
+            TypeSafeDictionary<T> typeSafeDictionary;
+            if (QueryEntitySafeDictionary(@groupID, out typeSafeDictionary) == false) return;
+            
+            var entities = typeSafeDictionary.GetFasterValuesBuffer(out count);
+            
+            for (var i = 0; i < count; i++)
                 action(ref entities[i], ref value);
+            
+            SafetyChecks(typeSafeDictionary, count);
         }
 
         public void ExecuteOnEntities<T, W>(ref W value, ActionRef<T, W> action) where T : IEntityStruct
         {
             ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
         }
+        
+        public void ExecuteOnEntities<T, T1, W>(W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct
+        {
+            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
+        }
 
         public void ExecuteOnAllEntities<T>(ActionRef<T> action) where T : IEntityStruct
         {
@@ -167,11 +196,15 @@ namespace Svelto.ECS.Internal
                 for (int j = 0; j < count; j++)
                 {
                     int innerCount;
-                    var safedic  = typeSafeDictionaries[j];
-                    var casted   = safedic as TypeSafeDictionary<T>;
+                    var typeSafeDictionary = typeSafeDictionaries[j];
+                    var casted             = typeSafeDictionary as TypeSafeDictionary<T>;
+                    
                     var entities = casted.GetFasterValuesBuffer(out innerCount);
+
                     for (int i = 0; i < innerCount; i++)
                         action(ref entities[i]);
+                    
+                    SafetyChecks(casted, count);
                 }
             }
         }
@@ -187,11 +220,15 @@ namespace Svelto.ECS.Internal
                 for (int j = 0; j < count; j++)
                 {
                     int innerCount;
-                    var safedic  = typeSafeDictionaries[j];
-                    var casted   = safedic as TypeSafeDictionary<T>;
+                    var typeSafeDictionary = typeSafeDictionaries[j];
+                    var casted   = typeSafeDictionary as TypeSafeDictionary<T>;
+                    
                     var entities = casted.GetFasterValuesBuffer(out innerCount);
+
                     for (int i = 0; i < innerCount; i++)
                         action(ref entities[i], ref value);
+                    
+                    SafetyChecks(casted, count);
                 }
             }
         }
@@ -203,20 +240,46 @@ namespace Svelto.ECS.Internal
             if (QueryEntitySafeDictionary(@group, out typeSafeDictionary) == false) return;
             
             var entities  = typeSafeDictionary.GetFasterValuesBuffer(out count);
+
+            EGIDMapper<T1> map = QueryMappedEntities<T1>(group);
+            
+            for (var i = 0; i < count; i++)
+            {
+                uint index;
+                action(ref entities[i], ref map.entities(entities[i].ID, out index)[index]);
+            }
+
+            SafetyChecks(typeSafeDictionary, count);
+        }
+        
+        public void ExecuteOnEntities<T, T1, W>(int group, ref W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct
+        {
+            int                   count;
+            TypeSafeDictionary<T> typeSafeDictionary;
+            if (QueryEntitySafeDictionary(@group, out typeSafeDictionary) == false) return;
+            
+            var entities = typeSafeDictionary.GetFasterValuesBuffer(out count);
+
+            EGIDMapper<T1> map = QueryMappedEntities<T1>(group);
             
             for (var i = 0; i < count; i++)
             {
                 uint index;
-                action(ref entities[i], ref QueryEntitiesAndIndex<T1>(entities[i].ID, out index)[index]);
-                if (typeSafeDictionary.Count != count)
-                    throw new EntitiesDBException("Entities cannot be swapped or removed during an iteration");
+                action(ref entities[i], ref map.entities(entities[i].ID, out index)[index], ref value);
             }
+
+            SafetyChecks(typeSafeDictionary, count);
         }
 
         public void ExecuteOnEntities<T, T1>(ActionRef<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct
         {
             ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, action);
         }
+        
+        public void ExecuteOnEntities<T, T1, W>(ref W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct
+        {
+            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
+        }
 
         public bool Exists<T>(EGID entityGID) where T : IEntityStruct
         {
diff --git a/Svelto.ECS/IEntitiesDB.cs b/Svelto.ECS/IEntitiesDB.cs
index 7289d0c..a8f7940 100644
--- a/Svelto.ECS/IEntitiesDB.cs
+++ b/Svelto.ECS/IEntitiesDB.cs
@@ -1,4 +1,3 @@
-using System;
 using Svelto.DataStructures;
 using Svelto.Utilities;
 
@@ -30,41 +29,95 @@ namespace Svelto.ECS
         /// over EntityView
         /// </summary>
         T QueryEntityView<T>(EGID egid) where T : class, IEntityStruct;
-
-        //to use with EntityViews, EntityStructs and EntityViewStructs
+        /// <summary>
+        /// Fast and raw (therefore not safe) return of entities buffer
+        /// Modifying a buffer would compromise the integrity of the whole DB
+        /// so they are meant to be used only in performance critical path
+        /// </summary>
+        /// <param name="count"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <returns></returns>
         T[] QueryEntities<T>(out int count) where T : IEntityStruct;
-        T[] QueryEntities<T>(int group, out int count) where T : IEntityStruct;
-        T[] QueryEntities<T>(int groupID, ref EGIDMapper<T> mapper) where T : IEntityStruct;
-        
-        T[] QueryEntitiesAndIndex<T>(EGID entityGid, out uint index) where T : IEntityStruct;
-        bool TryQueryEntitiesAndIndex<T>(EGID entityGid, out uint index, out T[] array) where T : IEntityStruct;
-
-        //to use with EntityViews, EntityStructs and EntityViewStructs
-        
-        void ExecuteOnEntity<T>(EGID egid, ActionRef<T> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T>(int id, ActionRef<T> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T>(int id, int groupid, ActionRef<T> action) where T : IEntityStruct;
-
+        T[] QueryEntities<T>(int group, out int count) where T : IEntityStruct;       
+        /// <summary>
+        /// this version returns a mapped version of the entity array so that is possible to find the
+        /// index of the entity inside the returned buffer through it's EGID
+        /// However mapping can be slow so it must be used for not performance critical paths
+        /// </summary>
+        /// <param name="groupID"></param>
+        /// <param name="mapper"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <returns></returns>
+        EGIDMapper<T> QueryMappedEntities<T>(int groupID) where T : IEntityStruct;
+        EGIDMapper<T> QueryMappedEntities<T>() where T : IEntityStruct;
+        /// <summary>
+        /// Execute an action on entities. Be sure that the action is not capturing variables
+        /// otherwise you will allocate memory which will have a great impact on the execution performance.
+        /// ExecuteOnEntities can be used to iterate safely over entities, several checks are in place
+        /// to be sure that everything will be done correctly.
+        /// Cache friendliness is guaranteed if only Entity Structs are used, but 
+        /// </summary>
+        /// <param name="egid"></param>
+        /// <param name="action"></param>
+        /// <typeparam name="T"></typeparam>
         void ExecuteOnEntities<T>(int groupID, ActionRef<T> action) where T : IEntityStruct;
         void ExecuteOnEntities<T>(ActionRef<T> action) where T : IEntityStruct;
-
-        void ExecuteOnEntity<T, W>(EGID egid, ref W value, ActionRef<T, W> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T, W>(int id, ref W value, ActionRef<T, W> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T, W>(int id, int groupid, ref W value, ActionRef<T, W> action) where T : IEntityStruct;
-        
         void ExecuteOnEntities<T, W>(int groupID, ref W value, ActionRef<T, W> action) where T : IEntityStruct;
         void ExecuteOnEntities<T, W>(ref W value, ActionRef<T, W> action) where T : IEntityStruct;
-
-        void ExecuteOnAllEntities<T>(ActionRef<T> action) where T : IEntityStruct;
-        void ExecuteOnAllEntities<T, W>(ref W value, ActionRef<T, W> action) where T : IEntityStruct;
-        
+        /// <summary>
+        /// This specialized version allows to execute actions on multiple entity views or entity structs
+        /// Safety checks are in place. This function doesn't guarantee cache
+        /// friendliness even if just EntityStructs are used. 
+        /// </summary>
+        /// <param name="groupID"></param>
+        /// <param name="action"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <typeparam name="T1"></typeparam>
         void ExecuteOnEntities<T, T1>(int groupID, ActionRef<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct;
         void ExecuteOnEntities<T, T1>(ActionRef<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct;
+        
+        void ExecuteOnEntities<T, T1, W>(int groupID, ref W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct;
+        void ExecuteOnEntities<T, T1, W>(ref W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct;
+        void ExecuteOnEntities<T, T1, W>(W value, ActionRef<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct;
+        /// <summary>
+        /// Execute an action on ALL the entities regardless the group. This function doesn't guarantee cache
+        /// friendliness even if just EntityStructs are used. 
+        /// Safety checks are in place 
+        /// </summary>
+        /// <param name="action"></param>
+        /// <typeparam name="T"></typeparam>
+        void ExecuteOnAllEntities<T>(ActionRef<T> action) where T : IEntityStruct;
+        void ExecuteOnAllEntities<T, W>(ref W  value, ActionRef<T, W> action) where T : IEntityStruct;
+        /// <summary>
+        /// ECS is meant to work on a set of Entities. Working on a single entity is sometime necessary, but using
+        /// the following functions inside a loop would be a mistake as performance can be significantly impacted
+        /// return the buffer and the index of the entity inside the buffer using the input EGID 
+        /// </summary>
+        /// <param name="entityGid"></param>
+        /// <param name="index"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <returns></returns>
+        T[] QueryEntitiesAndIndex<T>(EGID entityGid, out uint index) where T : IEntityStruct;
+        bool TryQueryEntitiesAndIndex<T>(EGID entityGid, out uint index, out T[] array) where T : IEntityStruct;
+        /// <summary>
+        /// ECS is meant to work on a set of Entities. Working on a single entity is sometime necessary, but using
+        /// the following functions inside a loop would be a mistake as performance can be significantly impacted
+        /// Execute an action on a specific Entity. Be sure that the action is not capturing variables
+        /// otherwise you will allocate memory which will have a great impact on the execution performance
+        /// </summary>
+        /// <param name="egid"></param>
+        /// <param name="action"></param>
+        /// <typeparam name="T"></typeparam>
+        void ExecuteOnEntity<T>(EGID egid, ActionRef<T> action) where T : IEntityStruct;
+        void ExecuteOnEntity<T>(int     id,   ActionRef<T> action) where T : IEntityStruct;
+        void ExecuteOnEntity<T>(int     id,   int          groupid, ActionRef<T>    action) where T : IEntityStruct;
+        void ExecuteOnEntity<T, W>(EGID egid, ref W        value,   ActionRef<T, W> action) where T : IEntityStruct;
+        void ExecuteOnEntity<T, W>(int  id,   ref W        value,   ActionRef<T, W> action) where T : IEntityStruct;
+        void ExecuteOnEntity<T, W>(int  id,   int          groupid, ref W           value, ActionRef<T, W> action) where T : IEntityStruct;
 
         bool Exists<T>(EGID egid) where T : IEntityStruct;
         
         bool HasAny<T>() where T:IEntityStruct;
         bool HasAny<T>(int group) where T:IEntityStruct;
-        
     }
 }
\ No newline at end of file