diff --git a/.gitmodules b/.gitmodules
index 532d6f0..e69de29 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +0,0 @@
-[submodule "Svelto.Common"]
-	path = Svelto.Common
-	url = https://github.com/sebas77/Svelto.Common.git
diff --git a/README.md b/README.md
index e74f30a..0d3f59b 100644
--- a/README.md
+++ b/README.md
@@ -52,7 +52,8 @@ Note: I included the IoC articles just to show how I shifted over the years from
 
 **Official Chat**
 
-* https://discord.gg/3qAdjDb 
+* https://gitter.im/Svelto-ECS/Lobby
+* https://discord.gg/3qAdjDb (Discord chat is under test, if it will become more popular I will drop gitter support)
 
 **NED-Studio Svelto ECS inspector (WIP)**
 
diff --git a/Svelto.Common b/Svelto.Common
deleted file mode 160000
index 5548758..0000000
--- a/Svelto.Common
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 554875838f1743017981df428243bba80fe3ece1
diff --git a/Svelto.ECS/EGID.cs b/Svelto.ECS/EGID.cs
index e4e5612..857acc9 100644
--- a/Svelto.ECS/EGID.cs
+++ b/Svelto.ECS/EGID.cs
@@ -24,11 +24,11 @@ namespace Svelto.ECS
             _GID = MAKE_GLOBAL_ID(entityID, groupID);
         }
         
-        public EGID(int entityID) : this()
+        public EGID(int entityID, ExclusiveGroup groupID) : this()
         {
-            _GID = MAKE_GLOBAL_ID(entityID, ExclusiveGroup.StandardEntitiesGroup);
+            _GID = MAKE_GLOBAL_ID(entityID, (int) groupID);
         }
-
+        
         static long MAKE_GLOBAL_ID(int entityId, int groupId)
         {
             return (long)groupId << 32 | ((long)(uint)entityId & 0xFFFFFFFF);
diff --git a/Svelto.ECS/EnginesRoot.Engines.cs b/Svelto.ECS/EnginesRoot.Engines.cs
index 45a3085..36fe83d 100644
--- a/Svelto.ECS/EnginesRoot.Engines.cs
+++ b/Svelto.ECS/EnginesRoot.Engines.cs
@@ -40,11 +40,10 @@ namespace Svelto.ECS
             _otherEngines = new FasterList<IEngine>();
 
             _groupEntityDB = new Dictionary<int, Dictionary<Type, ITypeSafeDictionary>>();
-            _groupEntityDB[ExclusiveGroup.StandardEntitiesGroup] = new Dictionary<Type, ITypeSafeDictionary>();
             _groupedGroups = new Dictionary<Type, FasterDictionary<int, ITypeSafeDictionary>>();
             _groupedEntityToAdd = new DoubleBufferedEntitiesToAdd<Dictionary<int, Dictionary<Type, ITypeSafeDictionary>>>();
 
-            _DB = new entitiesDB(_groupEntityDB, _groupedGroups);
+            _DB = new EntitiesDB(_groupEntityDB, _groupedGroups);
 
             _scheduler = entityViewScheduler;
             _scheduler.Schedule(new WeakAction(SubmitEntityViews));
diff --git a/Svelto.ECS/EnginesRoot.Entities.cs b/Svelto.ECS/EnginesRoot.Entities.cs
index 3ba4a9c..381074a 100644
--- a/Svelto.ECS/EnginesRoot.Entities.cs
+++ b/Svelto.ECS/EnginesRoot.Entities.cs
@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using Svelto.DataStructures.Experimental;
 using Svelto.ECS.Internal;
 
@@ -213,7 +214,7 @@ namespace Svelto.ECS
             return new EGID(firstID, toGroupId);
         }
 
-        readonly entitiesDB         _DB;
+        readonly EntitiesDB         _DB;
         
         int                         _newEntitiesBuiltToProcess;
     }
diff --git a/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs b/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
index 1288ce0..9f3739d 100644
--- a/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
+++ b/Svelto.ECS/EnginesRoot.GenericEntityFactory.cs
@@ -1,4 +1,4 @@
-#if ENGINE_PROFILER_ENABLED && UNITY_EDITOR
+#if ENGINE_PROFILER_ENABLED && UNITY_EDITOR
 using Svelto.ECS.Profiler;
 #endif
 
@@ -15,11 +15,6 @@ namespace Svelto.ECS
                 _weakEngine = weakReference;
             }
 
-            public EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T : IEntityDescriptor, new()
-            {
-                return _weakEngine.Target.BuildEntity<T>(new EGID(entityID), implementors);
-            }
-
             public EntityStructInitializer BuildEntity<T>(int entityID, ExclusiveGroup groupID, object[] implementors) where T : IEntityDescriptor, new()
             {
                 return _weakEngine.Target.BuildEntity<T>(new EGID(entityID, (int)groupID), implementors);
@@ -30,11 +25,6 @@ namespace Svelto.ECS
                 return _weakEngine.Target.BuildEntity<T>(egid, implementors);
             }
 
-            public EntityStructInitializer BuildEntity(int entityID, IEntityDescriptor descriptorEntity, object[] implementors)
-            {
-                return _weakEngine.Target.BuildEntity(new EGID(entityID), descriptorEntity, implementors);
-            }
-
             public EntityStructInitializer BuildEntity(EGID egid, IEntityDescriptor descriptorEntity, object[] implementors)
             {
                 return _weakEngine.Target.BuildEntity(egid, descriptorEntity, implementors);
@@ -45,11 +35,6 @@ namespace Svelto.ECS
                 return _weakEngine.Target.BuildEntity(new EGID(entityID, (int)groupID), descriptorEntity, implementors);
             }
             
-            public void PreallocateEntitySpace<T>(int size) where T : IEntityDescriptor, new()
-            {
-                _weakEngine.Target.Preallocate<T>(ExclusiveGroup.StandardEntitiesGroup, size);
-            }
-            
             public void PreallocateEntitySpace<T>(ExclusiveGroup groupID, int size) where T : IEntityDescriptor, new()
             {
                 _weakEngine.Target.Preallocate<T>((int)groupID, size);
diff --git a/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs b/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
index 31b2ba0..f689306 100644
--- a/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
+++ b/Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs
@@ -1,4 +1,4 @@
-using Svelto.ECS.Internal;
+using Svelto.ECS.Internal;
 
 #if ENGINE_PROFILER_ENABLED && UNITY_EDITOR
 using Svelto.ECS.Profiler;
@@ -17,16 +17,16 @@ namespace Svelto.ECS
                 _weakReference = weakReference;
             }
 
-            public void RemoveEntity<T>(int entityID) where T : IEntityDescriptor, new()
-            {
-                _weakReference.Target.MoveEntity<T>(new EGID(entityID));
-            }
-            
             public void RemoveEntity<T>(int entityID, int groupID) where T : IEntityDescriptor, new()
             {
                 _weakReference.Target.MoveEntity<T>(new EGID(entityID, groupID));
             }
 
+            public void RemoveEntity<T>(int entityID, ExclusiveGroup groupID) where T : IEntityDescriptor, new()
+            {
+                _weakReference.Target.MoveEntity<T>(new EGID(entityID, (int) groupID));
+            }
+
             public void RemoveEntity<T>(EGID entityEGID) where T : IEntityDescriptor, new()
             {
                 _weakReference.Target.MoveEntity<T>(entityEGID);
@@ -37,25 +37,40 @@ namespace Svelto.ECS
                 _weakReference.Target.RemoveGroupAndEntitiesFromDB(groupID);
             }
 
+            public void RemoveGroupAndEntities(ExclusiveGroup groupID)
+            {
+                _weakReference.Target.RemoveGroupAndEntitiesFromDB((int) groupID);
+            }
+
             public EGID SwapEntityGroup<T>(int entityID, int fromGroupID, int toGroupID) where T : IEntityDescriptor, new()
             {
                 return _weakReference.Target.SwapEntityGroup<T>(entityID, fromGroupID, toGroupID);
             }
 
-            public EGID SwapEntityGroup<T>(EGID id, int toGroupID = ExclusiveGroup.StandardEntitiesGroup) where T : IEntityDescriptor, new()
+            public EGID SwapEntityGroup<T>(int entityID, ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new()
+            {
+                return _weakReference.Target.SwapEntityGroup<T>(entityID, (int) fromGroupID, (int) toGroupID);
+            }
+
+            public EGID SwapEntityGroup<T>(EGID id, int toGroupID) where T : IEntityDescriptor, new()
             {
                 return _weakReference.Target.SwapEntityGroup<T>(id.entityID, id.groupID, toGroupID);
             }
 
-            public EGID SwapEntityGroup<T>(int entityID, int toGroupID) where T : IEntityDescriptor, new()
+            public EGID SwapEntityGroup<T>(EGID id, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new()
             {
-                return _weakReference.Target.SwapEntityGroup<T>(entityID, ExclusiveGroup.StandardEntitiesGroup, toGroupID);
+                return _weakReference.Target.SwapEntityGroup<T>(id.entityID, id.groupID, (int) toGroupID);
             }
 
             public EGID SwapFirstEntityGroup<T>(int fromGroupID, int toGroupID) where T : IEntityDescriptor, new()
             {
                 return _weakReference.Target.SwapFirstEntityInGroup<T>( fromGroupID, toGroupID);
             }
+
+            public EGID SwapFirstEntityGroup<T>(ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new()
+            {
+                return _weakReference.Target.SwapFirstEntityInGroup<T>( (int) fromGroupID, (int) toGroupID);
+            }
         }
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/EnginesRoot.Submission.cs b/Svelto.ECS/EnginesRoot.Submission.cs
index 8ecd994..7d103f2 100644
--- a/Svelto.ECS/EnginesRoot.Submission.cs
+++ b/Svelto.ECS/EnginesRoot.Submission.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using Svelto.DataStructures.Experimental;
 using Svelto.ECS.Internal;
@@ -19,14 +19,16 @@ namespace Svelto.ECS
             //are there new entities built to process?
             while ( _newEntitiesBuiltToProcess > 0)
             {
-                _newEntitiesBuiltToProcess = 0;
                 //use other as source from now on
                 //current will be use to write new entityViews
                 _groupedEntityToAdd.Swap();
 
-                //Note: if N entity of the same type are added on the same frame the Add callback is called N times on
-                //the same frame. if the Add calback builds a new entity, that entity will not be available in the
-                //database until the N callbacks are done.
+                //Note: if N entity of the same type are added on the same frame
+                //the Add callback is called N times on the same frame.
+                //if the Add calback builds a new entity, that entity will not
+                //be available in the database until the N callbacks are done
+                //solving it could be complicated as callback and database update
+                //must be interleaved.
                 if (_groupedEntityToAdd.other.Count > 0)
                     AddEntityViewsToTheDBAndSuitableEngines(_groupedEntityToAdd.other);
 
@@ -36,6 +38,7 @@ namespace Svelto.ECS
                 if (numberOfReenteringLoops > 5)
                     throw new Exception("possible infinite loop found creating Entities inside IEntityViewsEngine Add method, please consider building entities outside IEntityViewsEngine Add method");
 
+                _newEntitiesBuiltToProcess = 0;
                 numberOfReenteringLoops++;
             }
         }
diff --git a/Svelto.ECS/EntitiesDB.cs b/Svelto.ECS/EntitiesDB.cs
index aa9fa6d..42431a5 100644
--- a/Svelto.ECS/EntitiesDB.cs
+++ b/Svelto.ECS/EntitiesDB.cs
@@ -2,24 +2,18 @@ using System;
 using System.Collections.Generic;
 using Svelto.DataStructures;
 using Svelto.DataStructures.Experimental;
-using Svelto.Utilities;
 
 namespace Svelto.ECS.Internal
 {
-    partial class entitiesDB : IEntitiesDB
+    partial class EntitiesDB : IEntitiesDB
     {
-        internal entitiesDB(Dictionary<int, Dictionary<Type, ITypeSafeDictionary>> groupEntityViewsDB,
+        internal EntitiesDB(Dictionary<int, Dictionary<Type, ITypeSafeDictionary>> groupEntityViewsDB,
             Dictionary<Type, FasterDictionary<int, ITypeSafeDictionary>> groupedGroups)
         {
             _groupEntityViewsDB = groupEntityViewsDB;
             _groupedGroups = groupedGroups;
         }
 
-        public ReadOnlyCollectionStruct<T> QueryEntityViews<T>() where T:class, IEntityStruct
-        {
-            return QueryEntityViews<T>(ExclusiveGroup.StandardEntitiesGroup);
-        }
-
         public ReadOnlyCollectionStruct<T> QueryEntityViews<T>(int @group) where T:class, IEntityStruct
         {
             TypeSafeDictionary<T> typeSafeDictionary;
@@ -28,11 +22,6 @@ namespace Svelto.ECS.Internal
             return typeSafeDictionary.FasterValues;
         }
 
-        public T[] QueryEntities<T>(out int count) where T : IEntityStruct
-        {
-            return QueryEntities<T>(ExclusiveGroup.StandardEntitiesGroup, out count);
-        }
-        
         public T[] QueryEntities<T>(int @group, out int count) where T : IEntityStruct
         {
             TypeSafeDictionary<T> typeSafeDictionary;
@@ -41,12 +30,12 @@ namespace Svelto.ECS.Internal
 
             return typeSafeDictionary.GetFasterValuesBuffer(out count);
         }
-        
-        public EGIDMapper<T> QueryMappedEntities<T>() where T : IEntityStruct
+
+        public T[] QueryEntities<T>(ExclusiveGroup @group, out int targetsCount) where T : IEntityStruct
         {
-            return QueryMappedEntities<T>(ExclusiveGroup.StandardEntitiesGroup);
+            return QueryEntities<T>((int) @group, out targetsCount);
         }
-        
+
         public EGIDMapper<T> QueryMappedEntities<T>(int groupID) where T : IEntityStruct
         {
             TypeSafeDictionary<T> typeSafeDictionary;
@@ -63,6 +52,11 @@ namespace Svelto.ECS.Internal
             return mapper;
         }
 
+        public EGIDMapper<T> QueryMappedEntities<T>(ExclusiveGroup groupID) where T : IEntityStruct
+        {
+            return QueryMappedEntities<T>((int) groupID);
+        }
+
         public T[] QueryEntitiesAndIndex<T>(EGID entityGID, out uint index) where T : IEntityStruct
         {
             T[] array;
@@ -98,11 +92,6 @@ namespace Svelto.ECS.Internal
             return casted != null && casted.ContainsKey(entityGID.entityID);
         }
 
-        public bool HasAny<T>() where T : IEntityStruct
-        {
-            return HasAny<T>(ExclusiveGroup.StandardEntitiesGroup);
-        }
-
         public bool HasAny<T>(int @group) where T : IEntityStruct
         {
             int count;
@@ -110,6 +99,11 @@ namespace Svelto.ECS.Internal
             return count > 0;
         }
 
+        public bool HasAny<T>(ExclusiveGroup @group) where T : IEntityStruct
+        {
+            return HasAny<T>((int) group);
+        }
+
         public bool TryQueryEntityView<T>(EGID entityegid, out T entityView) where T : class, IEntityStruct
         {
             return TryQueryEntityViewInGroupInternal(entityegid, out entityView);
diff --git a/Svelto.ECS/ExclusiveGroups.cs b/Svelto.ECS/ExclusiveGroups.cs
index 2984efd..6c3b906 100644
--- a/Svelto.ECS/ExclusiveGroups.cs
+++ b/Svelto.ECS/ExclusiveGroups.cs
@@ -1,4 +1,4 @@
-namespace Svelto.ECS
+namespace Svelto.ECS
 {
     /// <summary>
     /// Exclusive Groups guarantee that the GroupID is unique.
@@ -13,8 +13,6 @@
     
     public class ExclusiveGroup
     {
-        internal const int StandardEntitiesGroup = int.MaxValue;
-
         public ExclusiveGroup()
         {
             _id       =  _globalId;
diff --git a/Svelto.ECS/ExecuteOnEntitiesDB.cs b/Svelto.ECS/ExecuteOnEntitiesDB.cs
index a32b9d0..aa37e15 100644
--- a/Svelto.ECS/ExecuteOnEntitiesDB.cs
+++ b/Svelto.ECS/ExecuteOnEntitiesDB.cs
@@ -1,10 +1,14 @@
 using Svelto.DataStructures.Experimental;
-using Svelto.Utilities;
 
 namespace Svelto.ECS.Internal
 {
-    partial class entitiesDB
+    partial class EntitiesDB
     {
+        public void ExecuteOnEntity<T>(int id, ExclusiveGroup groupid, EntityAction<T> action) where T : IEntityStruct
+        {
+            ExecuteOnEntity(id, (int)groupid, action);
+        }
+
         public void ExecuteOnEntity<T, W>(EGID entityGID, ref W value, EntityAction<T, W> action) where T : IEntityStruct
         {
             TypeSafeDictionary<T> casted;
@@ -35,49 +39,25 @@ namespace Svelto.ECS.Internal
                                          .FastConcat(entityGID.groupID));
         }
 
-        public void ExecuteOnEntity<T>(int id, EntityAction<T> action) where T : IEntityStruct
-        {
-            ExecuteOnEntity(new EGID(id, ExclusiveGroup.StandardEntitiesGroup), action);
-        }
-
         public void ExecuteOnEntity<T>(int id, int groupid, EntityAction<T> action) where T : IEntityStruct
         {
             ExecuteOnEntity(new EGID(id, groupid), action);
         }
 
-        public void ExecuteOnEntity<T, W>(int id, ref W value, EntityAction<T, W> action) where T : IEntityStruct
-        {
-            ExecuteOnEntity(new EGID(id, ExclusiveGroup.StandardEntitiesGroup), ref value, action);
-        }
-
         public void ExecuteOnEntity<T, W>(int id, int groupid, ref W value, EntityAction<T, W> action)
             where T : IEntityStruct
         {
             ExecuteOnEntity(new EGID(id, groupid), ref value, action);
         }
-        
-        //----------------------------------------------------------------------------------------------------------
 
-        public void ExecuteOnEntities<T>(int groupID, EntitiesAction<T> action) where T : IEntityStruct
+        public void ExecuteOnEntity<T, W>(int id, ExclusiveGroup groupid, ref W value, EntityAction<T, W> action) where T : IEntityStruct
         {
-            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], i);
-
-            SafetyChecks(typeSafeDictionary, count);
+            ExecuteOnEntity(id, (int)groupid, ref value, action);
         }
 
-        public void ExecuteOnEntities<T>(EntitiesAction<T> action) where T : IEntityStruct
-        {
-            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, action);
-        }
+        //----------------------------------------------------------------------------------------------------------
 
-        public void ExecuteOnEntities<T, W>(int groupID, ref W value, EntitiesAction<T, W> action) where T : IEntityStruct
+        public void ExecuteOnEntities<T>(int groupID, EntitiesAction<T> action) where T : IEntityStruct
         {
             int                   count;
             TypeSafeDictionary<T> typeSafeDictionary;
@@ -86,76 +66,38 @@ namespace Svelto.ECS.Internal
             var entities = typeSafeDictionary.GetFasterValuesBuffer(out count);
 
             for (var i = 0; i < count; i++)
-                action(ref entities[i], ref value, i);
+                action(ref entities[i], this, i);
 
             SafetyChecks(typeSafeDictionary, count);
         }
 
-        public void ExecuteOnEntities<T, W>(ref W value, EntitiesAction<T, W> action) where T : IEntityStruct
+        public void ExecuteOnEntities<T>(ExclusiveGroup groupID, EntitiesAction<T> action) where T : IEntityStruct
         {
-            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
+            ExecuteOnEntities((int)groupID, action);
         }
 
-        public void ExecuteOnEntities<T, T1, W>(W value, EntitiesAction<T, T1, W> action)
-            where T : IEntityStruct where T1 : IEntityStruct
-        {
-            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
-        }
-
-        public void ExecuteOnEntities<T, T1>(int group, EntitiesAction<T, T1> 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 map.entities(entities[i].ID, out index)[index], i);
-            }
-
-            SafetyChecks(typeSafeDictionary, count);
-        }
-
-        public void ExecuteOnEntities<T, T1, W>(int group, ref W value, EntitiesAction<T, T1, W> action)
-            where T : IEntityStruct where T1 : IEntityStruct
+        public void ExecuteOnEntities<T, W>(int groupID, ref W value, EntitiesAction<T, W> action) where T : IEntityStruct
         {
             int                   count;
             TypeSafeDictionary<T> typeSafeDictionary;
-            if (QueryEntitySafeDictionary(@group, out typeSafeDictionary) == false) return;
+            if (QueryEntitySafeDictionary(@groupID, 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], ref value, i);
-            }
+                action(ref entities[i], ref value, this, i);
 
             SafetyChecks(typeSafeDictionary, count);
         }
 
-        public void ExecuteOnEntities<T, T1>(EntitiesAction<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct
+        public void ExecuteOnEntities<T, W>(ExclusiveGroup groupID, ref W value, EntitiesAction<T, W> action) where T : IEntityStruct
         {
-            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, action);
+            ExecuteOnEntities((int)groupID, ref value, action);
         }
 
-        public void ExecuteOnEntities<T, T1, W>(ref W value, EntitiesAction<T, T1, W> action)
-            where T : IEntityStruct where T1 : IEntityStruct
-        {
-            ExecuteOnEntities(ExclusiveGroup.StandardEntitiesGroup, ref value, action);
-        }
-        
         //-----------------------------------------------------------------------------------------------------------
         
-        public void ExecuteOnAllEntities<T>(EntityAction<T> action) where T : IEntityStruct
+        public void ExecuteOnAllEntities<T>(ExclusiveGroup[] damageableGroups, AllEntitiesAction<T> action) where T : IEntityStruct
         {
             var                                        type = typeof(T);
             FasterDictionary<int, ITypeSafeDictionary> dic;
@@ -174,14 +116,14 @@ namespace Svelto.ECS.Internal
                     var entities = casted.GetFasterValuesBuffer(out innerCount);
 
                     for (int i = 0; i < innerCount; i++)
-                        action(ref entities[i]);
+                        action(ref entities[i], this);
 
                     SafetyChecks(casted, innerCount);
                 }
             }
         }
 
-        public void ExecuteOnAllEntities<T, W>(ref W value, EntityAction<T, W> action) where T : IEntityStruct
+        public void ExecuteOnAllEntities<T, W>(ref W value, AllEntitiesAction<T, W> action) where T : IEntityStruct
         {
             var                                        type = typeof(T);
             FasterDictionary<int, ITypeSafeDictionary> dic;
@@ -200,13 +142,27 @@ namespace Svelto.ECS.Internal
                     var entities = casted.GetFasterValuesBuffer(out innerCount);
 
                     for (int i = 0; i < innerCount; i++)
-                        action(ref entities[i], ref value);
+                        action(ref entities[i], ref value, this);
 
                     SafetyChecks(casted, innerCount);
                 }
             }
         }
 
+        public void ExecuteOnAllEntities<T>(ExclusiveGroup[] groups, EntitiesAction<T> action) where T : IEntityStruct
+        {
+            foreach (var group in groups)
+            {
+                ExecuteOnEntities(group, action);
+            }
+        }
 
+        public void ExecuteOnAllEntities<T, W>(ExclusiveGroup[] groups, ref W value, EntitiesAction<T, W> action) where T : IEntityStruct
+        {
+            foreach (var group in groups)
+            {
+                ExecuteOnEntities(group, ref value, action);
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/Extensions/Unity/UnitySumbmissionEntityViewScheduler .cs b/Svelto.ECS/Extensions/Unity/UnityEntitySubmissionScheduler.cs
similarity index 63%
rename from Svelto.ECS/Extensions/Unity/UnitySumbmissionEntityViewScheduler .cs
rename to Svelto.ECS/Extensions/Unity/UnityEntitySubmissionScheduler.cs
index 9d66549..fbaa798 100644
--- a/Svelto.ECS/Extensions/Unity/UnitySumbmissionEntityViewScheduler .cs	
+++ b/Svelto.ECS/Extensions/Unity/UnityEntitySubmissionScheduler.cs
@@ -5,17 +5,12 @@ using UnityEngine;
 
 namespace Svelto.ECS.Schedulers.Unity
 {
-    //The EntityViewSubmissionScheduler has been introduced to make
-    //the entityView submission logic platform indipendent.
-    //Please don't be tempted to create your own submission to 
-    //adapt to your game level code design. For example,
-    //you may be tempted to write a submission logic to submit
-    //the entityViews immediatly just because convenient for your game
-    //logic. This is not how it works.
+    //The EntitySubmissionScheduler has been introduced to make the entity views submission logic platform independent
+    //You can customize the scheduler if you wish
     
-    public class UnitySumbmissionEntityViewScheduler : EntitySubmissionScheduler
+    public class UnityEntitySubmissionScheduler : EntitySubmissionScheduler
     {
-        public UnitySumbmissionEntityViewScheduler()
+        public UnityEntitySubmissionScheduler()
         {
             GameObject go = new GameObject("ECSScheduler");
 
diff --git a/Svelto.ECS/IEntitiesDB.cs b/Svelto.ECS/IEntitiesDB.cs
index c5571da..ef3caf3 100644
--- a/Svelto.ECS/IEntitiesDB.cs
+++ b/Svelto.ECS/IEntitiesDB.cs
@@ -4,12 +4,6 @@ namespace Svelto.ECS
 {
     public interface IEntitiesDB
     {
-        /// <summary>
-        /// All the EntityView related methods are left for back compatibility, but
-        /// shouldn't be used anymore. Always pick EntityViewStruct or EntityStruct
-        /// over EntityView
-        /// </summary>
-        ReadOnlyCollectionStruct<T> QueryEntityViews<T>() where T : class, IEntityStruct;
         /// <summary>
         /// All the EntityView related methods are left for back compatibility, but
         /// shouldn't be used anymore. Always pick EntityViewStruct or EntityStruct
@@ -36,8 +30,8 @@ namespace Svelto.ECS
         /// <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 group, out int count) where T : IEntityStruct;
+        T[] QueryEntities<T>(ExclusiveGroup @group, out int targetsCount) 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
@@ -48,7 +42,7 @@ namespace Svelto.ECS
         /// <typeparam name="T"></typeparam>
         /// <returns></returns>
         EGIDMapper<T> QueryMappedEntities<T>(int groupID) where T : IEntityStruct;
-        EGIDMapper<T> QueryMappedEntities<T>() where T : IEntityStruct;
+        EGIDMapper<T> QueryMappedEntities<T>(ExclusiveGroup groupID) 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.
@@ -60,31 +54,22 @@ namespace Svelto.ECS
         /// <param name="action"></param>
         /// <typeparam name="T"></typeparam>
         void ExecuteOnEntities<T>(int groupID, EntitiesAction<T> action) where T : IEntityStruct;
-        void ExecuteOnEntities<T>(EntitiesAction<T> action) where T : IEntityStruct;
+        void ExecuteOnEntities<T>(ExclusiveGroup groupID, EntitiesAction<T> action) where T : IEntityStruct;
         void ExecuteOnEntities<T, W>(int groupID, ref W value, EntitiesAction<T, W> action) where T : IEntityStruct;
-        void ExecuteOnEntities<T, W>(ref W value, EntitiesAction<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, EntitiesAction<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct;
-        void ExecuteOnEntities<T, T1>(EntitiesAction<T, T1> action) where T : IEntityStruct where T1 : IEntityStruct;
-        void ExecuteOnEntities<T, T1, W>(int groupID, ref W value, EntitiesAction<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct;
-        void ExecuteOnEntities<T, T1, W>(ref W value, EntitiesAction<T, T1, W> action) where T : IEntityStruct where T1 : IEntityStruct;
+        void ExecuteOnEntities<T, W>(ExclusiveGroup groupID, ref W value, EntitiesAction<T, W> action) where T : 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="damageableGroups"></param>
         /// <param name="action"></param>
         /// <typeparam name="T"></typeparam>
-        void ExecuteOnAllEntities<T>(EntityAction<T> action) where T : IEntityStruct;
-        void ExecuteOnAllEntities<T, W>(ref W  value, EntityAction<T, W> action) where T : IEntityStruct;
+        void ExecuteOnAllEntities<T>(ExclusiveGroup[] damageableGroups, AllEntitiesAction<T> action) where T : IEntityStruct;
+        void ExecuteOnAllEntities<T, W>(ref W  value, AllEntitiesAction<T, W> action) where T : IEntityStruct;
+        void ExecuteOnAllEntities<T>(ExclusiveGroup[] groups, EntitiesAction<T> action) where T : IEntityStruct;
+        void ExecuteOnAllEntities<T, W>(ExclusiveGroup[] groups, ref W value, EntitiesAction<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
@@ -106,21 +91,24 @@ namespace Svelto.ECS
         /// <param name="action"></param>
         /// <typeparam name="T"></typeparam>
         void ExecuteOnEntity<T>(EGID egid, EntityAction<T> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T>(int     id,   EntityAction<T> action) where T : IEntityStruct;
         void ExecuteOnEntity<T>(int     id,   int          groupid, EntityAction<T>    action) where T : IEntityStruct;
+        void ExecuteOnEntity<T>(int id, ExclusiveGroup groupid, EntityAction<T> action) where T : IEntityStruct;
         void ExecuteOnEntity<T, W>(EGID egid, ref W        value,   EntityAction<T, W> action) where T : IEntityStruct;
-        void ExecuteOnEntity<T, W>(int  id,   ref W        value,   EntityAction<T, W> action) where T : IEntityStruct;
         void ExecuteOnEntity<T, W>(int  id,   int          groupid, ref W           value, EntityAction<T, W> action) where T : IEntityStruct;
+        void ExecuteOnEntity<T, W>(int id, ExclusiveGroup groupid, ref W value, EntityAction<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;
+        bool HasAny<T>(ExclusiveGroup group) where T:IEntityStruct;
     }
 
-    public delegate void EntityAction<T, W>(ref T target, ref W value);
-    public delegate void EntityAction<T>(ref T target);
-    public delegate void EntitiesAction<T, T1, W>(ref T target, ref T1 target1, ref W value, int index);
-    public delegate void EntitiesAction<T, W>(ref T target, ref W value, int index);
-    public delegate void EntitiesAction<T>(ref T target, int index);
+    public delegate void EntityAction<T, W>(ref T target, ref W       value);
+    public delegate void EntityAction<T>(ref    T target);
+
+    public delegate void AllEntitiesAction<T, W>(ref T target, ref W value, IEntitiesDB entitiesDb);
+    public delegate void AllEntitiesAction<T>(ref T target, IEntitiesDB entitiesDb);
+    
+    public delegate void EntitiesAction<T, W>(ref T target, ref W value, IEntitiesDB entitiesDb, int index);
+    public delegate void EntitiesAction<T>(ref T target, IEntitiesDB entitiesDb, int index);
 }
\ No newline at end of file
diff --git a/Svelto.ECS/IEntityFactory.cs b/Svelto.ECS/IEntityFactory.cs
index 1aa7b3c..0b54848 100644
--- a/Svelto.ECS/IEntityFactory.cs
+++ b/Svelto.ECS/IEntityFactory.cs
@@ -22,7 +22,6 @@ namespace Svelto.ECS
         /// </summary>
         /// <typeparam name="T"></typeparam>
         /// <param name="size"></param>
-        void PreallocateEntitySpace<T>(int size) where T : IEntityDescriptor, new();
         void PreallocateEntitySpace<T>(ExclusiveGroup groupID, int size) where T : IEntityDescriptor, new();
         
         /// <summary>
@@ -30,15 +29,7 @@ namespace Svelto.ECS
         ///     itself in terms of EntityViews to build. The Implementors are passed to fill the
         ///     references of the EntityViews components. Please read the articles on my blog
         ///     to understand better the terminologies
-        /// </summary>
-        /// <typeparam name="T"></typeparam>
-        /// <param name="entityID"></param>
-        /// <param name="implementors"></param>
-        EntityStructInitializer BuildEntity<T>(int entityID, object[] implementors) where T:IEntityDescriptor, new();
-
-
-        /// <summary>
-        ///     Using this function is like building a normal entity, but the entityViews
+        ///     Using this function is like building a normal entity, but the entity views
         ///     are grouped by groupID to be more efficently processed inside engines and
         ///     improve cache locality. Either class entityViews and struct entityViews can be
         ///     grouped.
@@ -49,8 +40,6 @@ namespace Svelto.ECS
         /// <param name="implementors"></param>
         EntityStructInitializer BuildEntity<T>(int entityID, ExclusiveGroup groupID, object[] implementors) where T:IEntityDescriptor, new();
         EntityStructInitializer BuildEntity<T>(EGID egid, object[] implementors) where T:IEntityDescriptor, new();
-        
-
         /// <summary>
         ///     When the type of the entity is not known (this is a special case!) an EntityDescriptorInfo
         ///     can be built in place of the generic parameter T.
@@ -60,7 +49,6 @@ namespace Svelto.ECS
         /// <param name="implementors"></param>
         /// 
         EntityStructInitializer BuildEntity(int entityID, ExclusiveGroup groupID, IEntityDescriptor descriptorEntity, object[] implementors);
-        EntityStructInitializer BuildEntity(int entityID, IEntityDescriptor descriptorEntity, object[] implementors);
         EntityStructInitializer BuildEntity(EGID egid, IEntityDescriptor descriptorEntity, object[] implementors);
     }
 }
diff --git a/Svelto.ECS/IEntityFunctions.cs b/Svelto.ECS/IEntityFunctions.cs
index b95b6d1..434fbc2 100644
--- a/Svelto.ECS/IEntityFunctions.cs
+++ b/Svelto.ECS/IEntityFunctions.cs
@@ -7,15 +7,18 @@ namespace Svelto.ECS
         //being entity ID globally not unique, the group must be specified when
         //an entity is removed. Not specificing the group will attempt to remove
         //the entity from the special standard group.
-        void RemoveEntity<T>(int entityID) where T : IEntityDescriptor, new();
         void RemoveEntity<T>(int entityID, int groupID) where T : IEntityDescriptor, new();
+        void RemoveEntity<T>(int entityID, ExclusiveGroup groupID) where T : IEntityDescriptor, new();
         void RemoveEntity<T>(EGID entityegid) where T : IEntityDescriptor, new();
 
         void RemoveGroupAndEntities(int groupID);
+        void RemoveGroupAndEntities(ExclusiveGroup groupID);
         
-        EGID SwapEntityGroup<T>(int entityID, int fromGroupID, int toGroupID = ExclusiveGroup.StandardEntitiesGroup) where T : IEntityDescriptor, new();
-        EGID SwapEntityGroup<T>(EGID id, int toGroupID = ExclusiveGroup.StandardEntitiesGroup) where T : IEntityDescriptor, new();
-        EGID SwapEntityGroup<T>(int entityID, int toGroupID) where T : IEntityDescriptor, new();
-        EGID SwapFirstEntityGroup<T>(int fromGroupID = ExclusiveGroup.StandardEntitiesGroup, int toGroupID = ExclusiveGroup.StandardEntitiesGroup) where T : IEntityDescriptor, new();
+        EGID SwapEntityGroup<T>(int entityID, int fromGroupID, int toGroupID) where T : IEntityDescriptor, new();
+        EGID SwapEntityGroup<T>(int entityID, ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
+        EGID SwapEntityGroup<T>(EGID id, int toGroupID) where T : IEntityDescriptor, new();
+        EGID SwapEntityGroup<T>(EGID id, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
+        EGID SwapFirstEntityGroup<T>(int fromGroupID, int toGroupID) where T : IEntityDescriptor, new();
+        EGID SwapFirstEntityGroup<T>(ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/Profiler/Editor/EngineProfiler/EngineProfilerInspector.cs b/Svelto.ECS/Profiler/Editor/EngineProfiler/EngineProfilerInspector.cs
index ae9f263..882a29a 100644
--- a/Svelto.ECS/Profiler/Editor/EngineProfiler/EngineProfilerInspector.cs
+++ b/Svelto.ECS/Profiler/Editor/EngineProfiler/EngineProfilerInspector.cs
@@ -1,4 +1,4 @@
-#if UNITY_EDITOR
+#if UNITY_EDITOR && ENGINE_PROFILER_ENABLED
 using System;
 using UnityEditor;
 using UnityEngine;
diff --git a/Svelto.ECS/Profiler/Editor/EngineProfiler/EnginesMonitor.cs b/Svelto.ECS/Profiler/Editor/EngineProfiler/EnginesMonitor.cs
index 48ba030..12089ed 100644
--- a/Svelto.ECS/Profiler/Editor/EngineProfiler/EnginesMonitor.cs
+++ b/Svelto.ECS/Profiler/Editor/EngineProfiler/EnginesMonitor.cs
@@ -1,4 +1,4 @@
-#if UNITY_EDITOR
+#if UNITY_EDITOR && ENGINE_PROFILER_ENABLED
 using System.Linq;
 using UnityEditor;
 using UnityEngine;
diff --git a/Svelto.ECS/Profiler/Editor/EngineProfiler/ProfilerEditorLayout.cs b/Svelto.ECS/Profiler/Editor/EngineProfiler/ProfilerEditorLayout.cs
index e9b2044..c3c04b3 100644
--- a/Svelto.ECS/Profiler/Editor/EngineProfiler/ProfilerEditorLayout.cs
+++ b/Svelto.ECS/Profiler/Editor/EngineProfiler/ProfilerEditorLayout.cs
@@ -1,4 +1,4 @@
-#if UNITY_EDITOR
+#if UNITY_EDITOR && ENGINE_PROFILER_ENABLED
 using UnityEditor;
 using UnityEngine;
 
diff --git a/Svelto.ECS/Profiler/Editor/Svelto.ECS.Profiler.asmdef b/Svelto.ECS/Profiler/Editor/Svelto.ECS.Profiler.asmdef
deleted file mode 100644
index 7004a52..0000000
--- a/Svelto.ECS/Profiler/Editor/Svelto.ECS.Profiler.asmdef
+++ /dev/null
@@ -1,13 +0,0 @@
-{
-    "name": "Svelto.ECS.Profiler",
-    "references": [
-        "Svelto.ECS",
-        "Svelto.Common"
-    ],
-    "optionalUnityReferences": [],
-    "includePlatforms": [
-        "Editor"
-    ],
-    "excludePlatforms": [],
-    "allowUnsafeCode": false
-}
\ No newline at end of file