diff --git a/.gitmodules b/.gitmodules
index e69de29..532d6f0 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "Svelto.Common"]
+	path = Svelto.Common
+	url = https://github.com/sebas77/Svelto.Common.git
diff --git a/Svelto.Common b/Svelto.Common
index a1f5f55..5b756d5 160000
--- a/Svelto.Common
+++ b/Svelto.Common
@@ -1 +1 @@
-Subproject commit a1f5f55c8b28f66ed033fa02c425dfa16c3c30e6
+Subproject commit 5b756d57920c83a8e31dad9eedee8b629c6cb245
diff --git a/Svelto.ECS/DataStructures/TypeSafeDictionary.cs b/Svelto.ECS/DataStructures/TypeSafeDictionary.cs
index 00480be..ef83f92 100644
--- a/Svelto.ECS/DataStructures/TypeSafeDictionary.cs
+++ b/Svelto.ECS/DataStructures/TypeSafeDictionary.cs
@@ -115,22 +115,30 @@ namespace Svelto.ECS.Internal
             return new TypeSafeDictionary<TValue>();
         }
         
-        public void ExecuteOnEntityView<W>(int entityGidEntityId, ref W value, ActionRef<TValue, W> action)
+        public bool ExecuteOnEntityView<W>(int entityGidEntityId, ref W value, ActionRef<TValue, W> action)
         {
             uint findIndex;
             if (FindIndex(entityGidEntityId, out findIndex))
             {
                 action(ref _values[findIndex], ref value);
+
+                return true;
             }
+
+            return false;
         }
         
-        public void ExecuteOnEntityView(int entityGidEntityId, ActionRef<TValue> action)
+        public bool ExecuteOnEntityView(int entityGidEntityId, ActionRef<TValue> action)
         {
             uint findIndex;
             if (FindIndex(entityGidEntityId, out findIndex))
             {
                 action(ref _values[findIndex]);
+                
+                return true;
             }
+
+            return false;
         }
         
         public uint FindElementIndex(int entityGidEntityId)
diff --git a/Svelto.ECS/EntitiesDB.cs b/Svelto.ECS/EntitiesDB.cs
index 7619fd4..3a0712e 100644
--- a/Svelto.ECS/EntitiesDB.cs
+++ b/Svelto.ECS/EntitiesDB.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Security.Principal;
 using Svelto.DataStructures;
 using Svelto.Utilities;
 
@@ -75,11 +74,20 @@ namespace Svelto.ECS.Internal
             return QueryEntities<T>(entityGID.groupID, out count);
         }
 
+        public bool TryQueryEntitiesAndIndex<T>(EGID entityGid, out uint index, out T[] array) where T : IEntityStruct
+        {
+            if ((array = QueryEntitiesAndIndex<T>(entityGid, out index)) != null)
+                return true;
+            
+            return false;
+        }
+
         public T QueryEntityView<T>(EGID entityGID) where T : class, IEntityStruct
         {
             T entityView;
 
-            TryQueryEntityViewInGroup(entityGID, out entityView);
+            if (TryQueryEntityViewInGroup(entityGID, out entityView) == false)
+                throw new Exception("Entity not found id: ".FastConcat(entityGID.entityID).FastConcat(" groupID: ").FastConcat(entityGID.groupID));
 
             return entityView;
         }
@@ -87,19 +95,27 @@ namespace Svelto.ECS.Internal
         public void ExecuteOnEntity<T, W>(EGID entityGID, ref W value, ActionRef<T, W> action) where T : IEntityStruct
         {
             TypeSafeDictionary<T> casted;
-            if (!FindSafeDictionary(entityGID, out casted)) return;
+            if (FindSafeDictionary(entityGID, out casted))
+            {
+                if (casted != null)
+                    if (casted.ExecuteOnEntityView(entityGID.entityID, ref value, action) == true)
+                        return;
+            }
 
-            if (casted != null)
-                casted.ExecuteOnEntityView(entityGID.entityID, ref value, action);
+            throw new Exception("Entity not found id: ".FastConcat(entityGID.entityID).FastConcat(" groupID: ").FastConcat(entityGID.groupID));
         }
         
         public void ExecuteOnEntity<T>(EGID entityGID, ActionRef<T> action) where T : IEntityStruct
         {
             TypeSafeDictionary<T> casted;
-            if (!FindSafeDictionary(entityGID, out casted)) return;
+            if (FindSafeDictionary(entityGID, out casted))
+            {
+                if (casted != null)
+                    if (casted.ExecuteOnEntityView(entityGID.entityID, action) == true)
+                        return;
+            }
 
-            if (casted != null)
-                casted.ExecuteOnEntityView(entityGID.entityID, action);
+            throw new Exception("Entity not found id: ".FastConcat(entityGID.entityID).FastConcat(" groupID: ").FastConcat(entityGID.groupID));
         }
 
         public void ExecuteOnEntity<T>(int id, ActionRef<T> action) where T : IEntityStruct
diff --git a/Svelto.ECS/EntityViewUtility.cs b/Svelto.ECS/EntityViewUtility.cs
index 1fe591b..33d1840 100644
--- a/Svelto.ECS/EntityViewUtility.cs
+++ b/Svelto.ECS/EntityViewUtility.cs
@@ -52,7 +52,7 @@ static class EntityViewUtility
 #if DEBUG && !PROFILER
             else
             {
-                Utility.Console.LogError(NULL_IMPLEMENTOR_ERROR.FastConcat("Type ", entityDescriptorName, " entityView ", entityBuilder.GetEntityType().ToString()));
+                Utility.Console.Log(NULL_IMPLEMENTOR_ERROR.FastConcat("Type ", entityDescriptorName, " entityView ", entityBuilder.GetEntityType().ToString()));
             }
 #endif
         }
diff --git a/Svelto.ECS/ExclusiveGroups.cs b/Svelto.ECS/ExclusiveGroups.cs
index e02a001..d9c6980 100644
--- a/Svelto.ECS/ExclusiveGroups.cs
+++ b/Svelto.ECS/ExclusiveGroups.cs
@@ -6,7 +6,14 @@
 
         public ExclusiveGroup()
         {
-            _id = _globalId++;
+            _id       =  _globalId;
+            _globalId += 1;
+        }
+
+        public ExclusiveGroup(int range)
+        {
+            _id       =  _globalId;
+            _globalId += range;
         }
         
         public static explicit operator int(ExclusiveGroup group) // explicit byte to digit conversion operator
@@ -15,6 +22,6 @@
         }
 
         readonly int _id;
-        static int _globalId;
+        static   int _globalId;
     }
 }
\ No newline at end of file
diff --git a/Svelto.ECS/IEntitiesDB.cs b/Svelto.ECS/IEntitiesDB.cs
index 8efd084..54fdcdd 100644
--- a/Svelto.ECS/IEntitiesDB.cs
+++ b/Svelto.ECS/IEntitiesDB.cs
@@ -33,7 +33,9 @@ namespace Svelto.ECS
         //to use with EntityViews, EntityStructs and EntityViewStructs
         T[] QueryEntities<T>(out int count) where T : IEntityStruct;
         T[] QueryEntities<T>(int group, out int count) 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, W>(EGID egid, ref W value, ActionRef<T, W> action) where T : IEntityStruct;
diff --git a/Svelto.ECS/StaticEntityDescriptorInfo.cs b/Svelto.ECS/StaticEntityDescriptorInfo.cs
index 47c43cf..8e85a32 100644
--- a/Svelto.ECS/StaticEntityDescriptorInfo.cs
+++ b/Svelto.ECS/StaticEntityDescriptorInfo.cs
@@ -23,7 +23,7 @@ namespace Svelto.ECS
         public static readonly StaticEntityDescriptorInfo<TType> descriptor = new StaticEntityDescriptorInfo<TType>(new TType());
     }
 
-    public struct DynamicEntityDescriptorInfo<TType> where TType : IEntityDescriptor, new()
+    public struct DynamicEntityDescriptorInfo<TType>:IEntityDescriptor where TType : IEntityDescriptor, new()
     {
         public DynamicEntityDescriptorInfo(FasterList<IEntityBuilder> extraEntityViews) : this()
         {
@@ -42,7 +42,7 @@ namespace Svelto.ECS
         public IEntityBuilder[] entitiesToBuild { get; private set; }
     }
 
-    public struct StaticEntityDescriptorInfo<TType> where TType : IEntityDescriptor
+    public struct StaticEntityDescriptorInfo<TType>: IEntityDescriptor where TType : IEntityDescriptor
     {
         internal StaticEntityDescriptorInfo(TType descriptor) : this()
         {