diff --git a/src/Builtin/Aspects.cs b/src/Builtin/Aspects.cs
index 6d93f84..9f552c9 100644
--- a/src/Builtin/Aspects.cs
+++ b/src/Builtin/Aspects.cs
@@ -146,7 +146,7 @@
         public static EcsSpan Where<TCollection, A0, A1>(this TCollection entities, out A0 a0, out A1 a1)
             where A0 : EcsAspect
             where A1 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out a0, out a1);
         }
@@ -171,7 +171,7 @@
             where A0 : EcsAspect
             where A1 : EcsAspect
             where A2 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out a0, out a1, out a2);
         }
@@ -199,7 +199,7 @@
             where A1 : EcsAspect
             where A2 : EcsAspect
             where A3 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out a0, out a1, out a2, out a3);
         }
@@ -230,7 +230,7 @@
             where A2 : EcsAspect
             where A3 : EcsAspect
             where A4 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out a0, out a1, out a2, out a3, out a4);
         }
@@ -264,7 +264,7 @@
             where A3 : EcsAspect
             where A4 : EcsAspect
             where A5 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out a0, out a1, out a2, out a3, out a4, out a5);
         }
@@ -296,7 +296,7 @@
         public static EcsReadonlyGroup WhereToGroup<TCollection, A0, A1>(this TCollection entities, out A0 a0, out A1 a1)
             where A0 : EcsAspect
             where A1 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out a0, out a1);
         }
@@ -321,7 +321,7 @@
             where A0 : EcsAspect
             where A1 : EcsAspect
             where A2 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out a0, out a1, out a2);
         }
@@ -349,7 +349,7 @@
             where A1 : EcsAspect
             where A2 : EcsAspect
             where A3 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out a0, out a1, out a2, out a3);
         }
@@ -380,7 +380,7 @@
             where A2 : EcsAspect
             where A3 : EcsAspect
             where A4 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out a0, out a1, out a2, out a3, out a4);
         }
@@ -414,7 +414,7 @@
             where A3 : EcsAspect
             where A4 : EcsAspect
             where A5 : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out a0, out a1, out a2, out a3, out a4, out a5);
         }
diff --git a/src/Builtin/Worlds.cs b/src/Builtin/Worlds.cs
index d98a1db..9e7fbc0 100644
--- a/src/Builtin/Worlds.cs
+++ b/src/Builtin/Worlds.cs
@@ -1,11 +1,11 @@
 namespace DCFApixels.DragonECS
 {
-    public sealed class EcsDefaultWorld : EcsWorld
+    public sealed class EcsDefaultWorld : EcsWorld, IEntityStorage
     {
         public EcsDefaultWorld() : base(null) { }
         public EcsDefaultWorld(IEcsWorldConfig config) : base(config) { }
     }
-    public sealed class EcsEventWorld : EcsWorld
+    public sealed class EcsEventWorld : EcsWorld, IEntityStorage
     {
         public EcsEventWorld() : base(null) { }
         public EcsEventWorld(IEcsWorldConfig config) : base(config) { }
diff --git a/src/Collections/EcsGroup.cs b/src/Collections/EcsGroup.cs
index 2d2a281..f2a3603 100644
--- a/src/Collections/EcsGroup.cs
+++ b/src/Collections/EcsGroup.cs
@@ -144,7 +144,7 @@ namespace DCFApixels.DragonECS
     }
 
     [DebuggerTypeProxy(typeof(DebuggerProxy))]
-    public unsafe class EcsGroup : IDisposable, IEnumerable<int>, IEntitiesCollection
+    public unsafe class EcsGroup : IDisposable, IEnumerable<int>, IEntityStorage
     {
         private EcsWorld _source;
         private int[] _dense;
diff --git a/src/EcsWorld.cs b/src/EcsWorld.cs
index 2c485a7..c4e725a 100644
--- a/src/EcsWorld.cs
+++ b/src/EcsWorld.cs
@@ -6,7 +6,7 @@ using System.Runtime.CompilerServices;
 
 namespace DCFApixels.DragonECS
 {
-    public abstract partial class EcsWorld: IEntitiesCollection
+    public abstract partial class EcsWorld: IEntityStorage
     {
         public readonly short id;
         private IEcsWorldConfig _config;
@@ -26,6 +26,8 @@ namespace DCFApixels.DragonECS
         private int _freeSpace;
         private bool _isEnableAutoReleaseDelEntBuffer = true;
 
+        private long _version = 0;
+
         private List<WeakReference<EcsGroup>> _groups = new List<WeakReference<EcsGroup>>();
         private Stack<EcsGroup> _groupsPool = new Stack<EcsGroup>(64);
 
diff --git a/src/Executors/Queries.cs b/src/Executors/Queries.cs
index 692f860..ba3062c 100644
--- a/src/Executors/Queries.cs
+++ b/src/Executors/Queries.cs
@@ -1,6 +1,6 @@
 namespace DCFApixels.DragonECS
 {
-    public interface IEntitiesCollection
+    public interface IEntityStorage
     {
         EcsSpan ToSpan();
     }
@@ -9,7 +9,7 @@
         #region Where
         public static EcsSpan Where<TCollection, TAspect>(this TCollection entities, out TAspect aspect)
             where TAspect : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().Where(out aspect);
         }
@@ -58,7 +58,7 @@
         #region WhereToGroup
         public static EcsReadonlyGroup WhereToGroup<TCollection ,TAspect>(this TCollection entities, out TAspect aspect)
             where TAspect : EcsAspect
-            where TCollection : IEntitiesCollection
+            where TCollection : IEntityStorage
         {
             return entities.ToSpan().WhereToGroup(out aspect);
         }