diff --git a/doublets/src/data/traits.rs b/doublets/src/data/traits.rs
index 2337fbe..00464d4 100644
--- a/doublets/src/data/traits.rs
+++ b/doublets/src/data/traits.rs
@@ -34,7 +34,27 @@ pub trait Links<T: LinkType>: Send + Sync {
     -> Result<Flow, Error<T>>;
 }
 
-pub trait Doublets<T: LinkType>: Links<T> {
+pub trait Doublets<T: LinkType>: Send + Sync {
+    fn constants(&self) -> &LinksConstants<T>;
+
+    fn count_links(&self, query: &[T]) -> T;
+
+    fn create_links(&mut self, query: &[T], handler: WriteHandler<'_, T>)
+    -> Result<Flow, Error<T>>;
+
+    fn each_links(&self, query: &[T], handler: ReadHandler<'_, T>) -> Flow;
+
+    fn update_links(
+        &mut self,
+        query: &[T],
+        change: &[T],
+        handler: WriteHandler<'_, T>,
+    ) -> Result<Flow, Error<T>>;
+
+    fn delete_links(&mut self, query: &[T], handler: WriteHandler<'_, T>)
+    -> Result<Flow, Error<T>>;
+
+    fn get_link(&self, index: T) -> Option<Link<T>>;
     fn count_by(&self, query: impl ToQuery<T>) -> T
     where
         Self: Sized,
@@ -253,8 +273,6 @@ pub trait Doublets<T: LinkType>: Links<T> {
         self.get_link(index).ok_or(Error::NotExists(index))
     }
 
-    fn get_link(&self, index: T) -> Option<Link<T>>;
-
     fn delete_all(&mut self) -> Result<(), Error<T>>
     where
         Self: Sized,
@@ -551,6 +569,37 @@ pub trait Doublets<T: LinkType>: Links<T> {
     }
 }
 
+impl<T: LinkType, D: Doublets<T> + ?Sized> Links<T> for D {
+    fn constants(&self) -> &LinksConstants<T> {
+        self.constants()
+    }
+
+    fn count_links(&self, query: &[T]) -> T {
+        self.count_links(query)
+    }
+
+    fn create_links(&mut self, query: &[T], handler: WriteHandler<'_, T>) -> Result<Flow, Error<T>> {
+        self.create_links(query, handler)
+    }
+
+    fn each_links(&self, query: &[T], handler: ReadHandler<'_, T>) -> Flow {
+        self.each_links(query, handler)
+    }
+
+    fn update_links(
+        &mut self,
+        query: &[T],
+        change: &[T],
+        handler: WriteHandler<'_, T>,
+    ) -> Result<Flow, Error<T>> {
+        self.update_links(query, change, handler)
+    }
+
+    fn delete_links(&mut self, query: &[T], handler: WriteHandler<'_, T>) -> Result<Flow, Error<T>> {
+        self.delete_links(query, handler)
+    }
+}
+
 impl<T: LinkType, All: Doublets<T> + ?Sized> Links<T> for Box<All> {
     fn constants(&self) -> &LinksConstants<T> {
         (**self).constants()
diff --git a/doublets/src/mem/unit/store.rs b/doublets/src/mem/unit/store.rs
index 5231732..3ce99c3 100644
--- a/doublets/src/mem/unit/store.rs
+++ b/doublets/src/mem/unit/store.rs
@@ -321,7 +321,7 @@ impl<T: LinkType, M: RawMem<LinkPart<T>>, TS: UnitTree<T>, TT: UnitTree<T>, TU:
 }
 
 impl<T: LinkType, M: RawMem<LinkPart<T>>, TS: UnitTree<T>, TT: UnitTree<T>, TU: UnitList<T>>
-    Links<T> for Store<T, M, TS, TT, TU>
+    Doublets<T> for Store<T, M, TS, TT, TU>
 {
     fn constants(&self) -> &LinksConstants<T> {
         &self.constants
@@ -552,11 +552,7 @@ impl<T: LinkType, M: RawMem<LinkPart<T>>, TS: UnitTree<T>, TT: UnitTree<T>, TU:
 
         Ok(handler(link, Link::nothing()))
     }
-}
 
-impl<T: LinkType, M: RawMem<LinkPart<T>>, TS: UnitTree<T>, TT: UnitTree<T>, TU: UnitList<T>>
-    Doublets<T> for Store<T, M, TS, TT, TU>
-{
     fn get_link(&self, index: T) -> Option<Link<T>> {
         if self.exists(index) {
             // SAFETY: links is exists