diff --git a/include/xo/arena/DArenaHashMap.hpp b/include/xo/arena/DArenaHashMap.hpp
index 63741e6..2a51eaa 100644
--- a/include/xo/arena/DArenaHashMap.hpp
+++ b/include/xo/arena/DArenaHashMap.hpp
@@ -16,7 +16,7 @@
 #include <cstring>
 
 namespace xo {
-    namespace mm {
+    namespace map {
 #ifdef NOT_YET
         enum class insert_error : int32_t {
             /** sentinel **/
@@ -654,7 +654,7 @@ namespace xo {
 
             return true;
         }
-    }
+    } /*namespace map*/
 } /*namespace xo*/
 
 /* end DArenaHashMap.hpp */
diff --git a/include/xo/arena/hashmap/ControlGroup.hpp b/include/xo/arena/hashmap/ControlGroup.hpp
index d5db66a..7d3a129 100644
--- a/include/xo/arena/hashmap/ControlGroup.hpp
+++ b/include/xo/arena/hashmap/ControlGroup.hpp
@@ -11,7 +11,7 @@
 #include <cstring>
 
 namespace xo {
-    namespace mm {
+    namespace map {
         namespace detail {
             /** @brief 16x 8-bit control bytes.
              *
@@ -77,7 +77,7 @@ namespace xo {
 #endif
             };
         }
-    } /*namespace mm*/
+    } /*namespace map*/
 } /*namespace xo*/
 
 /* end ControlGroup.hpp */
diff --git a/include/xo/arena/hashmap/DArenaHashMapIterator.hpp b/include/xo/arena/hashmap/DArenaHashMapIterator.hpp
index 285e449..57573b4 100644
--- a/include/xo/arena/hashmap/DArenaHashMapIterator.hpp
+++ b/include/xo/arena/hashmap/DArenaHashMapIterator.hpp
@@ -8,7 +8,7 @@
 #include "hashmap/DArenaHashMapUtil.hpp"
 
 namespace xo {
-    namespace mm {
+    namespace map {
         namespace detail {
 
             template <typename Key,
@@ -76,7 +76,7 @@ namespace xo {
             };
 
         }
-    } /*namespace mm*/
+    } /*namespace map*/
 } /*namespace xo*/
 
 /* end DArenaHashMapIterator.hpp */
diff --git a/include/xo/arena/hashmap/DArenaHashMapUtil.hpp b/include/xo/arena/hashmap/DArenaHashMapUtil.hpp
index 403ff61..f2f72d1 100644
--- a/include/xo/arena/hashmap/DArenaHashMapUtil.hpp
+++ b/include/xo/arena/hashmap/DArenaHashMapUtil.hpp
@@ -8,7 +8,7 @@
 #include <cstdint>
 
 namespace xo {
-    namespace mm {
+    namespace map {
         /** @class DArenaHashMapUtil
          *
          *  @pre
@@ -103,7 +103,7 @@ namespace xo {
                 return std::make_pair(ngx, ng);;
             }
         };
-    } /*namespace mm*/
+    } /*namespace map*/
 } /*namespace xo*/
 
 /* end DArenaHashMapUtil.hpp */
diff --git a/include/xo/arena/hashmap/HashMapStore.hpp b/include/xo/arena/hashmap/HashMapStore.hpp
index 130f4f5..545aa1c 100644
--- a/include/xo/arena/hashmap/HashMapStore.hpp
+++ b/include/xo/arena/hashmap/HashMapStore.hpp
@@ -9,7 +9,7 @@
 #include "hashmap/ControlGroup.hpp"
 
 namespace xo {
-    namespace mm {
+    namespace map {
         namespace detail {
             template <typename Key,
                       typename Value>
@@ -17,6 +17,8 @@ namespace xo {
             public:
                 using value_type = std::pair<const Key, Value>;
                 using group_type = detail::ControlGroup;
+                using control_vector_type = xo::mm::DArenaVector<uint8_t>;
+                using slot_vector_type = xo::mm::DArenaVector<value_type>;
 
             public:
                 /** group_exp2: number of groups {x, 2^x} **/
@@ -26,8 +28,8 @@ namespace xo {
                   n_group_exponent_{group_exp2.first},
                   n_group_{group_exp2.second},
                   n_slot_{group_exp2.second * c_group_size},
-                  control_{DArenaVector<uint8_t>::map(ArenaConfig{.size_ = control_size(n_slot_)})},
-                  slots_{DArenaVector<value_type>::map(ArenaConfig{.size_ = n_slot_ * sizeof(value_type)})}
+                  control_{control_vector_type::map(xo::mm::ArenaConfig{.size_ = control_size(n_slot_)})},
+                  slots_{slot_vector_type::map(xo::mm::ArenaConfig{.size_ = n_slot_ * sizeof(value_type)})}
                 {
                     /* here: arenas have allocated address range, but no committed memory yet */
 
@@ -121,12 +123,12 @@ namespace xo {
                 /** control_[] partitioned into groups of
                  *  c_group_size (16) consecutive elements
                  **/
-                DArenaVector<uint8_t> control_;
+                control_vector_type control_;
                 /** slots_[] holds {key,value} pairs **/
-                DArenaVector<value_type> slots_;
+                slot_vector_type slots_;
             };
         }
-    } /*namespace mm*/
+    } /*namespace map*/
 } /*namespace xo*/
 
 /* end HashMapStore.hpp */
diff --git a/utest/DArenaHashMap.test.cpp b/utest/DArenaHashMap.test.cpp
index 757cd39..088edf2 100644
--- a/utest/DArenaHashMap.test.cpp
+++ b/utest/DArenaHashMap.test.cpp
@@ -11,8 +11,8 @@
 #include <catch2/catch.hpp>
 
 namespace xo {
-    using xo::mm::DArenaHashMapUtil;
-    using xo::mm::DArenaHashMap;
+    using xo::map::DArenaHashMapUtil;
+    using xo::map::DArenaHashMap;
     using xo::rng::random_seed;
     using xo::rng::xoshiro256ss;
     using utest::UtestTools;