diff --git a/include/xo/procedure2/DPrimitive.hpp b/include/xo/procedure2/DPrimitive.hpp
index 6463ccd..f0e1b5e 100644
--- a/include/xo/procedure2/DPrimitive.hpp
+++ b/include/xo/procedure2/DPrimitive.hpp
@@ -9,6 +9,7 @@
 #include <xo/type/Type.hpp>
 #include <xo/object2/DArray.hpp>
 #include <xo/alloc2/GCObjectConversion.hpp>
+#include <xo/alloc2/GCObjectVisitor.hpp>
 #include <xo/alloc2/GCObject.hpp>
 #include <xo/reflect/Reflect.hpp>
 #include <xo/alloc2/Allocator.hpp>
@@ -76,8 +77,9 @@ namespace xo {
             using Traits = detail::PmFnTraits<Fn>;
 
             using ACollector = xo::mm::ACollector;
-            using AAllocator = xo::mm::AAllocator;
             using AGCObject = xo::mm::AGCObject;
+            using AGCObjectVisitor = xo::mm::AGCObjectVisitor;
+            using AAllocator = xo::mm::AAllocator;
             using DArray = xo::scm::DArray;
             using Reflect = xo::reflect::Reflect;
             using TypeDescr = xo::reflect::TypeDescr;
@@ -134,7 +136,7 @@ namespace xo {
             /** @defgroup scm-primitive-gcobject-facet **/
             ///@{
             Primitive * shallow_move(obj<ACollector> gc) noexcept;
-            void forward_children(obj<ACollector> gc) noexcept;
+            void visit_gco_children(obj<AGCObjectVisitor> gc) noexcept;
             ///@}
 
         private:
@@ -197,11 +199,12 @@ namespace xo {
 
         template <typename Fn>
         void
-        Primitive<Fn>::forward_children(obj<ACollector> gc) noexcept {
-            {
-                auto e = type_.to_facet<AGCObject>();  // FacetRegistry dep
-                gc.forward_inplace(e.iface(), (void **)&(type_.data_));
-            }
+        Primitive<Fn>::visit_gco_children(obj<AGCObjectVisitor> gc) noexcept {
+            gc.visit_poly_child(&type_);
+            //{
+            //    auto e = type_.to_facet<AGCObject>();  // FacetRegistry dep
+            //    gc.forward_inplace(e.iface(), (void **)&(type_.data_));
+            //}
         }
 
     } /*namespace scm*/
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp
index a8b25c9..9d4d338 100644
--- a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_0.hpp
@@ -44,6 +44,7 @@ namespace xo {
             using size_type = xo::mm::AGCObject::size_type;
             using AAllocator = xo::mm::AGCObject::AAllocator;
             using ACollector = xo::mm::AGCObject::ACollector;
+            using AGCObjectVisitor = xo::mm::AGCObject::AGCObjectVisitor;
             using Copaque = xo::mm::AGCObject::Copaque;
             using Opaque = xo::mm::AGCObject::Opaque;
             ///@}
@@ -54,8 +55,10 @@ namespace xo {
             // non-const methods
             /** move instance using allocator **/
             static Opaque shallow_move(DPrimitive_gco_0 & self, obj<ACollector> gc) noexcept;
-            /** during GC: forward immdiate children **/
-            static void forward_children(DPrimitive_gco_0 & self, obj<ACollector> gc) noexcept;
+            /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
+Context: provides address of data pointer so it can be updated in place
+when @p fn invokes garbage collector reentry point **/
+            static void visit_gco_children(DPrimitive_gco_0 & self, obj<AGCObjectVisitor> fn) noexcept;
             ///@}
         };
 
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_1_gco.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_1_gco.hpp
index 89c13e3..6b3e999 100644
--- a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_1_gco.hpp
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_1_gco.hpp
@@ -44,6 +44,7 @@ namespace xo {
             using size_type = xo::mm::AGCObject::size_type;
             using AAllocator = xo::mm::AGCObject::AAllocator;
             using ACollector = xo::mm::AGCObject::ACollector;
+            using AGCObjectVisitor = xo::mm::AGCObject::AGCObjectVisitor;
             using Copaque = xo::mm::AGCObject::Copaque;
             using Opaque = xo::mm::AGCObject::Opaque;
             ///@}
@@ -54,8 +55,10 @@ namespace xo {
             // non-const methods
             /** move instance using allocator **/
             static Opaque shallow_move(DPrimitive_gco_1_gco & self, obj<ACollector> gc) noexcept;
-            /** during GC: forward immdiate children **/
-            static void forward_children(DPrimitive_gco_1_gco & self, obj<ACollector> gc) noexcept;
+            /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
+Context: provides address of data pointer so it can be updated in place
+when @p fn invokes garbage collector reentry point **/
+            static void visit_gco_children(DPrimitive_gco_1_gco & self, obj<AGCObjectVisitor> fn) noexcept;
             ///@}
         };
 
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_dict_string.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_dict_string.hpp
index 24dc877..d54fc0b 100644
--- a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_dict_string.hpp
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_dict_string.hpp
@@ -44,6 +44,7 @@ namespace xo {
             using size_type = xo::mm::AGCObject::size_type;
             using AAllocator = xo::mm::AGCObject::AAllocator;
             using ACollector = xo::mm::AGCObject::ACollector;
+            using AGCObjectVisitor = xo::mm::AGCObject::AGCObjectVisitor;
             using Copaque = xo::mm::AGCObject::Copaque;
             using Opaque = xo::mm::AGCObject::Opaque;
             ///@}
@@ -54,8 +55,10 @@ namespace xo {
             // non-const methods
             /** move instance using allocator **/
             static Opaque shallow_move(DPrimitive_gco_2_dict_string & self, obj<ACollector> gc) noexcept;
-            /** during GC: forward immdiate children **/
-            static void forward_children(DPrimitive_gco_2_dict_string & self, obj<ACollector> gc) noexcept;
+            /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
+Context: provides address of data pointer so it can be updated in place
+when @p fn invokes garbage collector reentry point **/
+            static void visit_gco_children(DPrimitive_gco_2_dict_string & self, obj<AGCObjectVisitor> fn) noexcept;
             ///@}
         };
 
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp
index 51db4ff..eba3197 100644
--- a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_2_gco_gco.hpp
@@ -44,6 +44,7 @@ namespace xo {
             using size_type = xo::mm::AGCObject::size_type;
             using AAllocator = xo::mm::AGCObject::AAllocator;
             using ACollector = xo::mm::AGCObject::ACollector;
+            using AGCObjectVisitor = xo::mm::AGCObject::AGCObjectVisitor;
             using Copaque = xo::mm::AGCObject::Copaque;
             using Opaque = xo::mm::AGCObject::Opaque;
             ///@}
@@ -54,8 +55,10 @@ namespace xo {
             // non-const methods
             /** move instance using allocator **/
             static Opaque shallow_move(DPrimitive_gco_2_gco_gco & self, obj<ACollector> gc) noexcept;
-            /** during GC: forward immdiate children **/
-            static void forward_children(DPrimitive_gco_2_gco_gco & self, obj<ACollector> gc) noexcept;
+            /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
+Context: provides address of data pointer so it can be updated in place
+when @p fn invokes garbage collector reentry point **/
+            static void visit_gco_children(DPrimitive_gco_2_gco_gco & self, obj<AGCObjectVisitor> fn) noexcept;
             ///@}
         };
 
diff --git a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_3_dict_string_gco.hpp b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_3_dict_string_gco.hpp
index 81e0b41..09f9c35 100644
--- a/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_3_dict_string_gco.hpp
+++ b/include/xo/procedure2/detail/IGCObject_DPrimitive_gco_3_dict_string_gco.hpp
@@ -44,6 +44,7 @@ namespace xo {
             using size_type = xo::mm::AGCObject::size_type;
             using AAllocator = xo::mm::AGCObject::AAllocator;
             using ACollector = xo::mm::AGCObject::ACollector;
+            using AGCObjectVisitor = xo::mm::AGCObject::AGCObjectVisitor;
             using Copaque = xo::mm::AGCObject::Copaque;
             using Opaque = xo::mm::AGCObject::Opaque;
             ///@}
@@ -54,8 +55,10 @@ namespace xo {
             // non-const methods
             /** move instance using allocator **/
             static Opaque shallow_move(DPrimitive_gco_3_dict_string_gco & self, obj<ACollector> gc) noexcept;
-            /** during GC: forward immdiate children **/
-            static void forward_children(DPrimitive_gco_3_dict_string_gco & self, obj<ACollector> gc) noexcept;
+            /** Invoke fn.visit_child(iface,data) for each child GCObject pointer.
+Context: provides address of data pointer so it can be updated in place
+when @p fn invokes garbage collector reentry point **/
+            static void visit_gco_children(DPrimitive_gco_3_dict_string_gco & self, obj<AGCObjectVisitor> fn) noexcept;
             ///@}
         };
 
diff --git a/src/procedure2/facet/IGCObject_DPrimitive_gco_0.cpp b/src/procedure2/facet/IGCObject_DPrimitive_gco_0.cpp
index 24a68f6..0819f51 100644
--- a/src/procedure2/facet/IGCObject_DPrimitive_gco_0.cpp
+++ b/src/procedure2/facet/IGCObject_DPrimitive_gco_0.cpp
@@ -21,9 +21,9 @@ namespace xo {
             return self.shallow_move(gc);
         }
         auto
-        IGCObject_DPrimitive_gco_0::forward_children(DPrimitive_gco_0 & self, obj<ACollector> gc) noexcept -> void
+        IGCObject_DPrimitive_gco_0::visit_gco_children(DPrimitive_gco_0 & self, obj<AGCObjectVisitor> fn) noexcept -> void
         {
-            self.forward_children(gc);
+            self.visit_gco_children(fn);
         }
 
     } /*namespace scm*/
diff --git a/src/procedure2/facet/IGCObject_DPrimitive_gco_1_gco.cpp b/src/procedure2/facet/IGCObject_DPrimitive_gco_1_gco.cpp
index 9d411bf..7561d16 100644
--- a/src/procedure2/facet/IGCObject_DPrimitive_gco_1_gco.cpp
+++ b/src/procedure2/facet/IGCObject_DPrimitive_gco_1_gco.cpp
@@ -21,9 +21,9 @@ namespace xo {
             return self.shallow_move(gc);
         }
         auto
-        IGCObject_DPrimitive_gco_1_gco::forward_children(DPrimitive_gco_1_gco & self, obj<ACollector> gc) noexcept -> void
+        IGCObject_DPrimitive_gco_1_gco::visit_gco_children(DPrimitive_gco_1_gco & self, obj<AGCObjectVisitor> fn) noexcept -> void
         {
-            self.forward_children(gc);
+            self.visit_gco_children(fn);
         }
 
     } /*namespace scm*/
diff --git a/src/procedure2/facet/IGCObject_DPrimitive_gco_2_dict_string.cpp b/src/procedure2/facet/IGCObject_DPrimitive_gco_2_dict_string.cpp
index 32c4377..522cba9 100644
--- a/src/procedure2/facet/IGCObject_DPrimitive_gco_2_dict_string.cpp
+++ b/src/procedure2/facet/IGCObject_DPrimitive_gco_2_dict_string.cpp
@@ -21,9 +21,9 @@ namespace xo {
             return self.shallow_move(gc);
         }
         auto
-        IGCObject_DPrimitive_gco_2_dict_string::forward_children(DPrimitive_gco_2_dict_string & self, obj<ACollector> gc) noexcept -> void
+        IGCObject_DPrimitive_gco_2_dict_string::visit_gco_children(DPrimitive_gco_2_dict_string & self, obj<AGCObjectVisitor> fn) noexcept -> void
         {
-            self.forward_children(gc);
+            self.visit_gco_children(fn);
         }
 
     } /*namespace scm*/
diff --git a/src/procedure2/facet/IGCObject_DPrimitive_gco_2_gco_gco.cpp b/src/procedure2/facet/IGCObject_DPrimitive_gco_2_gco_gco.cpp
index 281c426..6f7de39 100644
--- a/src/procedure2/facet/IGCObject_DPrimitive_gco_2_gco_gco.cpp
+++ b/src/procedure2/facet/IGCObject_DPrimitive_gco_2_gco_gco.cpp
@@ -21,9 +21,9 @@ namespace xo {
             return self.shallow_move(gc);
         }
         auto
-        IGCObject_DPrimitive_gco_2_gco_gco::forward_children(DPrimitive_gco_2_gco_gco & self, obj<ACollector> gc) noexcept -> void
+        IGCObject_DPrimitive_gco_2_gco_gco::visit_gco_children(DPrimitive_gco_2_gco_gco & self, obj<AGCObjectVisitor> fn) noexcept -> void
         {
-            self.forward_children(gc);
+            self.visit_gco_children(fn);
         }
 
     } /*namespace scm*/
diff --git a/src/procedure2/facet/IGCObject_DPrimitive_gco_3_dict_string_gco.cpp b/src/procedure2/facet/IGCObject_DPrimitive_gco_3_dict_string_gco.cpp
index b15cc56..aa6c85c 100644
--- a/src/procedure2/facet/IGCObject_DPrimitive_gco_3_dict_string_gco.cpp
+++ b/src/procedure2/facet/IGCObject_DPrimitive_gco_3_dict_string_gco.cpp
@@ -21,9 +21,9 @@ namespace xo {
             return self.shallow_move(gc);
         }
         auto
-        IGCObject_DPrimitive_gco_3_dict_string_gco::forward_children(DPrimitive_gco_3_dict_string_gco & self, obj<ACollector> gc) noexcept -> void
+        IGCObject_DPrimitive_gco_3_dict_string_gco::visit_gco_children(DPrimitive_gco_3_dict_string_gco & self, obj<AGCObjectVisitor> fn) noexcept -> void
         {
-            self.forward_children(gc);
+            self.visit_gco_children(fn);
         }
 
     } /*namespace scm*/