Index: boost/property_map/property_map.hpp
===================================================================
--- boost/property_map/property_map.hpp	(revision 60077)
+++ boost/property_map/property_map.hpp	(working copy)
@@ -19,6 +19,8 @@
 #include <boost/concept_archetype.hpp>
 #include <boost/mpl/assert.hpp>
 #include <boost/mpl/or.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/mpl/has_xxx.hpp>
 #include <boost/type_traits/is_same.hpp>
 
 namespace boost {
@@ -26,13 +28,47 @@
   //=========================================================================
   // property_traits class
 
+  BOOST_MPL_HAS_XXX_TRAIT_DEF(key_type);
+  BOOST_MPL_HAS_XXX_TRAIT_DEF(value_type);
+  BOOST_MPL_HAS_XXX_TRAIT_DEF(reference);
+  BOOST_MPL_HAS_XXX_TRAIT_DEF(category);
+ 
+  template<class PA>
+  struct is_property_map :
+    boost::mpl::and_<
+      has_key_type<PA>,
+      has_value_type<PA>,
+      has_reference<PA>,
+      has_category<PA>
+    >
+  {};
+ 
   template <typename PA>
+  struct default_property_traits {
+    typedef typename PA::key_type key_type;
+    typedef typename PA::value_type value_type;
+    typedef typename PA::reference reference;
+    typedef typename PA::category   category;
+  };
+ 
+  struct null_property_traits {};
+ 
+  template <typename PA>
+  struct property_traits :
+    boost::mpl::if_<is_property_map<PA>,
+      default_property_traits<PA>,
+      null_property_traits>::type
+  {};
+
+#if 0
+  template <typename PA>
   struct property_traits {
     typedef typename PA::key_type key_type;
     typedef typename PA::value_type value_type; 
     typedef typename PA::reference reference;
     typedef typename PA::category   category;
   };
+#endif
 
   //=========================================================================
   // property_traits category tags