ADDED   polemy/layer.d
Index: polemy/layer.d
==================================================================
--- polemy/layer.d
+++ polemy/layer.d
@@ -0,0 +1,20 @@
+/**
+ * Authors: k.inaba
+ * License: NYSL 0.9982 http://www.kmonos.net/nysl/
+ *
+ * Definition of constants related to the layers.
+ */
+module polemy.layer;
+import polemy._common;
+import polemy.failure;
+
+/// Type for the layer ID
+
+alias string Layer;
+
+enum : Layer
+{
+	SystemLayer = "(system)", /// Predefined layer for internal data
+	ValueLayer  = "@value",   /// Predefined layer for normal run
+	MacroLayer  = "@macro",   /// Predefined layer for macro run
+}