--- a/src/rcldb/rcldb.h
+++ b/src/rcldb/rcldb.h
@@ -55,6 +55,15 @@
 #ifndef NO_NAMESPACES
 namespace Rcl {
 #endif
+
+// Omega compatible values. We leave a hole for future omega values. Not sure 
+// it makes any sense to keep any level of omega compat given that the index
+// is incompatible anyway.
+enum value_slot {
+    VALUE_LASTMOD = 0,	// 4 byte big endian value - seconds since 1970.
+    VALUE_MD5 = 1,	// 16 byte MD5 checksum of original document.
+    VALUE_SIG = 10      // Doc sig as chosen by app (ex: mtime+size
+};
 
 class SearchData;
 class TermIter;