Index: trunk/Bookmark.pm
===================================================================
--- trunk/Bookmark.pm	(revision 43)
+++ trunk/Bookmark.pm	(revision 44)
@@ -3,9 +3,14 @@
 use Moose;
 
-has id    => ( is => 'rw' );
+has id    => ( is => 'ro' );
 has uri   => ( is => 'rw' );
 has title => ( is => 'rw' );
-has ctime => ( is => 'rw' );
-has mtime => ( is => 'rw' );
+has ctime => ( is => 'ro' );
+has mtime => (
+    is => 'ro',
+    # mtime defaults to ctime
+    default => sub { $_[0]->ctime },
+    lazy => 1,
+);
 has tags  => ( is => 'rw' );
 has bookmark_uri => ( is => 'rw' );