diff -r 663a927fdc88 -r 1f77110c94ef src/Pure/PIDE/protocol.scala
--- a/src/Pure/PIDE/protocol.scala	Mon Nov 18 09:45:50 2013 +0100
+++ b/src/Pure/PIDE/protocol.scala	Mon Nov 18 17:16:56 2013 +0100
@@ -335,6 +335,7 @@
       def encode_edit(name: Document.Node.Name)
           : T[Document.Node.Edit[Command.Edit, Command.Perspective]] =
         variant(List(
+          // FIXME Document.Node.Blob (!??)
           { case Document.Node.Clear() => (Nil, Nil) },  // FIXME unused !?
           { case Document.Node.Edits(a) => (Nil, list(pair(option(id), option(id)))(a)) },
           { case Document.Node.Deps(header) =>