diff -r f55a11cd3b71 -r cff00b3dddf5 src/Pure/update.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/update.scala	Thu Jun 06 22:26:40 2024 +0200
@@ -0,0 +1,41 @@
+/*  Title:      Pure/update.scala
+    Author:     Makarius
+
+Update data (with formal name).
+*/
+
+package isabelle
+
+
+object Update {
+  sealed abstract class Op[A]
+  case class Delete[A](name: String) extends Op[A]
+  case class Insert[A](item: A) extends Op[A]
+
+  def data[A <: Name.T](old_data: Name.Data[A], updates: List[Op[A]]): Name.Data[A] =
+    updates.foldLeft(old_data) {
+      case (map, Delete(name)) => map - name
+      case (map, Insert(item)) => map + (item.name -> item)
+    }
+
+  val empty: Update = Update()
+
+  def make[A](a: Name.Data[A], b: Name.Data[A], kind: Int = 0): Update =
+    if (a eq b) empty
+    else {
+      val delete = List.from(for ((x, y) <- a.iterator if !b.get(x).contains(y)) yield x)
+      val insert = List.from(for ((x, y) <- b.iterator if !a.get(x).contains(y)) yield x)
+      Update(delete = delete, insert = insert, kind = kind)
+    }
+}
+
+sealed case class Update(
+  delete: List[String] = Nil,
+  insert: List[String] = Nil,
+  kind: Int = 0
+) {
+  def deletes: Boolean = delete.nonEmpty
+  def inserts: Boolean = insert.nonEmpty
+  def defined: Boolean = deletes || inserts
+  lazy val domain: Set[String] = delete.toSet ++ insert
+}