diff -r bce98b5dfec6 -r c7a98469c0e7 src/Pure/Build/export_theory.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/Build/export_theory.scala	Sat Jan 20 15:07:41 2024 +0100
@@ -0,0 +1,763 @@
+/*  Title:      Pure/Build/export_theory.scala
+    Author:     Makarius
+
+Export foundational theory content.
+*/
+
+package isabelle
+
+
+import scala.collection.immutable.SortedMap
+
+
+object Export_Theory {
+  /** session content **/
+
+  sealed case class Session(name: String, theory_graph: Graph[String, Option[Theory]]) {
+    override def toString: String = name
+
+    def theory(theory_name: String): Option[Theory] =
+      if (theory_graph.defined(theory_name)) theory_graph.get_node(theory_name)
+      else None
+
+    def theories: List[Theory] =
+      theory_graph.topological_order.flatMap(theory)
+  }
+
+  def read_session(
+    session_context: Export.Session_Context,
+    session_stack: Boolean = false,
+    progress: Progress = new Progress
+  ): Session = {
+    val thys =
+      for (theory <- theory_names(session_context, session_stack = session_stack)) yield {
+        progress.echo("Reading theory " + theory)
+        read_theory(session_context.theory(theory))
+      }
+
+    val graph0 =
+      thys.foldLeft(Graph.string[Option[Theory]]) {
+        case (g, thy) => g.default_node(thy.name, Some(thy))
+      }
+    val graph1 =
+      thys.foldLeft(graph0) {
+        case (g0, thy) =>
+          thy.parents.foldLeft(g0) {
+            case (g1, parent) => g1.default_node(parent, None).add_edge_acyclic(parent, thy.name)
+          }
+      }
+
+    Session(session_context.session_name, graph1)
+  }
+
+
+
+  /** theory content **/
+
+  sealed case class Theory(name: String, parents: List[String],
+    types: List[Entity[Type]],
+    consts: List[Entity[Const]],
+    axioms: List[Entity[Axiom]],
+    thms: List[Entity[Thm]],
+    classes: List[Entity[Class]],
+    locales: List[Entity[Locale]],
+    locale_dependencies: List[Entity[Locale_Dependency]],
+    classrel: List[Classrel],
+    arities: List[Arity],
+    constdefs: List[Constdef],
+    typedefs: List[Typedef],
+    datatypes: List[Datatype],
+    spec_rules: List[Spec_Rule],
+    others: Map[String, List[Entity[Other]]]
+  ) {
+    override def toString: String = name
+
+    def entity_iterator: Iterator[Entity0] =
+      types.iterator.map(_.no_content) ++
+      consts.iterator.map(_.no_content) ++
+      axioms.iterator.map(_.no_content) ++
+      thms.iterator.map(_.no_content) ++
+      classes.iterator.map(_.no_content) ++
+      locales.iterator.map(_.no_content) ++
+      locale_dependencies.iterator.map(_.no_content) ++
+      (for { (_, xs) <- others; x <- xs.iterator } yield x.no_content)
+
+    def cache(cache: Term.Cache): Theory =
+      Theory(cache.string(name),
+        parents.map(cache.string),
+        types.map(_.cache(cache)),
+        consts.map(_.cache(cache)),
+        axioms.map(_.cache(cache)),
+        thms.map(_.cache(cache)),
+        classes.map(_.cache(cache)),
+        locales.map(_.cache(cache)),
+        locale_dependencies.map(_.cache(cache)),
+        classrel.map(_.cache(cache)),
+        arities.map(_.cache(cache)),
+        constdefs.map(_.cache(cache)),
+        typedefs.map(_.cache(cache)),
+        datatypes.map(_.cache(cache)),
+        spec_rules.map(_.cache(cache)),
+        (for ((k, xs) <- others.iterator) yield cache.string(k) -> xs.map(_.cache(cache))).toMap)
+  }
+
+  def read_theory_parents(theory_context: Export.Theory_Context): Option[List[String]] =
+    theory_context.get(Export.THEORY_PREFIX + "parents")
+      .map(entry => Library.trim_split_lines(entry.text))
+
+  def theory_names(
+    session_context: Export.Session_Context,
+    session_stack: Boolean = false
+  ): List[String] = {
+    val session = if (session_stack) "" else session_context.session_name
+    for {
+      theory <- session_context.theory_names(session = session)
+      if read_theory_parents(session_context.theory(theory)).isDefined
+    } yield theory
+  }
+
+  def no_theory: Theory =
+    Theory("", Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Nil, Map.empty)
+
+  def read_theory(
+    theory_context: Export.Theory_Context,
+    permissive: Boolean = false
+  ): Theory = {
+    val cache = theory_context.cache
+    val session_name = theory_context.session_context.session_name
+    val theory_name = theory_context.theory
+    read_theory_parents(theory_context) match {
+      case None if permissive => no_theory
+      case None =>
+        error("Missing theory export in session " + quote(session_name) + ": " + quote(theory_name))
+      case Some(parents) =>
+        val theory =
+          Theory(theory_name, parents,
+            read_types(theory_context),
+            read_consts(theory_context),
+            read_axioms(theory_context),
+            read_thms(theory_context),
+            read_classes(theory_context),
+            read_locales(theory_context),
+            read_locale_dependencies(theory_context),
+            read_classrel(theory_context),
+            read_arities(theory_context),
+            read_constdefs(theory_context),
+            read_typedefs(theory_context),
+            read_datatypes(theory_context),
+            read_spec_rules(theory_context),
+            read_others(theory_context))
+        if (cache.no_cache) theory else theory.cache(cache)
+    }
+  }
+
+
+  /* entities */
+
+  object Kind {
+    val TYPE = "type"
+    val CONST = "const"
+    val THM = "thm"
+    val PROOF = "proof"
+    val LOCALE_DEPENDENCY = "locale_dependency"
+    val DOCUMENT_HEADING = "document_heading"
+    val DOCUMENT_TEXT = "document_text"
+    val PROOF_TEXT = "proof_text"
+  }
+
+  def export_kind(kind: String): String =
+    if (kind == Markup.TYPE_NAME) Kind.TYPE
+    else if (kind == Markup.CONSTANT) Kind.CONST
+    else kind
+
+  def export_kind_name(kind: String, name: String): String =
+    name + "|" + export_kind(kind)
+
+  abstract class Content[T] {
+    def cache(cache: Term.Cache): T
+  }
+  sealed case class No_Content() extends Content[No_Content] {
+    def cache(cache: Term.Cache): No_Content = this
+  }
+  sealed case class Entity[A <: Content[A]](
+    kind: String,
+    name: String,
+    xname: String,
+    pos: Position.T,
+    id: Option[Long],
+    serial: Long,
+    content: Option[A]
+  ) {
+    val kname: String = export_kind_name(kind, name)
+    val range: Symbol.Range = Position.Range.unapply(pos).getOrElse(Text.Range.offside)
+    val file: String = Position.File.unapply(pos).getOrElse("")
+
+    def export_kind: String = Export_Theory.export_kind(kind)
+    override def toString: String = export_kind + " " + quote(name)
+
+    def the_content: A =
+      if (content.isDefined) content.get else error("No content for " + toString)
+
+    def no_content: Entity0 = copy(content = None)
+
+    def cache(cache: Term.Cache): Entity[A] =
+      Entity(
+        cache.string(kind),
+        cache.string(name),
+        cache.string(xname),
+        cache.position(pos),
+        id,
+        serial,
+        content.map(_.cache(cache)))
+  }
+  type Entity0 = Entity[No_Content]
+
+  def read_entities[A <: Content[A]](
+    theory_context: Export.Theory_Context,
+    export_name: String,
+    kind: String,
+    decode: XML.Decode.T[A]
+  ): List[Entity[A]] = {
+    def decode_entity(tree: XML.Tree): Entity[A] = {
+      def err(): Nothing = throw new XML.XML_Body(List(tree))
+
+      tree match {
+        case XML.Elem(Markup(Markup.ENTITY, props), body) =>
+          val name = Markup.Name.unapply(props) getOrElse err()
+          val xname = Markup.XName.unapply(props) getOrElse err()
+          val pos = props.filter(p => Markup.position_property(p) && p._1 != Markup.ID)
+          val id = Position.Id.unapply(props)
+          val serial = Markup.Serial.unapply(props) getOrElse err()
+          val content = if (body.isEmpty) None else Some(decode(body))
+          Entity(kind, name, xname, pos, id, serial, content)
+        case _ => err()
+      }
+    }
+    theory_context.yxml(export_name).map(decode_entity)
+  }
+
+
+  /* approximative syntax */
+
+  enum Assoc { case NO_ASSOC, LEFT_ASSOC, RIGHT_ASSOC }
+
+  sealed abstract class Syntax
+  case object No_Syntax extends Syntax
+  case class Prefix(delim: String) extends Syntax
+  case class Infix(assoc: Assoc, delim: String, pri: Int) extends Syntax
+
+  def decode_syntax: XML.Decode.T[Syntax] =
+    XML.Decode.variant(List(
+      { case (Nil, Nil) => No_Syntax },
+      { case (List(delim), Nil) => Prefix(delim) },
+      { case (Nil, body) =>
+          import XML.Decode._
+          val (ass, delim, pri) = triple(int, string, int)(body)
+          Infix(Assoc.fromOrdinal(ass), delim, pri) }))
+
+
+  /* types */
+
+  sealed case class Type(syntax: Syntax, args: List[String], abbrev: Option[Term.Typ])
+  extends Content[Type] {
+    override def cache(cache: Term.Cache): Type =
+      Type(
+        syntax,
+        args.map(cache.string),
+        abbrev.map(cache.typ))
+  }
+
+  def read_types(theory_context: Export.Theory_Context): List[Entity[Type]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "types", Markup.TYPE_NAME,
+      { body =>
+        import XML.Decode._
+        val (syntax, args, abbrev) =
+          triple(decode_syntax, list(string), option(Term_XML.Decode.typ))(body)
+        Type(syntax, args, abbrev)
+      })
+
+
+  /* consts */
+
+  sealed case class Const(
+    syntax: Syntax,
+    typargs: List[String],
+    typ: Term.Typ,
+    abbrev: Option[Term.Term],
+    propositional: Boolean
+  ) extends Content[Const] {
+    override def cache(cache: Term.Cache): Const =
+      Const(
+        syntax,
+        typargs.map(cache.string),
+        cache.typ(typ),
+        abbrev.map(cache.term),
+        propositional)
+  }
+
+  def read_consts(theory_context: Export.Theory_Context): List[Entity[Const]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "consts", Markup.CONSTANT,
+      { body =>
+        import XML.Decode._
+        val (syntax, (typargs, (typ, (abbrev, propositional)))) =
+          pair(decode_syntax,
+            pair(list(string),
+              pair(Term_XML.Decode.typ,
+                pair(option(Term_XML.Decode.term), bool))))(body)
+        Const(syntax, typargs, typ, abbrev, propositional)
+      })
+
+
+  /* axioms */
+
+  sealed case class Prop(
+    typargs: List[(String, Term.Sort)],
+    args: List[(String, Term.Typ)],
+    term: Term.Term
+  ) extends Content[Prop] {
+    override def cache(cache: Term.Cache): Prop =
+      Prop(
+        typargs.map({ case (name, sort) => (cache.string(name), cache.sort(sort)) }),
+        args.map({ case (name, typ) => (cache.string(name), cache.typ(typ)) }),
+        cache.term(term))
+  }
+
+  def decode_prop(body: XML.Body): Prop = {
+    val (typargs, args, t) = {
+      import XML.Decode._
+      import Term_XML.Decode._
+      triple(list(pair(string, sort)), list(pair(string, typ)), term)(body)
+    }
+    Prop(typargs, args, t)
+  }
+
+  sealed case class Axiom(prop: Prop) extends Content[Axiom] {
+    override def cache(cache: Term.Cache): Axiom = Axiom(prop.cache(cache))
+  }
+
+  def read_axioms(theory_context: Export.Theory_Context): List[Entity[Axiom]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "axioms", Markup.AXIOM,
+      body => Axiom(decode_prop(body)))
+
+
+  /* theorems */
+
+  sealed case class Thm_Id(serial: Long, theory_name: String)
+
+  sealed case class Thm(
+    prop: Prop,
+    deps: List[String],
+    proof: Term.Proof)
+  extends Content[Thm] {
+    override def cache(cache: Term.Cache): Thm =
+      Thm(
+        prop.cache(cache),
+        deps.map(cache.string),
+        cache.proof(proof))
+  }
+
+  def read_thms(theory_context: Export.Theory_Context): List[Entity[Thm]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "thms", Kind.THM,
+      { body =>
+        import XML.Decode._
+        import Term_XML.Decode._
+        val (prop, deps, prf) = triple(decode_prop, list(string), proof)(body)
+        Thm(prop, deps, prf)
+      })
+
+  sealed case class Proof(
+    typargs: List[(String, Term.Sort)],
+    args: List[(String, Term.Typ)],
+    term: Term.Term,
+    proof: Term.Proof
+  ) {
+    def prop: Prop = Prop(typargs, args, term)
+
+    def cache(cache: Term.Cache): Proof =
+      Proof(
+        typargs.map({ case (name, sort) => (cache.string(name), cache.sort(sort)) }),
+        args.map({ case (name, typ) => (cache.string(name), cache.typ(typ)) }),
+        cache.term(term),
+        cache.proof(proof))
+  }
+
+  def read_proof(
+    session_context: Export.Session_Context,
+    id: Thm_Id,
+    other_cache: Option[Term.Cache] = None
+  ): Option[Proof] = {
+    val theory_context = session_context.theory(id.theory_name, other_cache = other_cache)
+    val cache = theory_context.cache
+
+    for { entry <- theory_context.get(Export.PROOFS_PREFIX + id.serial) }
+    yield {
+      val body = entry.yxml
+      val (typargs, (args, (prop_body, proof_body))) = {
+        import XML.Decode._
+        import Term_XML.Decode._
+        pair(list(pair(string, sort)), pair(list(pair(string, typ)), pair(x => x, x => x)))(body)
+      }
+      val env = args.toMap
+      val prop = Term_XML.Decode.term_env(env)(prop_body)
+      val proof = Term_XML.Decode.proof_env(env)(proof_body)
+
+      val result = Proof(typargs, args, prop, proof)
+      if (cache.no_cache) result else result.cache(cache)
+    }
+  }
+
+  def read_proof_boxes(
+    session_context: Export.Session_Context,
+    proof: Term.Proof,
+    suppress: Thm_Id => Boolean = _ => false,
+    other_cache: Option[Term.Cache] = None
+  ): List[(Thm_Id, Proof)] = {
+    var seen = Set.empty[Long]
+    var result = SortedMap.empty[Long, (Thm_Id, Proof)]
+
+    def boxes(context: Option[(Long, Term.Proof)], prf: Term.Proof): Unit = {
+      prf match {
+        case Term.Abst(_, _, p) => boxes(context, p)
+        case Term.AbsP(_, _, p) => boxes(context, p)
+        case Term.Appt(p, _) => boxes(context, p)
+        case Term.AppP(p, q) => boxes(context, p); boxes(context, q)
+        case thm: Term.PThm if !seen(thm.serial) =>
+          seen += thm.serial
+          val id = Thm_Id(thm.serial, thm.theory_name)
+          if (!suppress(id)) {
+            Export_Theory.read_proof(session_context, id, other_cache = other_cache) match {
+              case Some(p) =>
+                result += (thm.serial -> (id -> p))
+                boxes(Some((thm.serial, p.proof)), p.proof)
+              case None =>
+                error("Missing proof " + thm.serial + " (theory " + quote (thm.theory_name) + ")" +
+                  (context match {
+                    case None => ""
+                    case Some((i, p)) => " in proof " + i + ":\n" + p
+                  }))
+            }
+          }
+        case _ =>
+      }
+    }
+
+    boxes(None, proof)
+    result.iterator.map(_._2).toList
+  }
+
+
+  /* type classes */
+
+  sealed case class Class(params: List[(String, Term.Typ)], axioms: List[Prop])
+  extends Content[Class] {
+    override def cache(cache: Term.Cache): Class =
+      Class(
+        params.map({ case (name, typ) => (cache.string(name), cache.typ(typ)) }),
+        axioms.map(_.cache(cache)))
+  }
+
+  def read_classes(theory_context: Export.Theory_Context): List[Entity[Class]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "classes", Markup.CLASS,
+      { body =>
+        import XML.Decode._
+        import Term_XML.Decode._
+        val (params, axioms) = pair(list(pair(string, typ)), list(decode_prop))(body)
+        Class(params, axioms)
+      })
+
+
+  /* locales */
+
+  sealed case class Locale(
+    typargs: List[(String, Term.Sort)],
+    args: List[((String, Term.Typ), Syntax)],
+    axioms: List[Prop]
+  ) extends Content[Locale] {
+    override def cache(cache: Term.Cache): Locale =
+      Locale(
+        typargs.map({ case (name, sort) => (cache.string(name), cache.sort(sort)) }),
+        args.map({ case ((name, typ), syntax) => ((cache.string(name), cache.typ(typ)), syntax) }),
+        axioms.map(_.cache(cache)))
+  }
+
+  def read_locales(theory_context: Export.Theory_Context): List[Entity[Locale]] =
+    read_entities(theory_context, Export.THEORY_PREFIX + "locales", Markup.LOCALE,
+      { body =>
+        import XML.Decode._
+        import Term_XML.Decode._
+        val (typargs, args, axioms) =
+          triple(list(pair(string, sort)), list(pair(pair(string, typ), decode_syntax)),
+            list(decode_prop))(body)
+        Locale(typargs, args, axioms)
+      })
+
+
+  /* locale dependencies */
+
+  sealed case class Locale_Dependency(
+    source: String,
+    target: String,
+    prefix: List[(String, Boolean)],
+    subst_types: List[((String, Term.Sort), Term.Typ)],
+    subst_terms: List[((String, Term.Typ), Term.Term)]
+  ) extends Content[Locale_Dependency] {
+    override def cache(cache: Term.Cache): Locale_Dependency =
+      Locale_Dependency(
+        cache.string(source),
+        cache.string(target),
+        prefix.map({ case (name, mandatory) => (cache.string(name), mandatory) }),
+        subst_types.map({ case ((a, s), ty) => ((cache.string(a), cache.sort(s)), cache.typ(ty)) }),
+        subst_terms.map({ case ((x, ty), t) => ((cache.string(x), cache.typ(ty)), cache.term(t)) }))
+
+    def is_inclusion: Boolean =
+      subst_types.isEmpty && subst_terms.isEmpty
+  }
+
+  def read_locale_dependencies(
+    theory_context: Export.Theory_Context
+  ): List[Entity[Locale_Dependency]] = {
+    read_entities(theory_context, Export.THEORY_PREFIX + "locale_dependencies",
+      Kind.LOCALE_DEPENDENCY,
+      { body =>
+        import XML.Decode._
+        import Term_XML.Decode._
+        val (source, (target, (prefix, (subst_types, subst_terms)))) =
+          pair(string, pair(string, pair(list(pair(string, bool)),
+            pair(list(pair(pair(string, sort), typ)), list(pair(pair(string, typ), term))))))(body)
+        Locale_Dependency(source, target, prefix, subst_types, subst_terms)
+      })
+  }
+
+
+  /* sort algebra */
+
+  sealed case class Classrel(class1: String, class2: String, prop: Prop) {
+    def cache(cache: Term.Cache): Classrel =
+      Classrel(cache.string(class1), cache.string(class2), prop.cache(cache))
+  }
+
+  def read_classrel(theory_context: Export.Theory_Context): List[Classrel] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "classrel")
+    val classrel = {
+      import XML.Decode._
+      list(pair(decode_prop, pair(string, string)))(body)
+    }
+    for ((prop, (c1, c2)) <- classrel) yield Classrel(c1, c2, prop)
+  }
+
+  sealed case class Arity(
+    type_name: String,
+    domain: List[Term.Sort],
+    codomain: String,
+    prop: Prop
+  ) {
+    def cache(cache: Term.Cache): Arity =
+      Arity(cache.string(type_name), domain.map(cache.sort), cache.string(codomain),
+        prop.cache(cache))
+  }
+
+  def read_arities(theory_context: Export.Theory_Context): List[Arity] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "arities")
+    val arities = {
+      import XML.Decode._
+      import Term_XML.Decode._
+      list(pair(decode_prop, triple(string, list(sort), string)))(body)
+    }
+    for ((prop, (a, b, c)) <- arities) yield Arity(a, b, c, prop)
+  }
+
+
+  /* Pure constdefs */
+
+  sealed case class Constdef(name: String, axiom_name: String) {
+    def cache(cache: Term.Cache): Constdef =
+      Constdef(cache.string(name), cache.string(axiom_name))
+  }
+
+  def read_constdefs(theory_context: Export.Theory_Context): List[Constdef] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "constdefs")
+    val constdefs = {
+      import XML.Decode._
+      list(pair(string, string))(body)
+    }
+    for ((name, axiom_name) <- constdefs) yield Constdef(name, axiom_name)
+  }
+
+
+  /* HOL typedefs */
+
+  sealed case class Typedef(
+    name: String,
+    rep_type: Term.Typ,
+    abs_type: Term.Typ,
+    rep_name: String,
+    abs_name: String,
+    axiom_name: String
+  ) {
+    def cache(cache: Term.Cache): Typedef =
+      Typedef(cache.string(name),
+        cache.typ(rep_type),
+        cache.typ(abs_type),
+        cache.string(rep_name),
+        cache.string(abs_name),
+        cache.string(axiom_name))
+  }
+
+  def read_typedefs(theory_context: Export.Theory_Context): List[Typedef] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "typedefs")
+    val typedefs = {
+      import XML.Decode._
+      import Term_XML.Decode._
+      list(pair(string, pair(typ, pair(typ, pair(string, pair(string, string))))))(body)
+    }
+    for { (name, (rep_type, (abs_type, (rep_name, (abs_name, axiom_name))))) <- typedefs }
+    yield Typedef(name, rep_type, abs_type, rep_name, abs_name, axiom_name)
+  }
+
+
+  /* HOL datatypes */
+
+  sealed case class Datatype(
+    pos: Position.T,
+    name: String,
+    co: Boolean,
+    typargs: List[(String, Term.Sort)],
+    typ: Term.Typ,
+    constructors: List[(Term.Term, Term.Typ)]
+  ) {
+    def id: Option[Long] = Position.Id.unapply(pos)
+
+    def cache(cache: Term.Cache): Datatype =
+      Datatype(
+        cache.position(pos),
+        cache.string(name),
+        co,
+        typargs.map({ case (name, sort) => (cache.string(name), cache.sort(sort)) }),
+        cache.typ(typ),
+        constructors.map({ case (term, typ) => (cache.term(term), cache.typ(typ)) }))
+  }
+
+  def read_datatypes(theory_context: Export.Theory_Context): List[Datatype] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "datatypes")
+    val datatypes = {
+      import XML.Decode._
+      import Term_XML.Decode._
+      list(pair(properties, pair(string, pair(bool, pair(list(pair(string, sort)),
+            pair(typ, list(pair(term, typ))))))))(body)
+    }
+    for ((pos, (name, (co, (typargs, (typ, constructors))))) <- datatypes)
+      yield Datatype(pos, name, co, typargs, typ, constructors)
+  }
+
+
+  /* Pure spec rules */
+
+  sealed abstract class Recursion {
+    def cache(cache: Term.Cache): Recursion =
+      this match {
+        case Primrec(types) => Primrec(types.map(cache.string))
+        case Primcorec(types) => Primcorec(types.map(cache.string))
+        case _ => this
+      }
+  }
+  case class Primrec(types: List[String]) extends Recursion
+  case object Recdef extends Recursion
+  case class Primcorec(types: List[String]) extends Recursion
+  case object Corec extends Recursion
+  case object Unknown_Recursion extends Recursion
+
+  val decode_recursion: XML.Decode.T[Recursion] = {
+    import XML.Decode._
+    variant(List(
+      { case (Nil, a) => Primrec(list(string)(a)) },
+      { case (Nil, Nil) => Recdef },
+      { case (Nil, a) => Primcorec(list(string)(a)) },
+      { case (Nil, Nil) => Corec },
+      { case (Nil, Nil) => Unknown_Recursion }))
+  }
+
+
+  sealed abstract class Rough_Classification {
+    def is_equational: Boolean = this.isInstanceOf[Equational]
+    def is_inductive: Boolean = this == Inductive
+    def is_co_inductive: Boolean = this == Co_Inductive
+    def is_relational: Boolean = is_inductive || is_co_inductive
+    def is_unknown: Boolean = this == Unknown
+
+    def cache(cache: Term.Cache): Rough_Classification =
+      this match {
+        case Equational(recursion) => Equational(recursion.cache(cache))
+        case _ => this
+      }
+  }
+  case class Equational(recursion: Recursion) extends Rough_Classification
+  case object Inductive extends Rough_Classification
+  case object Co_Inductive extends Rough_Classification
+  case object Unknown extends Rough_Classification
+
+  val decode_rough_classification: XML.Decode.T[Rough_Classification] = {
+    import XML.Decode._
+    variant(List(
+      { case (Nil, a) => Equational(decode_recursion(a)) },
+      { case (Nil, Nil) => Inductive },
+      { case (Nil, Nil) => Co_Inductive },
+      { case (Nil, Nil) => Unknown }))
+  }
+
+
+  sealed case class Spec_Rule(
+    pos: Position.T,
+    name: String,
+    rough_classification: Rough_Classification,
+    typargs: List[(String, Term.Sort)],
+    args: List[(String, Term.Typ)],
+    terms: List[(Term.Term, Term.Typ)],
+    rules: List[Term.Term]
+  ) {
+    def id: Option[Long] = Position.Id.unapply(pos)
+
+    def cache(cache: Term.Cache): Spec_Rule =
+      Spec_Rule(
+        cache.position(pos),
+        cache.string(name),
+        rough_classification.cache(cache),
+        typargs.map({ case (name, sort) => (cache.string(name), cache.sort(sort)) }),
+        args.map({ case (name, typ) => (cache.string(name), cache.typ(typ)) }),
+        terms.map({ case (term, typ) => (cache.term(term), cache.typ(typ)) }),
+        rules.map(cache.term))
+  }
+
+  def read_spec_rules(theory_context: Export.Theory_Context): List[Spec_Rule] = {
+    val body = theory_context.yxml(Export.THEORY_PREFIX + "spec_rules")
+    val spec_rules = {
+      import XML.Decode._
+      import Term_XML.Decode._
+      list(
+        pair(properties, pair(string, pair(decode_rough_classification,
+          pair(list(pair(string, sort)), pair(list(pair(string, typ)),
+            pair(list(pair(term, typ)), list(term))))))))(body)
+    }
+    for ((pos, (name, (rough_classification, (typargs, (args, (terms, rules)))))) <- spec_rules)
+      yield Spec_Rule(pos, name, rough_classification, typargs, args, terms, rules)
+  }
+
+
+  /* other entities */
+
+  sealed case class Other() extends Content[Other] {
+    override def cache(cache: Term.Cache): Other = this
+  }
+
+  def read_others(theory_context: Export.Theory_Context): Map[String, List[Entity[Other]]] = {
+    val kinds =
+      theory_context.get(Export.THEORY_PREFIX + "other_kinds") match {
+        case Some(entry) => split_lines(entry.text)
+        case None => Nil
+      }
+    val other = Other()
+    def read_other(kind: String): List[Entity[Other]] =
+      read_entities(theory_context, Export.THEORY_PREFIX + "other/" + kind, kind, _ => other)
+
+    kinds.map(kind => kind -> read_other(kind)).toMap
+  }
+}