diff --git a/src/Pure/Thy/export_theory.ML b/src/Pure/Thy/export_theory.ML
--- a/src/Pure/Thy/export_theory.ML
+++ b/src/Pure/Thy/export_theory.ML
@@ -1,491 +1,481 @@
 (*  Title:      Pure/Thy/export_theory.ML
     Author:     Makarius
 
 Export foundational theory content and locale/class structure.
 *)
 
 signature EXPORT_THEORY =
 sig
   val other_name_space: (theory -> Name_Space.T) -> theory -> theory
   val export_enabled: Thy_Info.presentation_context -> bool
   val export_body: theory -> string -> XML.body -> unit
 end;
 
 structure Export_Theory: EXPORT_THEORY =
 struct
 
 (* other name spaces *)
 
 fun err_dup_kind kind = error ("Duplicate name space kind " ^ quote kind);
 
 structure Data = Theory_Data
 (
-  type T = ((theory -> Name_Space.T) * serial) Symtab.table;
-  val empty = Symtab.empty;
+  type T = (theory -> Name_Space.T) Inttab.table;
+  val empty = Inttab.empty;
   val extend = I;
-  fun merge data =
-    Symtab.merge (eq_snd op =) data
-      handle Symtab.DUP dup => err_dup_kind dup;
+  val merge = Inttab.merge (K true);
 );
 
-val other_name_spaces = map (#1 o #2) o Symtab.dest o Data.get;
-
-fun other_name_space get_space thy =
-  let
-    val kind = Name_Space.kind_of (get_space thy);
-    val entry = (get_space, serial ());
-  in
-    Data.map (Symtab.update_new (kind, entry)) thy
-      handle Symtab.DUP dup => err_dup_kind dup
-  end;
+val other_name_spaces = map #2 o Inttab.dest o Data.get;
+fun other_name_space get_space thy = Data.map (Inttab.update (serial (), get_space)) thy;
 
 val _ = Theory.setup
  (other_name_space Thm.oracle_space #>
   other_name_space Global_Theory.fact_space #>
   other_name_space (Bundle.bundle_space o Context.Theory) #>
   other_name_space (Attrib.attribute_space o Context.Theory) #>
   other_name_space (Method.method_space o Context.Theory));
 
 
 (* approximative syntax *)
 
 val get_syntax = Syntax.get_approx o Proof_Context.syn_of;
 fun get_syntax_type ctxt = get_syntax ctxt o Lexicon.mark_type;
 fun get_syntax_const ctxt = get_syntax ctxt o Lexicon.mark_const;
 fun get_syntax_fixed ctxt = get_syntax ctxt o Lexicon.mark_fixed;
 
 fun get_syntax_param ctxt loc x =
   let val thy = Proof_Context.theory_of ctxt in
     if Class.is_class thy loc then
       (case AList.lookup (op =) (Class.these_params thy [loc]) x of
         NONE => NONE
       | SOME (_, (c, _)) => get_syntax_const ctxt c)
     else get_syntax_fixed ctxt x
   end;
 
 val encode_syntax =
   XML.Encode.variant
    [fn NONE => ([], []),
     fn SOME (Syntax.Prefix delim) => ([delim], []),
     fn SOME (Syntax.Infix {assoc, delim, pri}) =>
       let
         val ass =
           (case assoc of
             Printer.No_Assoc => 0
           | Printer.Left_Assoc => 1
           | Printer.Right_Assoc => 2);
         open XML.Encode Term_XML.Encode;
       in ([], triple int string int (ass, delim, pri)) end];
 
 
 (* free variables: not declared in the context *)
 
 val is_free = not oo Name.is_declared;
 
 fun add_frees used =
   fold_aterms (fn Free (x, T) => is_free used x ? insert (op =) (x, T) | _ => I);
 
 fun add_tfrees used =
   (fold_types o fold_atyps) (fn TFree (a, S) => is_free used a ? insert (op =) (a, S) | _ => I);
 
 
 (* locales *)
 
 fun locale_content thy loc =
   let
     val ctxt = Locale.init loc thy;
     val args =
       Locale.params_of thy loc
       |> map (fn ((x, T), _) => ((x, T), get_syntax_param ctxt loc x));
     val axioms =
       let
         val (asm, defs) = Locale.specification_of thy loc;
         val cprops = map (Thm.cterm_of ctxt) (the_list asm @ defs);
         val (intro1, intro2) = Locale.intros_of thy loc;
         val intros_tac = Method.try_intros_tac ctxt (the_list intro1 @ the_list intro2) [];
         val res =
           Goal.init (Conjunction.mk_conjunction_balanced cprops)
           |> (ALLGOALS Goal.conjunction_tac THEN intros_tac)
           |> try Seq.hd;
       in
         (case res of
           SOME goal => Thm.prems_of goal
         | NONE => raise Fail ("Cannot unfold locale " ^ quote loc))
       end;
     val typargs = build_rev (fold Term.add_tfrees (map (Free o #1) args @ axioms));
   in {typargs = typargs, args = args, axioms = axioms} end;
 
 fun get_locales thy =
   Locale.get_locales thy |> map_filter (fn loc =>
     if Experiment.is_experiment thy loc then NONE else SOME (loc, ()));
 
 fun get_dependencies prev_thys thy =
   Locale.dest_dependencies prev_thys thy |> map_filter (fn dep =>
     if Experiment.is_experiment thy (#source dep) orelse
       Experiment.is_experiment thy (#target dep) then NONE
     else
       let
         val (type_params, params) = Locale.parameters_of thy (#source dep);
         val typargs = fold (Term.add_tfreesT o #2 o #1) params type_params;
         val substT =
           typargs |> map_filter (fn v =>
             let
               val T = TFree v;
               val T' = Morphism.typ (#morphism dep) T;
             in if T = T' then NONE else SOME (v, T') end);
         val subst =
           params |> map_filter (fn (v, _) =>
             let
               val t = Free v;
               val t' = Morphism.term (#morphism dep) t;
             in if t aconv t' then NONE else SOME (v, t') end);
       in SOME (dep, (substT, subst)) end);
 
 
 (* presentation *)
 
 fun export_enabled (context: Thy_Info.presentation_context) =
   Options.bool (#options context) "export_theory";
 
 fun export_body thy name body =
   if XML.is_empty_body body then ()
   else Export.export thy (Path.binding0 (Path.make ("theory" :: space_explode "/" name))) body;
 
 val _ = (Theory.setup o Thy_Info.add_presentation) (fn context => fn thy =>
   let
     val rep_tsig = Type.rep_tsig (Sign.tsig_of thy);
     val consts = Sign.consts_of thy;
     val thy_ctxt = Proof_Context.init_global thy;
 
     val pos_properties = Thy_Info.adjust_pos_properties context;
 
     val enabled = export_enabled context;
 
 
     (* strict parents *)
 
     val parents = Theory.parents_of thy;
     val _ =
       Export.export thy \<^path_binding>\<open>theory/parents\<close>
         (XML.Encode.string (cat_lines (map Context.theory_long_name parents)));
 
 
     (* spec rules *)
 
     fun spec_rule_content {pos, name, rough_classification, terms, rules} =
       let
         val spec =
           terms @ map Thm.plain_prop_of rules
           |> Term_Subst.zero_var_indexes_list
           |> map Logic.unvarify_global;
       in
        {props = pos_properties pos,
         name = name,
         rough_classification = rough_classification,
         typargs = build_rev (fold Term.add_tfrees spec),
         args = build_rev (fold Term.add_frees spec),
         terms = map (fn t => (t, Term.type_of t)) (take (length terms) spec),
         rules = drop (length terms) spec}
       end;
 
 
     (* entities *)
 
     fun make_entity_markup name xname pos serial =
       let val props = pos_properties pos @ Markup.serial_properties serial;
       in (Markup.entityN, (Markup.nameN, name) :: (Markup.xnameN, xname) :: props) end;
 
     fun entity_markup space name =
       let
         val xname = Name_Space.extern_shortest thy_ctxt space name;
         val {serial, pos, ...} = Name_Space.the_entry space name;
       in make_entity_markup name xname pos serial end;
 
     fun export_entities export_name get_space decls export =
       let
         val parent_spaces = map get_space parents;
         val space = get_space thy;
       in
         build (decls |> fold (fn (name, decl) =>
           if exists (fn space => Name_Space.declared space name) parent_spaces then I
           else
             (case export name decl of
               NONE => I
             | SOME make_body =>
                 let
                   val i = #serial (Name_Space.the_entry space name);
                   val body = if enabled then make_body () else [];
                 in cons (i, XML.Elem (entity_markup space name, body)) end)))
         |> sort (int_ord o apply2 #1) |> map #2
         |> export_body thy export_name
       end;
 
 
     (* types *)
 
     val encode_type =
       let open XML.Encode Term_XML.Encode
       in triple encode_syntax (list string) (option typ) end;
 
     val _ =
       export_entities "types" Sign.type_space (Name_Space.dest_table (#types rep_tsig))
         (fn c =>
           (fn Type.LogicalType n =>
                 SOME (fn () =>
                   encode_type (get_syntax_type thy_ctxt c, Name.invent Name.context Name.aT n, NONE))
             | Type.Abbreviation (args, U, false) =>
                 SOME (fn () =>
                   encode_type (get_syntax_type thy_ctxt c, args, SOME U))
             | _ => NONE));
 
 
     (* consts *)
 
     val encode_term = Term_XML.Encode.term consts;
 
     val encode_const =
       let open XML.Encode Term_XML.Encode
       in pair encode_syntax (pair (list string) (pair typ (pair (option encode_term) bool))) end;
 
     val _ =
       export_entities "consts" Sign.const_space (#constants (Consts.dest consts))
         (fn c => fn (T, abbrev) =>
           SOME (fn () =>
             let
               val syntax = get_syntax_const thy_ctxt c;
               val U = Logic.unvarifyT_global T;
               val U0 = Type.strip_sorts U;
               val trim_abbrev =
                 Proofterm.standard_vars_term Name.context #> map_types Type.strip_sorts;
               val abbrev' = Option.map trim_abbrev abbrev;
               val args = map (#1 o dest_TFree) (Consts.typargs consts (c, U0));
               val propositional = Object_Logic.is_propositional thy_ctxt (Term.body_type U0);
             in encode_const (syntax, (args, (U0, (abbrev', propositional)))) end));
 
 
     (* axioms *)
 
     fun standard_prop used extra_shyps raw_prop raw_proof =
       let
         val (prop, proof) = Proofterm.standard_vars used (raw_prop, raw_proof);
         val args = rev (add_frees used prop []);
         val typargs = rev (add_tfrees used prop []);
         val used_typargs = fold (Name.declare o #1) typargs used;
         val sorts = Name.invent used_typargs Name.aT (length extra_shyps) ~~ extra_shyps;
       in ((sorts @ typargs, args, prop), proof) end;
 
     fun standard_prop_of thm =
       standard_prop Name.context (Thm.extra_shyps thm) (Thm.full_prop_of thm);
 
     val encode_prop =
       let open XML.Encode Term_XML.Encode
       in triple (list (pair string sort)) (list (pair string typ)) encode_term end;
 
     fun encode_axiom used prop =
       encode_prop (#1 (standard_prop used [] prop NONE));
 
     val _ =
       export_entities "axioms" Theory.axiom_space (Theory.all_axioms_of thy)
         (fn _ => fn prop => SOME (fn () => encode_axiom Name.context prop));
 
 
     (* theorems and proof terms *)
 
     val clean_thm = Thm.check_hyps (Context.Theory thy) #> Thm.strip_shyps;
     val prep_thm = clean_thm #> Thm.unconstrainT #> Thm.strip_shyps;
 
     val lookup_thm_id = Global_Theory.lookup_thm_id thy;
 
     fun expand_name thm_id (header: Proofterm.thm_header) =
       if #serial header = #serial thm_id then ""
       else
         (case lookup_thm_id (Proofterm.thm_header_id header) of
           NONE => ""
         | SOME thm_name => Thm_Name.print thm_name);
 
     fun entity_markup_thm (serial, (name, i)) =
       let
         val space = Global_Theory.fact_space thy;
         val xname = Name_Space.extern_shortest thy_ctxt space name;
         val {pos, ...} = Name_Space.the_entry space name;
       in make_entity_markup (Thm_Name.print (name, i)) (Thm_Name.print (xname, i)) pos serial end;
 
     fun encode_thm thm_id raw_thm =
       let
         val deps = map (Thm_Name.print o #2) (Thm_Deps.thm_deps thy [raw_thm]);
         val thm = prep_thm raw_thm;
 
         val proof0 =
           if Proofterm.export_standard_enabled () then
             Proof_Syntax.standard_proof_of
               {full = true, expand_name = SOME o expand_name thm_id} thm
           else if Proofterm.export_enabled () then Thm.reconstruct_proof_of thm
           else MinProof;
         val (prop, SOME proof) = standard_prop_of thm (SOME proof0);
         val _ = Thm.expose_proofs thy [thm];
       in
         (prop, deps, proof) |>
           let
             open XML.Encode Term_XML.Encode;
             val encode_proof = Proofterm.encode_standard_proof consts;
           in triple encode_prop (list string) encode_proof end
       end;
 
     fun export_thm (thm_id, thm_name) =
       let
         val markup = entity_markup_thm (#serial thm_id, thm_name);
         val body =
           if enabled then
             Global_Theory.get_thm_name thy (thm_name, Position.none)
             |> encode_thm thm_id
           else [];
       in XML.Elem (markup, body) end;
 
     val _ = export_body thy "thms" (map export_thm (Global_Theory.dest_thm_names thy));
 
 
     (* type classes *)
 
     val encode_class =
       let open XML.Encode Term_XML.Encode
       in pair (list (pair string typ)) (list (encode_axiom Name.context)) end;
 
     val _ =
       export_entities "classes" Sign.class_space
         (map (rpair ()) (Graph.keys (Sorts.classes_of (#2 (#classes rep_tsig)))))
         (fn name => fn () => SOME (fn () =>
           (case try (Axclass.get_info thy) name of
             NONE => ([], [])
           | SOME {params, axioms, ...} => (params, map (Thm.plain_prop_of o clean_thm) axioms))
           |> encode_class));
 
 
     (* sort algebra *)
 
     val _ =
       if enabled then
         let
           val prop = encode_axiom Name.context o Logic.varify_global;
 
           val encode_classrel =
             let open XML.Encode
             in list (pair prop (pair string string)) end;
 
           val encode_arities =
             let open XML.Encode Term_XML.Encode
             in list (pair prop (triple string (list sort) string)) end;
 
           val export_classrel =
             maps (fn (c, cs) => map (pair c) cs) #> map (`Logic.mk_classrel) #> encode_classrel;
 
           val export_arities = map (`Logic.mk_arity) #> encode_arities;
 
           val {classrel, arities} =
             Sorts.dest_algebra (map (#2 o #classes o Type.rep_tsig o Sign.tsig_of) parents)
               (#2 (#classes rep_tsig));
         in
           if null classrel then () else export_body thy "classrel" (export_classrel classrel);
           if null arities then () else export_body thy "arities" (export_arities arities)
         end
       else ();
 
 
     (* locales *)
 
     fun encode_locale used =
       let open XML.Encode Term_XML.Encode in
         triple (list (pair string sort)) (list (pair (pair string typ) encode_syntax))
           (list (encode_axiom used))
       end;
 
     val _ =
       export_entities "locales" Locale.locale_space (get_locales thy)
         (fn loc => fn () => SOME (fn () =>
           let
             val {typargs, args, axioms} = locale_content thy loc;
             val used = fold Name.declare (map #1 typargs @ map (#1 o #1) args) Name.context;
           in encode_locale used (typargs, args, axioms) end
           handle ERROR msg =>
             cat_error msg ("The error(s) above occurred in locale " ^
               quote (Locale.markup_name thy_ctxt loc))));
 
 
     (* locale dependencies *)
 
     fun encode_locale_dependency (dep: Locale.locale_dependency, subst) =
       (#source dep, (#target dep, (#prefix dep, subst))) |>
         let
           open XML.Encode Term_XML.Encode;
           val encode_subst =
             pair (list (pair (pair string sort) typ)) (list (pair (pair string typ) (term consts)));
         in pair string (pair string (pair (list (pair string bool)) encode_subst)) end;
 
     val _ =
       if enabled then
         get_dependencies parents thy |> map_index (fn (i, dep) =>
           let
             val xname = string_of_int (i + 1);
             val name = Long_Name.implode [Context.theory_name thy, xname];
             val markup = make_entity_markup name xname (#pos (#1 dep)) (#serial (#1 dep));
             val body = encode_locale_dependency dep;
           in XML.Elem (markup, body) end)
         |> export_body thy "locale_dependencies"
       else ();
 
 
     (* constdefs *)
 
     val _ =
       if enabled then
         let
           val constdefs =
             Defs.dest_constdefs (map Theory.defs_of (Theory.parents_of thy)) (Theory.defs_of thy)
             |> sort_by #1;
           val encode =
             let open XML.Encode
             in list (pair string string) end;
         in if null constdefs then () else export_body thy "constdefs" (encode constdefs) end
       else ();
 
 
     (* spec rules *)
 
     val encode_specs =
       let open XML.Encode Term_XML.Encode in
         list (fn {props, name, rough_classification, typargs, args, terms, rules} =>
           pair properties (pair string (pair Spec_Rules.encode_rough_classification
             (pair (list (pair string sort)) (pair (list (pair string typ))
               (pair (list (pair encode_term typ)) (list encode_term))))))
               (props, (name, (rough_classification, (typargs, (args, (terms, rules)))))))
       end;
 
     val _ =
       if enabled then
         (case Spec_Rules.dest_theory thy of
           [] => ()
         | spec_rules =>
             export_body thy "spec_rules" (encode_specs (map spec_rule_content spec_rules)))
       else ();
 
 
     (* other entities *)
 
     fun export_other get_space =
       let
         val space = get_space thy;
         val export_name = "other/" ^ Name_Space.kind_of space;
         val decls = Name_Space.get_names space |> map (rpair ());
       in export_entities export_name get_space decls (fn _ => fn () => SOME (K [])) end;
 
     val other_spaces = other_name_spaces thy;
     val other_kinds = map (fn get_space => Name_Space.kind_of (get_space thy)) other_spaces;
     val _ =
       if null other_kinds then ()
       else
         Export.export thy \<^path_binding>\<open>theory/other_kinds\<close>
           (XML.Encode.string (cat_lines other_kinds));
     val _ = List.app export_other other_spaces;
 
   in () end);
 
 end;