diff --git a/src/gmser_dyn.erl b/src/gmser_dyn.erl
index 78a0c82..8bb0930 100644
--- a/src/gmser_dyn.erl
+++ b/src/gmser_dyn.erl
@@ -1,11 +1,17 @@
 -module(gmser_dyn).
 
--export([ encode/1
-        , encode/2
-        , encode_typed/2
-        , encode_typed/3
-        , decode/1
-        , decode/2 ]).
+-export([ encode/1           %% (Term)                   -> rlp()
+        , encode/2           %% (Term, Types)            -> rlp()
+        , encode/3           %% (Term, Vsn, Types)       -> rlp()
+        , encode_typed/2     %% (Type, Term)             -> rlp()
+        , encode_typed/3     %% (Type, Term, Types)      -> rlp()
+        , encode_typed/4     %% (Type, Term, Vsn, Types) -> rlp()
+        , decode/1           %% (RLP)                    -> Term
+        , decode/2           %% (RLP, Types)             -> Term
+        , decode/3           %% (RLP, Vsn, Types)        -> Term
+        , decode_typed/2     %% (Type, RLP)              -> Term
+        , decode_typed/3     %% (Type, RLP, Types)       -> Term
+        , decode_typed/4 ]). %% (Type, RLP, Vsn, Types)  -> Term
 
 -export([ serialize/1
         , serialize/2
@@ -17,6 +23,7 @@
 %% register a type schema, inspect existing schema
 -export([ register_types/1
         , registered_types/0
+        , latest_vsn/0
         , get_opts/1
         , set_opts/1
         , set_opts/2
@@ -26,7 +33,8 @@
 
 %% Register individual types, or cache labels
 -export([ register_type/3
-        , cache_label/2 ]).
+        , cache_label/2
+        ]).
 
 -import(gmserialization, [ decode_field/2 ]).
 
@@ -39,46 +47,112 @@
 -include_lib("eunit/include/eunit.hrl").
 -endif.
 
-serialize(Term)                    -> rlp_encode(encode(Term)).
-serialize(Term, Types)             -> rlp_encode(encode(Term, Types)).
-serialize_typed(Type, Term)        -> rlp_encode(encode_typed(Type, Term)).
-serialize_typed(Type, Term, Types) -> rlp_encode(encode_typed(Type, Term, Types)).
+serialize(Term) ->
+    Vsn = latest_vsn(),
+    rlp_encode(encode_(Term, Vsn, registered_types(Vsn))).
 
-deserialize(Binary) -> decode(rlp_decode(Binary)).
-deserialize(Binary, Types) -> decode(rlp_decode(Binary), Types).
+serialize(Term, Types) ->
+    Vsn = types_vsn(Types),
+    rlp_encode(encode_(Term, Vsn, Types)).
 
+serialize(Term, Vsn, Types) ->
+    rlp_encode(encode_(Term, Vsn, Types)).
+
+serialize_typed(Type, Term) ->
+    Vsn = latest_vsn(),
+    rlp_encode(encode_typed_(Type, Term, Vsn, registered_types(Vsn))).
+
+serialize_typed(Type, Term, Types) ->
+    Vsn = types_vsn(Types),
+    rlp_encode(encode_typed_(Type, Term, Vsn, Types)).
+
+serialize_typed(Type, Term, Vsn, Types) ->
+    rlp_encode(encode_typed_(Type, Term, Vsn, Types)).
+
+deserialize(Binary) ->
+    Fields0 = rlp_decode(Binary),
+    case decode_tag_and_vsn(Fields0) of
+        {0, Vsn, Fields} ->
+            decode(Fields, Vsn, registered_types(Vsn));
+        Other ->
+            error({illegal_serialization, Other})
+    end.
+
+deserialize(Binary, Types) ->
+    Vsn0 = maps:get(vsn, Types, undefined),
+    Fields0 = rlp_decode(Binary),
+    case decode_tag_and_vsn(Fields0) of
+        {0, Vsn, Fields} when Vsn0 == undefined; Vsn0 == Vsn ->
+            decode(Fields, Vsn, Types);
+        Other ->
+            error({illegal_serialization, Other})
+    end.
+            
+deserialize(Binary, Vsn, Types) ->
+    Fields0 = rlp_decode(Binary),
+    case decode_tag_and_vsn(Fields0) of
+        {0, Vsn, Fields} ->
+            decode(Fields, Vsn, Types);
+        Other ->
+            error({illegal_serialization, Other})
+    end.
 
 encode(Term) ->
-    encode(Term, registered_types()).
+    Vsn = latest_vsn(),
+    encode(Term, Vsn, registered_types(Vsn)).
 
 encode(Term, Types) ->
-    encode(Term, vsn(Types), Types).
+    encode(Term, types_vsn(Types), Types).
 
-encode(Term, Vsn, Types) ->
+encode(Term, Vsn, Types0) ->
+    Types = assert_vsn(Vsn, Types0),
     [ encode_basic(int, 0)
     , encode_basic(int, Vsn)
     , encode_(Term, Vsn, Types) ].
 
 encode_typed(Type, Term) ->
-    encode_typed(Type, Term, registered_types()).
+    Vsn = latest_vsn(),
+    encode_typed(Type, Term, Vsn, registered_types(Vsn)).
 
 encode_typed(Type, Term, Types) ->
-    encode_typed(Type, Term, vsn(Types), Types).
+    encode_typed(Type, Term, types_vsn(Types), Types).
 
-encode_typed(Type, Term, Vsn, Types) ->
+encode_typed(Type, Term, Vsn, Types0) ->
+    Types = assert_vsn(Vsn, Types0),
     [ encode_basic(int, 0)
     , encode_basic(int, Vsn)
     , encode_typed_(Type, Term, Vsn, Types) ].
 
 decode(Fields) ->
-    decode(Fields, registered_types()).
+    Vsn = latest_vsn(),
+    decode(Fields, Vsn, registered_types(Vsn)).
 
-decode(Fields0, Types) ->
+decode(Fields, Types) ->
+    decode(Fields, types_vsn(Types), Types).
+
+decode(Fields0, Vsn, Types0) ->
+    Types = assert_vsn(Vsn, Types0),
     case decode_tag_and_vsn(Fields0) of
         {0, Vsn, Fields} ->
             decode_(Fields, Vsn, Types);
         Other ->
-            error({illegal_serialization, Other})
+            error({illegal_encoding, Other})
+    end.
+
+decode_typed(Type, Fields) ->
+    Vsn = latest_vsn(),
+    decode_typed(Type, Fields, Vsn, registered_types(Vsn)).
+
+decode_typed(Type, Fields, Types) ->
+    decode_typed(Type, Fields, types_vsn(Types), Types).
+
+decode_typed(Type, Fields0, Vsn, Types0) ->
+    Types = assert_vsn(Vsn, Types0),
+    case decode_tag_and_vsn(Fields0) of
+        {0, Vsn, Fields} ->
+            decode_from_template(Type, Fields, Vsn, Types);
+        Other ->
+            error({illegal_encoding, Other})
     end.
 
 decode_tag_and_vsn([TagBin, VsnBin, Fields]) ->
@@ -86,6 +160,13 @@ decode_tag_and_vsn([TagBin, VsnBin, Fields]) ->
      decode_basic(int, VsnBin),
      Fields}.
 
+types_vsn(#{vsn := Vsn}) -> Vsn;
+types_vsn(_) -> latest_vsn().
+
+assert_vsn(V, #{vsn := V} = Types) -> Types;
+assert_vsn(V, #{vsn := Other}    ) -> error({version_mismatch, V, Other});
+assert_vsn(V, #{} = Types        ) -> Types#{vsn => V}.
+
 dynamic_types() ->
     #{ vsn   => ?VSN
      , codes =>
@@ -127,15 +208,17 @@ dynamic_types() ->
      , options => #{}
        }.
 
-vsn(Types) ->
-    maps:get(vsn, Types, ?VSN).
-
 registered_types() ->
-    case persistent_term:get({?MODULE, types}, undefined) of
+    registered_types(latest_vsn()).
+
+registered_types(Vsn) ->
+    case persistent_term:get(pt_key(), undefined) of
         undefined ->
             dynamic_types();
-        Types when is_map(Types) ->
-            Types
+        #{latest_vsn := _, types := #{Vsn := Types}} ->
+            Types;
+        #{latest_vsn := _, types := _} ->
+            dynamic_types()
     end.
 
 template(TagOrCode, Vsn, Types) ->
@@ -213,6 +296,8 @@ encode_maybe_template(#{items := _} = Type, Term, Vsn, Types) ->
     end;
 encode_maybe_template(#{alt := _} = Type, Term, Vsn, Types) ->
     encode_from_template(Type, Term, Vsn, emit(dyn()), Types);
+encode_maybe_template(#{switch := _} = Type, Term, Vsn, Types) ->
+    encode_from_template(Type, Term, Vsn, emit(dyn()), Types);
 encode_maybe_template(Pat, Term, Vsn, Types) when is_list(Pat);
                                                   is_tuple(Pat) ->
     encode_from_template(Pat, Term, emit(dyn()), Vsn, Types);
@@ -249,14 +334,19 @@ auto_template(T) ->
 decode_from_template(any, Fld, Vsn, Types) ->
     decode_(Fld, Vsn, Types);
 decode_from_template(#{items := Items}, Fld, Vsn, Types) when is_list(Fld) ->
-    Zipped = lists:zip(Items, Fld),
+    Zipped = lists:zipwith(
+               fun({{K, T}, V}) -> {K, T, V};
+                  ({{opt,K,T}, V}) -> {K, T, V}
+               end, Items, Fld),
     lists:foldl(
-      fun({{K, Type}, V}, Map) ->
+      fun({K, Type, V}, Map) ->
               maps:is_key(K, Map) andalso error(badarg, duplicate_field),
               Map#{K => decode_from_template({any,Type}, V, Vsn, Types)}
       end, #{}, Zipped);
 decode_from_template(#{alt := Alts} = T, Fld, Vsn, Types) when is_list(Alts) ->
     decode_alt(Alts, Fld, T, Vsn, Types);
+decode_from_template(#{switch := Alts} = T, Fld, Vsn, Types) when is_map(Alts) ->
+    decode_switch(Alts, Fld, T, Vsn, Types);
 decode_from_template(list, Flds, Vsn, Types) ->
     [decode_(F, Vsn, Types) || F <- Flds];
 decode_from_template(map, Fld, Vsn, Types) ->
@@ -296,15 +386,28 @@ encode_from_template(list, L, E, Vsn, Types) when is_list(L) ->
 encode_from_template(#{items := Items}, M, E, Vsn, Types) ->
     assert_type(is_map(M), map, M),
     Emit = noemit(E),
+    Encode = fun(K, Type, V) ->
+                     [encode_from_template(any, K, Emit, Vsn, Types),
+                      encode_from_template(Type, V, Emit, Vsn, Types)]
+             end,
     emit(E, map, Types,
-         lists:map(
-           fun({K, Type}) ->
+         lists:foldr(
+           fun({K, Type}, Acc) ->
                    V = maps:get(K, M),
-                   [encode_from_template(any, K, Emit, Vsn, Types),
-                    encode_from_template(Type, V, Emit, Vsn, Types)]
-           end, Items));
+                   [Encode(K, Type, V) | Acc];
+              ({opt, K, Type}, Acc) ->
+                   case maps:find(K, M) of
+                       {ok, V} ->
+                           [Encode(K, Type, V) | Acc];
+                       error ->
+                           Acc
+                   end
+           end, [], Items));
 encode_from_template(#{alt := Alts} = T, Term, E, Vsn, Types) when is_list(Alts) ->
     encode_alt(Alts, Term, T, E, Vsn, Types);
+encode_from_template(#{switch := Alts} = T, Term, E, Vsn, Types) when is_map(Alts),
+                                                                      is_map(Term) ->
+    encode_switch(Alts, Term, T, E, Vsn, Types);
 encode_from_template(map, M, E, Vsn, Types) ->
     assert_type(is_map(M), map, M),
     Emit = emit(E),
@@ -370,6 +473,30 @@ encode_alt_([A|Alts], Term, T, E, Vsn, Types) ->
 encode_alt_([], Term, T, _, _, _) ->
     error({illegal, T, Term}).
 
+decode_switch(Alts, Fld, T, Vsn, Types) ->
+    [KFld, VFld] = Fld,
+    Key = decode_(KFld, Vsn, Types),
+    case maps:find(Key, Alts) of
+        {ok, SubType} ->
+            SubTerm = decode_from_template(SubType, VFld, Vsn, Types),
+            #{Key => SubTerm};
+        error ->
+            error({illegal, T, Fld})
+    end.
+
+encode_switch(Alts, Term, T, E, Vsn, Types) ->
+    assert_type(map_size(Term) == 1, singleton_map, Term),
+    [{Key, Subterm}] = maps:to_list(Term),
+    case maps:find(Key, Alts) of
+        {ok, SubType} ->
+            Enc = encode_from_template(SubType, Subterm, E, Vsn, Types),
+            emit(E, map, Types,
+                 [[encode_from_template(any, Key, E, Vsn, Types),
+                   Enc]]);
+        error ->
+            error({illegal, T, Term})
+    end.
+
 %% Basically, dynamically encoding a statically defined object
 encode_fields([{Field, Type}|TypesLeft],
               [{Field,  Val}|FieldsLeft], E, Vsn, Types) ->
@@ -457,6 +584,9 @@ rlp_encode(Fields) ->
 %% Type registration and validation code
 
 register_types(Types) when is_map(Types) ->
+    register_types(latest_vsn(), Types).
+
+register_types(Vsn, Types) ->
     Codes = maps:get(codes, Types, #{}),
     Rev   = rev_codes(Codes),
     Templates = maps:get(templates, Types, #{}),
@@ -473,16 +603,49 @@ register_types(Types) when is_map(Types) ->
     assert_sizes(Merged),
     assert_mappings(Merged),
     Merged1 = assert_label_cache(Merged),
-    put_types(Merged1).
+    put_types(Vsn, Merged1).
+
+latest_vsn() ->
+    case persistent_term:get(pt_key(), undefined) of
+        undefined -> ?VSN;
+        #{latest_vsn := V} ->
+            V
+    end.
+
+pt_key() -> {?MODULE, types}.
 
 put_types(Types) ->
-    persistent_term:put({?MODULE, types}, Types).
+    put_types(types_vsn(Types), Types).
+
+put_types(V, Types) ->
+    K = pt_key(),
+    Old = case persistent_term:get(K, undefined) of
+              undefined -> default_types_pt();
+              Existing -> Existing
+          end,
+    put_types_(K, V, Types, Old).
+
+put_types_(K, V, Types, #{latest_vsn := V0, types := Types0} = Old) ->
+    New = case V > V0 of
+              true  ->
+                  Old#{latest_vsn := V,
+                       types      := Types0#{V => Types#{vsn => V}}};
+              false ->
+                  Old#{types := Types0#{V => Types#{vsn => V}}}
+          end,
+    persistent_term:put(K, New).
 
 types_from_list(L) ->
-    lists:foldl(fun elem_to_type/2, dynamic_types(), L).
+    types_from_list(L, registered_types()).
 
-register_type(Code, Tag, Template) when is_integer(Code), Code >= 0 ->
-    #{codes := Codes, rev := Rev, templates := Temps} = Types = registered_types(),
+types_from_list(L, Types) ->
+    gmser_dyn_types:from_list(L, Types).
+
+register_type(Code, Tag, Template) ->
+    register_type(latest_vsn(), Code, Tag, Template).
+
+register_type(Vsn, Code, Tag, Template) when is_integer(Code), Code >= 0 ->
+    #{codes := Codes, rev := Rev, templates := Temps} = Types = registered_types(Vsn),
     case {is_map_key(Code, Codes), is_map_key(Tag, Rev)} of
         {false, false} ->
             New = Types#{ codes     := Codes#{Code => Tag}
@@ -515,37 +678,11 @@ cache_label(Code, Label) when is_integer(Code), Code >= 0, is_atom(Label) ->
         {_,true} -> error(code_exists)
     end.
 
-elem_to_type({Tag, Code, Template}, Acc) when is_atom(Tag), is_integer(Code) ->
-    #{codes := Codes, rev := Rev, templates := Temps} = Acc,
-    case {is_map_key(Tag, Rev), is_map_key(Code, Codes)} of
-        {false, false} ->
-            Acc#{ codes := Codes#{Code => Tag}
-                , rev := Rev#{Tag => Code}
-                , templates => Temps#{Tag => Template}
-                };
-        {true, _} -> error({duplicate_tag, Tag});
-        {_, true} -> error({duplicate_code, Code})
-    end;
-elem_to_type({labels, Lbls}, Acc) ->
-    lists:foldl(fun add_label/2, Acc, Lbls);
-elem_to_type(Elem, _) ->
-    error({invalid_type_list_element, Elem}).
-
-add_label({L, Code}, #{labels := Lbls, rev_labels := RevLbls} = Acc)
-  when is_atom(L), is_integer(Code), Code > 0 ->
-    case {is_map_key(L, Lbls), is_map_key(Code, RevLbls)} of
-        {false, false} ->
-            Acc#{labels := Lbls#{L => Code},
-                 rev_labels := RevLbls#{Code => L}};
-        {true, _} -> error({duplicate_label, L});
-        {_, true} -> error({duplicate_label_code, Code})
-    end;
-add_label(Elem, _) ->
-    error({invalid_label_elem, Elem}).
-
-
 revert_to_default_types() ->
-    persistent_term:put({?MODULE, types}, dynamic_types()).
+    persistent_term:put(pt_key(), default_types_pt()).
+
+default_types_pt() ->
+    #{latest_vsn => ?VSN, types => #{?VSN => dynamic_types()}}.
 
 assert_sizes(#{codes := Codes, rev := Rev, templates := Ts} = Types) ->
     assert_sizes(map_size(Codes), map_size(Rev), map_size(Ts), Types).
@@ -664,6 +801,10 @@ dynamic_types_test_() ->
     , ?_test(t_missing_labels())
     ].
 
+versioned_types_test_() ->
+    [ ?_test(t_new_version())
+    ].
+
 t_round_trip(T) ->
     ?debugVal(T),
     ?assertMatch({T, T}, {T, decode(encode(T))}).
@@ -719,7 +860,6 @@ t_reg_template_vsnd_fun() ->
     E = encode_typed(tup2f1, {3,4}),
     {3,4} = decode(E),
     ok.
-                       
 
 t_reg_label_cache() ->
     Enc0 = gmser_dyn:encode('1'),
@@ -743,7 +883,7 @@ t_reg_label_cache() ->
     ?assertNotEqual(Enc0a, Enc1a).
 
 t_reg_label_cache2() ->
-    TFromL = gmser_dyn:types_from_list(
+    TFromL = types_from_list(
                [ {lbl_tup2, 1003, {label, label}}
                , {labels,
                   [{'1', 49}]}
@@ -764,8 +904,16 @@ t_reg_options() ->
 
 t_typed_map() ->
     Term = #{a => 13, {key,1} => [a]},
-    Enc = encode_typed(#{items => [{a,int},{{key,1},[label]}]}, Term),
-    ?assertEqual(Term, decode(Enc)).
+    Items = [{a,int},{{key,1},[label]}],
+    OptItems = [{opt, b, int} | Items],
+    Enc = encode_typed(#{items => Items}, Term),
+    ?assertEqual(Term, decode(Enc)),
+    ?assertEqual(Enc,  encode_typed(#{items => Items}, Term)),
+    ?assertEqual(Enc,  encode_typed(#{items => OptItems}, Term)),
+    Term1 = Term#{b => 4},
+    Enc1 = encode_typed(#{items => OptItems}, Term1),
+    ?assertEqual(Term1, decode(Enc1)),
+    ?assertEqual(Enc, encode_typed(#{items => Items}, Term1)).
 
 t_alts() ->
     t_round_trip_typed(#{alt => [negint, int]}, -4),
@@ -786,4 +934,22 @@ t_missing_labels() ->
     true = is_atom(gmser_dyn:decode(EncNewAm, set_opts(#{missing_labels => create}))),
     ok.
 
+t_new_version() ->
+    V = latest_vsn(),
+    Types0 = registered_types(V),
+    V1 = V+1,
+    Types1 = types_from_list([{vsn, V1},
+                              {msg1, 300, {int, int}}], Types0),
+    T2 = {3,5},
+    Enc21 = encode_typed(msg1, T2, Types1),
+    T2 = decode(Enc21, Types1),
+    V2 = V1+1,
+    Types2 = types_from_list([{vsn, V2},
+                              {modify, {msg1, {int, int, int}}}], Types1),
+    Enc21 = encode_typed(msg1, T2, Types1),
+    try encode_typed(msg1, T2, Types2) catch error:_ -> ok end,
+    T3 = {3,5,7},
+    Enc32 = encode_typed(msg1, T3, Types2),
+    T3 = decode(Enc32, Types2).
+
 -endif.