diff --git a/src/machi_dt.erl b/src/machi_dt.erl
new file mode 100644
index 0000000..6d94e6d
--- /dev/null
+++ b/src/machi_dt.erl
@@ -0,0 +1,70 @@
+%% -------------------------------------------------------------------
+%%
+%% Copyright (c) 2007-2015 Basho Technologies, Inc.  All Rights Reserved.
+%%
+%% This file is provided to you under the Apache License,
+%% Version 2.0 (the "License"); you may not use this file
+%% except in compliance with the License.  You may obtain
+%% a copy of the License at
+%%
+%%   http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing,
+%% software distributed under the License is distributed on an
+%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+%% KIND, either express or implied.  See the License for the
+%% specific language governing permissions and limitations
+%% under the License.
+%%
+%% -------------------------------------------------------------------
+
+-module(machi_dt).
+
+-include("machi_projection.hrl").
+
+-type chunk()       :: chunk_bin() | {chunk_csum(), chunk_bin()}.
+-type chunk_bin()   :: binary() | iolist().    % client can use either
+-type chunk_csum()  :: binary().               % 1 byte tag, N-1 bytes checksum
+-type chunk_summary() :: {file_offset(), chunk_size(), binary()}.
+-type chunk_s()     :: binary().               % server always uses binary()
+-type chunk_pos()   :: {file_offset(), chunk_size(), file_name_s()}.
+-type chunk_size()  :: non_neg_integer().
+-type error_general() :: 'bad_arg' | 'wedged' | 'bad_checksum'.
+-type epoch_csum()  :: binary().
+-type epoch_num()   :: -1 | non_neg_integer().
+-type epoch_id()    :: {epoch_num(), epoch_csum()}.
+-type file_info()   :: {file_size(), file_name_s()}.
+-type file_name()   :: float().%%%binary() | list().
+-type file_name_s() :: binary().                % server reply
+-type file_offset() :: non_neg_integer().
+-type file_size()   :: non_neg_integer().
+-type file_prefix() :: binary() | list().
+-type inet_host()   :: inet:ip_address() | inet:hostname().
+-type inet_port()   :: inet:port_number().
+-type projection()      :: #projection_v1{}.
+-type projection_type() :: 'public' | 'private'.
+
+-export_type([
+              chunk/0,
+              chunk_bin/0,
+              chunk_csum/0,
+              chunk_summary/0,
+              chunk_s/0,
+              chunk_pos/0,
+              chunk_size/0,
+              error_general/0,
+              epoch_csum/0,
+              epoch_num/0,
+              epoch_id/0,
+              file_info/0,
+              file_name/0,
+              file_name_s/0,
+              file_offset/0,
+              file_size/0,
+              file_prefix/0,
+              inet_host/0,
+              inet_port/0,
+              projection/0,
+              projection_type/0
+             ]).
+