diff --git a/doc/tech_report.tex b/doc/tech_report.tex
index 561d69a0ac4d9437c826735f71b919a3ca04464f..7e9d6a86bb2f4c57740b665a15bbe036b060ce21 100644
--- a/doc/tech_report.tex
+++ b/doc/tech_report.tex
@@ -169,6 +169,22 @@ language covering most common use-cases.
sample string a_string;
\end{verbatim}
+\subsection{The void type}
+
+There is a type, \verb+void+, which can be used to send
+a sample that contains no data.
+
+\begin{verbatim}
+typedef void an_empty_type;
+
+sample an_empty_type no_data1;
+sample void no_data2;
+\end{verbatim}
+
+\verb+void+ type can may not be used as a field in a struct or
+the element type of an array.
+
+
\subsection{Arrays}
\begin{verbatim}
@@ -198,7 +214,46 @@ only arrays of arrays.
} a_struct;
\end{verbatim}
-\section{User defined types}
+\subsection{Sample type refereces}
+
+In addition to the primitive types, a sample may contain
+a reference to a sample type. References are declared using
+the \verb+sample+ keyword.
+
+Examples:
+
+\begin{verbatim}
+sample sample a_ref;
+
+sample sample ref_list[4];
+
+sample struct {
+ sample ref1;
+ sample ref2;
+ int x;
+ int y;
+} refs_and_ints;
+\end{verbatim}
+
+Sample references are need to be registered on both encoder and decoder
+side, using the functions
+
+\begin{verbatim}
+int labcomm_decoder_sample_ref_register(
+ struct labcomm_decoder *decoder\nonumber
+ const struct labcomm_signature *signature);
+
+int labcomm_encoder_sample_ref_register(
+ struct labcomm_encoder *encoder\nonumber
+ const struct labcomm_signature *signature);
+\end{verbatim}
+
+The value of an unregistered sample reference will be decoded as \verb+null+.
+
+\subsection{User defined types}
+
+User defined types are declared with the \verb+typedef+ reserved word,
+and can then be used in type and sample declarations.
\begin{verbatim}
typedef struct {
@@ -469,6 +524,7 @@ Field ::= Type <Name:String>;
abstract Type;
VoidType : Type;
+SampleRefType : Type;
PrimType : Type ::= <Name:String> <Token:int>;
UserType : Type ::= <Name:String>;
StructType : Type ::= Field*;
@@ -526,42 +582,50 @@ The built-in data types are encoded as follows:
\subsection{Protocol grammar}
\label{sec:ConcreteGrammar}
\begin{lstlisting}[basicstyle=\footnotesize\ttfamily]
-<packet> := <id> <length> ( <version> |
- <type_decl> |
- <sample_decl> |
- <type_binding> |
- <sample_data> )
-<version> := <string>
-<sample_decl> := <sample_id> <string> <type>
-<type_decl> := <type_id> <string> <type>
-<type_binding> := <sample_id> <type_id>
-<user_id> := 0x40..0xffffffff
+<packet> := <id> <length> ( <version> |
+ <type_decl> |
+ <sample_decl> |
+ <sample_ref> |
+ <type_binding> |
+ <sample_data> )
+<version> := <string>
+<sample_decl> := <sample_id> <string> <type>
+<sample_ref> := <sample_id> <string> <type>
+<type_decl> := <type_id> <string> <type>
+<type_binding> := <sample_id> <type_id>
+<user_id> := 0x40..0xffffffff
<sample_id> : <user_id>
<type_id> : <user_id>
-<string> := <string_length> <char>*
-<string_length>:= 0x00..0xffffffff
-<char> := any UTF-8 char
-<type> := <length> ( <basic_type> | <array_decl> | <struct_decl> | <type_id> )
-<basic_type> := ( <boolean_type> | <byte_type> | <short_type> |
- <integer_type> | <long_type> | <float_type> |
- <double_type> | <string_type> )
-<boolean_type> := 0x20
-<byte_type> := 0x21
-<short_type> := 0x22
-<integer_type> := 0x23
-<long_type> := 0x24
-<float_type> := 0x25
-<double_type> := 0x26
-<string_type> := 0x27
-<array_decl> := 0x10 <number_of_indices> <indices> <type>
-<number_of_indices> := 0x00..0xffffffff
-<indices> := ( <variable_index> | <fixed_index> )*
-<variable_index> := 0x00
-<fixed_index> := 0x01..0xffffffff
-<struct_decl> := 0x11 <number_of_fields> <field>*
-<number_of_fields> := 0x00..0xffffffff
-<field> := <string> <type>
-<sample_data> := packed sample data sent in network order, with
+<string> := <string_length> <char>*
+<string_length> := 0x00..0xffffffff
+<char> := any UTF-8 char
+<type> := <length> ( <basic_type> |
+ <array_decl> |
+ <struct_decl> |
+ <type_id> )
+<basic_type> := ( <void_type> | <boolean_type> | <byte_type> | <short_type> |
+ <integer_type> | <long_type> | <float_type> |
+ <double_type> | <string_type> | <sample_ref_type>)
+
+<void_type> := <struct_decl> 0 //void is encoded as empty struct
+<boolean_type> := 0x20
+<byte_type> := 0x21
+<short_type> := 0x22
+<integer_type> := 0x23
+<long_type> := 0x24
+<float_type> := 0x25
+<double_type> := 0x26
+<string_type> := 0x27
+<sample_ref_type> := 0x28
+<array_decl> := 0x10 <nbr_of_indices> <indices> <type>
+<nbr_of_indices> := 0x00..0xffffffff
+<indices> := ( <variable_index> | <fixed_index> )*
+<variable_index> := 0x00
+<fixed_index> := 0x01..0xffffffff
+<struct_decl> := 0x11 <nbr_of_fields> <field>*
+<nbr_of_fields> := 0x00..0xffffffff
+<field> := <string> <type>
+<sample_data> := packed sample data sent in network order, with
primitive type elements encoded according to
the sizes above
\end{lstlisting}
@@ -571,8 +635,9 @@ The labcomm sytem packet ids are:
\begin{lstlisting}[basicstyle=\footnotesize\ttfamily]
version: 0x01
sample_decl: 0x02
-type_decl: 0x03
-type_binding: 0x04
+sample_ref: 0x03
+type_decl: 0x04
+type_binding: 0x05
\end{lstlisting}
Note that since the signature transmitted in a \verb+<sample_def>+ is
flattened, the \verb+<type>+ transmitted in a \verb+<sample_def>+ may
diff --git a/lib/python/labcomm/LabComm.py b/lib/python/labcomm/LabComm.py
index b3b6dd6d8acef3124588fc0811bb97bab380e1eb..3816c0f834cf6da92928a85cc6ee2caa868988bf 100644
--- a/lib/python/labcomm/LabComm.py
+++ b/lib/python/labcomm/LabComm.py
@@ -29,11 +29,29 @@
# | ...
# +----+--
#
+# LabComm2014 SAMPLE_REF:
+#
+# +----+----+----+----+
+# | id = 0x03 (packed32)
+# +----+----+----+----+
+# | length (packed32)
+# +----+----+----+----+
+# | type number (packed32)
+# +----+----+----+----+
+# | type name (UTF8)
+# | ...
+# +----+----+----+----+
+# | signature length (packed32)
+# +----+----+----+----+
+# | type signature
+# | ...
+# +----+--
+#
# LabComm2014 TYPE_DEF: (as SAMPLE_DEF, but signatures are hierarchical,
# i.e., may contain references to other types
#
# +----+----+----+----+
-# | id = 0x03 (packed32)
+# | id = 0x04 (packed32)
# +----+----+----+----+
# | length (packed32)
# +----+----+----+----+
@@ -51,7 +69,7 @@
# LabComm2014 TYPE_BINDING
#
# +----+----+----+----+
-# | id = 0x04 (packed32)
+# | id = 0x05 (packed32)
# +----+----+----+----+
# | length (packed32)
# +----+----+----+----+