diff --git a/include/types/arg.h b/include/types/arg.h
index c621025..cccc565 100644
--- a/include/types/arg.h
+++ b/include/types/arg.h
@@ -28,6 +28,8 @@
 #include <common/chunk.h>
 #include <common/mini-clist.h>
 
+#include <types/vars.h>
+
 /* encoding of each arg type : up to 31 types are supported */
 #define ARGT_BITS      5
 #define ARGT_NBTYPES   (1 << ARGT_BITS)
@@ -58,6 +60,7 @@
 	ARGT_USR,      /* a pointer to a user list */
 	ARGT_MAP,      /* a pointer to a map descriptor */
 	ARGT_REG,      /* a pointer to a regex */
+	ARGT_VAR,      /* contains a variable description. */
 };
 
 /* context where arguments are used, in order to help error reporting */
@@ -94,6 +97,7 @@
 	struct userlist *usr;
 	struct map_descriptor *map;
 	struct my_regex *reg;
+	struct var_desc var;
 };
 
 struct arg {
diff --git a/include/types/stream.h b/include/types/stream.h
index 4203af8..953f9d1 100644
--- a/include/types/stream.h
+++ b/include/types/stream.h
@@ -43,6 +43,7 @@
 #include <types/stream_interface.h>
 #include <types/task.h>
 #include <types/stick_table.h>
+#include <types/vars.h>
 
 
 /* Various Stream Flags, bits values 0x01 to 0x100 (shift 0) */
@@ -143,6 +144,9 @@
 
 	char **req_cap;                         /* array of captures from the request (may be NULL) */
 	char **res_cap;                         /* array of captures from the response (may be NULL) */
+	struct vars vars_sess;                  /* list of variables for the session scope. */
+	struct vars vars_txn;                   /* list of variables for the txn scope. */
+	struct vars vars_reqres;                /* list of variables for the request and resp scope. */
 
 	struct stream_interface si[2];          /* client and server stream interfaces */
 	struct strm_logs logs;                  /* logs for this stream */
diff --git a/include/types/vars.h b/include/types/vars.h
new file mode 100644
index 0000000..c387a77
--- /dev/null
+++ b/include/types/vars.h
@@ -0,0 +1,33 @@
+#ifndef _TYPES_VARS_H
+#define _TYPES_VARS_H
+
+#include <common/mini-clist.h>
+
+#include <types/sample.h>
+
+enum vars_scope {
+	SCOPE_SESS = 0,
+	SCOPE_TXN,
+	SCOPE_REQ,
+	SCOPE_RES,
+};
+
+struct vars {
+	struct list head;
+	enum vars_scope scope;
+	unsigned int size;
+};
+
+/* This struct describes a variable. */
+struct var_desc {
+	const char *name; /* Contains the normalized variable name. */
+	enum vars_scope scope;
+};
+
+struct var {
+	struct list l; /* Used for chaining vars. */
+	const char *name; /* Contains the variable name. */
+	struct sample_storage data; /* data storage. */
+};
+
+#endif