diff --git a/src/tools/mana_replay_api.h b/src/tools/mana_replay_api.h
index f6e2bec..fab9fec 100644
--- a/src/tools/mana_replay_api.h
+++ b/src/tools/mana_replay_api.h
@@ -9,7 +9,7 @@ extern "C"
 #endif
 {
 
-// descriptors - daq structure
+// descriptors - daq tree structure
 // daq   -> events   -> modules -> data_sources
 // alternative concepts:
 // crate -> triggers -> modules -> data_sources
@@ -18,10 +18,18 @@ extern "C"
 // todo: add number of valid bits in the data source
 // todo: rng handling?
 
+typedef enum
+{
+  dt_uint32,
+  dt_float,
+} data_type_t;
+
 typedef struct
 {
-    const char *name;
-    size_t size;
+    const char *array_name;
+    data_type_t data_type;
+    size_t array_size;
+    size_t valid_bits; // belongs into data_type_t
 } array_descriptor_t;
 
 typedef struct
@@ -46,15 +54,17 @@ typedef struct
     size_t event_count;
 } run_descriptor_t;
 
-typedef struct
-{
-    const float *data;
-    size_t size;
-} const_span_t;
+// data views - daq data
 
 typedef struct
 {
-    const_span_t *data_arrays;
+    float *data;
+    size_t size;
+} array_t;
+
+typedef struct
+{
+    array_t *data_arrays;
     size_t data_array_count;
 } module_data_t;