+int data_provider_get_ident_ds_names (graph_ident_t *ident,
+ dp_list_get_ident_ds_names_callback callback, void *user_data);
+int data_provider_get_ident_data (graph_ident_t *ident,
+ const char *ds_name,
+ dp_time_t begin, dp_time_t end,
+ dp_get_ident_data_callback callback, void *user_data);