+int uc_get_hits (const data_set_t *ds, const value_list_t *vl);
+int uc_set_hits (const data_set_t *ds, const value_list_t *vl, int hits);
+int uc_inc_hits (const data_set_t *ds, const value_list_t *vl, int step);
+
+int uc_get_history (const data_set_t *ds, const value_list_t *vl,
+ gauge_t *ret_history, size_t num_steps, size_t num_ds);
+int uc_get_history_by_name (const char *name,
+ gauge_t *ret_history, size_t num_steps, size_t num_ds);
+
+/*
+ * Meta data interface
+ */
+int uc_meta_data_exists (const value_list_t *vl, const char *key);
+int uc_meta_data_delete (const value_list_t *vl, const char *key);
+
+int uc_meta_data_add_string (const value_list_t *vl,
+ const char *key,
+ const char *value);
+int uc_meta_data_add_signed_int (const value_list_t *vl,
+ const char *key,
+ int64_t value);
+int uc_meta_data_add_unsigned_int (const value_list_t *vl,
+ const char *key,
+ uint64_t value);
+int uc_meta_data_add_double (const value_list_t *vl,
+ const char *key,
+ double value);
+int uc_meta_data_add_boolean (const value_list_t *vl,
+ const char *key,
+ _Bool value);
+
+int uc_meta_data_get_string (const value_list_t *vl,
+ const char *key,
+ char **value);
+int uc_meta_data_get_signed_int (const value_list_t *vl,
+ const char *key,
+ int64_t *value);
+int uc_meta_data_get_unsigned_int (const value_list_t *vl,
+ const char *key,
+ uint64_t *value);
+int uc_meta_data_get_double (const value_list_t *vl,
+ const char *key,
+ double *value);
+int uc_meta_data_get_boolean (const value_list_t *vl,
+ const char *key,
+ _Bool *value);