+ * @brief Sets the app credential.
+ * @details Using this API, the application can set a credential.
+ * The credential is a key to verify the authorization about using the engine.
+ * If the application sets the credential, it will be able to use functions of the engine entirely.
+ * @since_tizen @if MOBILE 3.0 @elseif WEARABLE 2.3.2 @endif
+ * @remarks The necessity of the credential depends on the engine. In case of the engine which is basically embedded in Tizen, the credential is not necessary so far.
+ * However, if the user wants to apply the 3rd party's engine, the credential may be necessary. In that case, please follow the policy provided by the corresponding engine.
+ * @param[in] stt The STT handle
+ * @param[in] credential The app credential
+ * @return @c 0 on success,
+ * otherwise a negative error value
+ * @retval #STT_ERROR_NONE Success
+ * @retval #STT_ERROR_INVALID_PARAMETER Invalid parameter
+ * @retval #STT_ERROR_INVALID_STATE Invalid state
+ * @retval #STT_ERROR_NOT_SUPPORTED STT NOT supported
+ * @pre The state should be #STT_STATE_CREATED or #STT_STATE_READY.
+ * @see stt_start()
+*/
+int stt_set_credential(stt_h stt, const char* credential);
+
+
+/**
+ * @brief Sets the private data to stt engine.
+ * @details The private data is the setting parameter for applying keys provided by the engine.
+ * Using this API, the application can set the private data and use the corresponding key of the engine.
+ * For example, if the engine provides 'partial recognition' as a recognition type, the application can set the private data as the following.
+ * int ret = stt_set_private_data(stt_h, "recognition_type", "PARTIAL");
+ * @since_tizen @if MOBILE 3.0 @elseif WEARABLE 2.3.2 @endif
+ * @remarks If the engine is replaced with the other engine, the key may be ignored.
+ * @param[in] stt The STT handle
+ * @param[in] key The field name of private data
+ * @param[in] data The data for set
+ * @return @c 0 on success,
+ * otherwise a negative error value
+ * @retval #STT_ERROR_NONE Successful
+ * @retval #STT_ERROR_INVALID_PARAMETER Invalid parameter
+ * @retval #STT_ERROR_INVALID_STATE Invalid state
+ * @retval #STT_ERROR_NOT_SUPPORTED STT NOT supported
+ * @retval #STT_ERROR_TIMED_OUT No answer from the STT service
+ * @pre The state should be #STT_STATE_READY.
+ * @see stt_get_private_data()
+*/
+int stt_set_private_data(stt_h stt, const char* key, const char* data);
+
+
+/**
+ * @brief Gets the private data from stt engine.
+ * @details The private data is the information provided by the engine.
+ * Using this API, the application can get the private data which corresponds to the key from the engine.
+ * @since_tizen @if MOBILE 3.0 @elseif WEARABLE 2.3.2 @endif
+ * @remarks If the engine is replaced with the other engine, the key may be ignored.
+ * @remarks The @a data must be released using free() when it is no longer required.
+ * @param[in] stt The STT handle
+ * @param[in] key The field name of private data
+ * @param[out] data The data field of private data
+ * @return @c 0 on success,
+ * otherwise a negative error value
+ * @retval #STT_ERROR_NONE Successful
+ * @retval #STT_ERROR_INVALID_PARAMETER Invalid parameter
+ * @retval #STT_ERROR_INVALID_STATE Invalid state
+ * @retval #STT_ERROR_NOT_SUPPORTED STT NOT supported
+ * @retval #STT_ERROR_TIMED_OUT No answer from the STT service
+ * @pre The state should be #STT_STATE_READY.
+ * @see stt_set_private_data()
+*/
+int stt_get_private_data(stt_h stt, const char* key, char** data);
+
+
+/**
+ * @brief Connects the STT service asynchronously.