+ /**
+ * Determines wether the username exists or not
+ *
+ * @return $exists Wether the username exists
+ */
+ function ifUsernameExists ();
+
+ /**
+ * Determines wether the email exists or not
+ *
+ * @return $exists Wether the email exists
+ */
+ function ifEmailAddressExists ();
+
+ /**
+ * Checks if the supplied password hash in request matches with the stored
+ * in database.
+ *
+ * @param $requestInstance A requestable class instance
+ * @return $matches Wether the supplied password hash matches
+ */
+ function ifPasswordHashMatches (Requestable $requestInstance);
+
+ /**
+ * Adds data for later complete update
+ *
+ * @param $column Column we want to update
+ * @param $value New value to store in database
+ * @return void
+ */
+ function addUpdateData ($column, $value);