Rules for naming files and folders are an important part of the standards. Correctly named folders make it easier to maintain clean archives and unique filenames allow dupecheck to work properly. There's a defined character set which can be used in naming of the folders. The selected character set is chosen to minimize problems due to the many platforms a release may encounter during its distribution. Since FTP servers, operating systems or file systems may not allow special characters in file or directory names, only a small set of characters is allowed. Substitutions are made where special characters would normally be used (e.g. "ç" replaced by "c") or these characters are omitted, such as an apostrophe. This can happen automatically by site scripts. As a note, spaces are explicitly disallowed in current standards and are substituted with underscores or full stops.