Venice identifiers are used for user IDs, community aliases, and conference aliases (and maybe other unique identifiers in the future). A valid Venice ID consists of characters from the following character set only:
All characters are represented in the ISO 8859-1 character set. Also note that all Venice identifiers are case-insensitive.
Rationale
The character set was defined starting with the list of characters allowable in URL path components ("pchar" as defined in RFC 2396, section 3.3, page 14), so that Venice IDs would be usable as "path information" in a URL.
The ampersand [&] was eliminated because of its possible confusion with a URL parameter separator, and because it requires HTML escaping.
The at sign [@] was eliminated because of possible confusion with email addresses and Jabber IDs.
The plus sign [+] was eliminated because of possible confusion with a URL-encoded space character.
The comma [,] was eliminated because of its possible interpretation as a separator character.
The equals sign [=] was eliminated because of its possible confusion with a URL parameter/value separator.
The colon [:] was withheld to provide for a possible future "namespace" expansion (as in XML namespaces).
The parentheses [(, )] were eliminated because of possible confusion with user link syntax in conferencing.
The period [.] was eliminated because of possible confusion with post link syntax in conferencing.
The exclamation point [!] was eliminated because of possible confusion with extended post link syntax in conferencing.