Filename shall only contain valid characters.
Since there is no common standard which characters are allowed in AF3-Filenames and which are not, this feature may be used to discuss a minimum subset of characters for AF3-URIs, -URLs and filenames (see: org.fortiss.af3.project.ui.utils.FileNameValidatorUtil).
proposal 64 characters:
[a-zA-Z0-9] and [_-]
(from redmine: issue id 588, created on 2012-01-28, closed on 2012-07-03)