Package: debian-policy Section 2.3.1 says: "Package names must consist of lower case letters (a-z), digits (0-9), plus (+) and minus (-) signs, and periods (.)."
It should say something like: "Package names must not consist of anything other than lower case letters (a-z), digits (0-9), plus (+) and minus (-) signs, and periods (.)." because it is not desirable, and not the current convention to make packages contain all of the items in the list. eg why force apt to have digits, plus and minus signs and periods. It would have to have a name like apt00+-.. to be valid. Drew Daniels