[Building Sakai] Question about sakai functions (i.e. permissions)

[Jim Eng]

The names (or identifiers?) for permissions in sakai seem to be strings made up of alphabetic characters (mostly lower-case?) and dots (like the one at the end of this sentence).  They also seem to be pretty short, usually no more than 20 or 30 characters.  For example, "content.read" or "annc.delete.own" are two permissions used in sakai core.   

The characteristics I mentioned seem to be conventions rather than requirements.  I don't see any documentation for any rules about what characters are valid/invalid or restrictions on length.    I am wondering whether there is anybody knows if there are any.  

I am asking because I need to store a short list of permissions in the database, and it would be easier to store them in a delimited string rather than storing them individually.  But I'd want to make sure the delimiter would never be used in a permission id and that the database column is big enough to store the entire string.  

It looks like function names are limited to 99 characters in the SAKAI_REALM_FUNCTION table, but I'm not sure that is guaranteed elsewhere.  

Suggestions appreciated.

Thanks.

Jim