Registry can currently generate random numbers using (#). It may be useful to also generate random strings as part of, or entirely as, identifiers. Certain characteristics of these strings may be useful:

• Lower/Upper case only, to avoid case folding issues (maybe only allow lower or upper, by using 'S' for uppercase strings and 's' for lowercase strings)
• Ranges (eg: a-f only)
• Relatedly, including numbers as potential string characters

For example, a 9 character hexadecimal string with a hyphen in the middle could be specified as

(s,0123456789abcdef:4)-(s,0123456789abcdef:4)