Reusing Requirements: Taking Advantage of What You Know

by Suzanne Robertson

When your friend who lives in the UK tells you that her new telephone number is 020 7262 3395, you write it down. You expect to use the number many times in the future so, rather than just jotting it onto a scrap of paper, you record it in your address book, your computer, or your PDA. This friend lives in inner London, as do you, so when you call this friend, you dial all the digits in the number. However, when you phone your friend from outside London, you know that the leading zero (internal district indicator) is not necessary, so you write the number as (0)20 7262 3395. Now, because this way of writing down phone numbers is very familiar, if you give this number to anyone else in the UK, there's a good chance they will know how to phone your friend.