828-5000: what is this?
AB1234: what is this?
(For privacy issues, each of these has been changed, but they are in the same format as the actual data.)
The issue: You might know what these are if you knew the context they occur in. But maybe not. Sometimes, there is more than one interpretation. Assuming that it is obvious can lead to confusion.
The first is a phone number in British Columbia. Although we use 10-digit numbers now, quite often, people leave the area code off. Three digits, hyphen, four digits is the format for them. It was also the format for student numbers at Thompson Rivers University.
The second is one format of licence plate numbers in British Columbia. It is also the format for WIS employee numbers. Just after I qualified as a driver, the schedule had a job where I was driver. After my name was a sequence of two letters followed by four digits. I did not know what it meant. Finally, it occurred to me that it was the van’s licence plate number. (It might have been my supervisor’s employee number. The letters are surname and first given name initials, and they were right for him.)