RFC 1439 (rfc1439) - Page 2 of 11
The Uniqueness of Unique Identifiers
Alternative Format: Original Text Document
RFC 1439 Uniqueness of Unique Identifiers March 1993
and duplicates are handled in an ad-hoc manner. Example identifiers
are:
Craig.Finseth
caf
Now that we have widespread electronic mail, an important feature of
an identifier system is the ability to predict the identifier based
on other information associated with the individual. This other
information is typically the person's name.
Methods two and three make such predictions possible, especially if
you have one example mapping from a person's name to the identifier.
Method two relies on using some or all of the name and
algorithmically varying it to ensure uniqueness (for example, by
appending an integer). Method three relies on using some or all of
the name and selects an alternate identifier in the case of a
duplication.
For both methods, it is important to minimize the need for making the
adjustments required to ensure uniqueness (i.e., an integer that is
not 1 or an alternate identifier). The probability that an
adjustment will be required depends on the format of the identifer
and the size of the organization.
2. Identifier Formats
There are a number of popular identifier formats. This section will
list some of them and supply both typical and maximum values for the
number of possible identifiers. A "typical" value is the number that
you are likely to run into in real life. A "maximum" value is the
largest number of possible (without getting extreme about it) values.
All ranges are expressed as a number of bits.
2.1 Initials
There are three popular formats based on initials: those with one,
two, or three letters. (The number of people with more than three
initials is assumed to be small.) Values:
format typical maximum
I 4 5
II 8 10
III 12 15
Finseth