Activity identifier refers to a specific identifying piece of information that is unique to each particular activity. This activity identifier can be made up of text (for example, “NEW YORK” or “HOME”, or it can be numeric in nature (for example, “34564” or “00001”). It can also be a combination of the two (for example, “A-1” or “4554R”). These unique activity identifiers are assigned to each schedule activity, the most essential reason for which is to differentiate that specific project activity from other project activities. Often times, actual project names within the umbrella activity are completely eschewed in the course of general discussion in favor of the sole usage of the activity identifier, which is typically far easier to distinguish from other activity codes than project titles may be, many of which are very similar in nature. These activity identifiers are also typically unique within each individual project schedule network diagram.
This term is defined in the 3rd and the 4th edition of the PMBOK.
