When Should Identifications Be Immutable?

After watching a presentation on Clojure and its immutable data structures, I began to wonder when should identifications be immutable?

Note that I said when should identifications… which means I am not advocating a universal position for all identifiers but rather a choice that may vary from situation to situation.

We may change our minds about an identification, the fact remains that at some point (dare I say state?) a particular identification was made.

For example, you make a intimate gesture at a party only to discover your spouse wasn’t the recipient of the gesture. But at the time you made the gesture, at least I am willing to believe, you thought it was your spouse. New facts are now apparent. But it is also a new identification. As your spouse will remind you, you did make a prior, incorrect identification.

As I recall, topics (and other information items) are immutable for purposes of merging. (TMDM, 6.2 and following.) That is merging results in a new topic or other new information item. On the other hand, merging also results in updating information items other than the one subject to merging. So those information items are not being treated as immutable.

But since the references are being updates, I don’t think it would be inconsistent with the TMDM to create new information items to be the carriers of the new identifiers and thus treating the information items as immutable.

Would be application/requirement specific but say for accounting/banking/securities and similar applications, it may be important for identifications to be immutable. Such that we can “unroll” a topic map as it were to any prior arbitrary identification or state.

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