Update DC.pm

[orazionelson]

official_url, id_number and doi are not relations but identifiers
Some services like https://www.base-search.net or Unpaywall don't keep the DOI if it is referenced as "relation"

[cziaarm]

Hi Alfredo,

While I agree wholeheartedly that the DOI should be an identifier and have had to override this for other systems to be able to harvest sensibly on occaision (altmetrics springs to mind). I wonder how many other systems might still be expecting the DOIs and such to appear as relation, especially as it has been this way for yonks.

What do you think to an additive change, in which we leave the (perhaps wrong) mapping between DOIs etc and relation, but add a mapping for identifiers?

Then I'm sure there is a debate to be had about whether a DOI that may resolve to a different instance of the digital object should be used as an identifier for the digital object held in the repository...

So on a practical level I'm behind this, if it were to add to rather than replace the current mapping, but would want some reassurance from the community and/or DC experts on the validity of such a change (even though it makes sense to me)

[ghost]

+1 to having DOI in both, I think that would be pragmatic given that DOI could be considered an identifier for a related item (the publisher's version), or for the repo version, or indeed for the work as an intellectual creation irrespective of version. Also, this would make this a non-breaking change.

official_url is a link to a related version IMHO and not an identifier