Q: Does a commentary article have a DOI?
Does a commentary article have a DOI? While calculating impact factor, is this kind of article included in the denominator?
A DOI or Digital Object Identifier is a permanent identification number assigned to published works. It can be assigned to book chapters, journal articles, datasets, etc. Since it can be assigned to any scientific publication, I see no reason why it should not be used for commentary articles. However, some journals/publishers may not be using DOIs. So if your journal hasn't asked for a DOI, probably the journal doesn't use it.
All articles published in a journal, irrespective of the article type, should ideally be taken into account while calculating the impact factor.