For example, I see a "book" on Springer published in 2017 that is identical to a conference article presented in 2011. What is happening here?
In my opinion, duplicate publications are not good for the research community. I am annoyed because if I cite the Springer version in my paper, then the reader will see e.g., 2017 and think that the work was proposed in 2017 when actually it was proposed in e.g., 2011. Furthermore, if I come across a paper published in 20XX in Springer, I have to play detective to make sure there isn't a version 5 years old that is identical...
Edit1: I must point out that the "book" versions of the papers I am referring are not extended versions but instead are identical.
Edit2: So, the specific case I am thinking of is a paper presented at a conference. The publisher of the book and conference are both Springer, but I am confused as to why conference proceeding are being published 5 or more years after the conference.