From a hypothes.is Blog Post by John Udell:
Scientific journals come and go, but the scientific record is permanent, and its annotation layer should be too. New Hypothesis support for DOIs (digital object identifiers) helps ensure a robust connection between articles and annotations.
The scientific literature needs to be permanent. Journals may come and go, but articles will live on, and so should annotations that refer to them. The DOI enables a domain-independent connection between content and annotations. By taking better advantage of the DOI, Hypothesis now reinforces that connection.
Udell does a super job (as you would expect from J.U.) explaining how it all works. A very interesting and educational read.
Read the Complete Article