  Scholarly resources, just like any other resources on the web, are subject to
reference rot as they frequently disappear or significantly change over time.
Digital Object Identifiers (DOIs) are commonplace to persistently identify
scholarly resources and have become the de facto standard for citing them. We
investigate the notion of persistence of DOIs by analyzing their resolution on
the web. We derive confidence in the persistence of these identifiers in part
from the assumption that dereferencing a DOI will consistently return the same
response, regardless of which HTTP request method we use or from which network
environment we send the requests. Our experiments show, however, that
persistence, according to our interpretation, is not warranted. We find that
scholarly content providers respond differently to varying request methods and
network environments and even change their response to requests against the
same DOI. In this paper we present the results of our quantitative analysis
that is aimed at informing the scholarly communication community about this
disconcerting lack of consistency.
