  Dereferencing a URI returns a representation of the current state of the
resource identified by that URI. But, on the Web representations of prior
states of a resource are also available, for example, as resource versions in
Content Management Systems or archival resources in Web Archives such as the
Internet Archive. This paper introduces a resource versioning mechanism that is
fully based on HTTP and uses datetime as a global version indicator. The
approach allows "follow your nose" style navigation both from the current
time-generic resource to associated time-specific version resources as well as
among version resources. The proposed versioning mechanism is congruent with
the Architecture of the World Wide Web, and is based on the Memento framework
that extends HTTP with transparent content negotiation in the datetime
dimension. The paper shows how the versioning approach applies to Linked Data,
and by means of a demonstrator built for DBpedia, it also illustrates how it
can be used to conduct a time-series analysis across versions of Linked Data
descriptions.
