  As Digital Libraries (DL) become more aligned with the web architecture,
their functional components need to be fundamentally rethought in terms of URIs
and HTTP. Annotation, a core scholarly activity enabled by many DL solutions,
exhibits a clearly unacceptable characteristic when existing models are applied
to the web: due to the representations of web resources changing over time, an
annotation made about a web resource today may no longer be relevant to the
representation that is served from that same resource tomorrow. We assume the
existence of archived versions of resources, and combine the temporal features
of the emerging Open Annotation data model with the capability offered by the
Memento framework that allows seamless navigation from the URI of a resource to
archived versions of that resource, and arrive at a solution that provides
guarantees regarding the persistence of web annotations over time. More
specifically, we provide theoretical solutions and proof-of-concept
experimental evaluations for two problems: reconstructing an existing
annotation so that the correct archived version is displayed for all resources
involved in the annotation, and retrieving all annotations that involve a given
archived version of a web resource.
