[OAI-implementers] LatestDatestamp?

Martin Malmsten martin.malmsten@libris.kb.se
Wed, 21 Apr 2004 00:52:12 +0200

> You probably cannot safely use the timestamps that come with the records
> in this file. The record datestamps in the OAI record headers must be the
> timestamps when the material becomes available (subject to chosen
> granularity). Adding material with a datestamp before the current time
> means that records can be missed in incremental harvests.
That was what I was afraid of. This means that if you build chains if
OAI-servers, data will be delivered in larger and larger chunks since
you cannot use the timestamp from the originating server (or the
original metadata).

> It is not clear why you want to expose the latest datestamp. Harvesters
> will usually harvest either all content, or content from the previous
> incremental harvest datestamp onward (no until date). In both cases newly
> added records will be successfully harvested.
Well, if you have a latest datestamp, then you can harvest from the
previous datestamp until the latest, and if records are added with a
datestamp that is after that datestamp (but before the time you
harvested) you would still get that record next time around.

This would ofcourse add some complexity to the procedure, so it's
probably not worth it. It'll be fun for the clients though, no records
for two weeks, then about 30.000, and then nothing for two weeks ... :)