[OAI-implementers] Re: question about the date in OAI-PMH

[Simeon Warner]

On Tue, 24 Sep 2002, Mei Ran wrote:
> Hi,
> 
> I'm not sure if I'm right for all the dates in the OAI. would you like
> to give me some help:
> 
> 1. the earliestDatestamp in Identify response. is this refer to the
> resource creation or modification time?

The earliestDatestamp is a datestamp that is earlier than or equal to the
earliest datestamp for any metadata RECORD in the repository. Datestamps
in OAI refer to the last addition, delete or modification of RECORDS and
not resources. (The metadata records themselves describe resources. The 
semantics of the metadata are outside the scope of OAI-PMH, they are 
defined, for example, by Dublib Core.)

Definition of resource, item, record in OAI:
http://www.openarchives.org/OAI/2.0/openarchivesprotocol.htm#Repository
Definition of Identify response with earliestDate element:
http://www.openarchives.org/OAI/2.0/openarchivesprotocol.htm#Identify
Datestamps in OAI:
http://www.openarchives.org/OAI/2.0/openarchivesprotocol.htm#DatestampsResponses
 
> 2. the Date in metadata, DC. is this refer to resource creation or
> modification time too?

The metadata is about the resource, so yes broadly speaking.

Definition of Date element in unqualified DC:
http://dublincore.org/documents/1999/07/02/dces/#date 

> 3. the datestamp in the header of DC. I think this one should refer to
> the creation or modification of the item in the repository, is that
> right?

The OAI record header is not part of the DC (or other format) metadata.

See answer to 1). However, you now mention 'item' which is slightly
different. In OAI-PMH v2.0 (change from v1.1) an item is conceptually
some union or source of the all the metadata records corresponding
to a particular identifier. No datestamp is exposed for items, just
for the metadata records.

In practice, it may be the case that the item is the thing inside the 
repository that has a datestamp. In that case all records disseminated
from the item (all metadata formats) will have that datestamp.

Definition of 'item' in OAI:
http://www.openarchives.org/OAI/2.0/openarchivesprotocol.htm#Item
Section 3 of the Repository Guidelines also notes some issues with 
datestamps:
http://www.openarchives.org/OAI/2.0/guidelines-repository.htm

Cheers,
Simeon


> Thank you very much for your help!
> 
> Mei
> 
> *******************************************
> Mei Ran
> Research Assistant
> Computer Science Dept., Univ. of Tennessee
> http://www.cs.utk.edu/~ran
> Tel: (865) 974-6722
> *******************************************
>