[OAI-implementers] Question on flow control / resumption token

[Michael Nelson]

Moray,

The spec calls resumptionToken an "exclusive" argument, meaning that it is 
the only argument that should be used.  from section 4:

# exclusive, the argument may be included with request, but must be the 
only argument (in addition to the verb argument).

this means your rT "abcdefgh" must logically encode the other arguments: 
set, from, until, etc. as well as the cursor through the result set.

this can be done in two ways:

1.  server-side result set (supported in some systems)

2.  encoded in the rT itself (the most common approach).

some these rTs are opaque, e.g.:

http://edoc.hu-berlin.de/OAI-2.0?verb=ListIdentifiers&metadataPrefix=oai_dc 
-->
http://edoc.hu-berlin.de/OAI-2.0?verb=ListIdentifiers&resumptionToken=1309451189

and some are not, e.g.:

http://amsacta.cib.unibo.it/cgi/oai2?verb=ListIdentifiers&metadataPrefix=oai_dc 
-->
http://amsacta.cib.unibo.it/cgi/oai2?verb=ListIdentifiers&resumptionToken=metadataPrefix%3Doai_dc%26offset%3D1908

It is quite dated now, but here are the slides from a tutorial we gave at 
JCDL 2003:

http://www.cs.odu.edu/~mln/jcdl03/oai-2.0-adv.ppt

but there is some guidance on different strategies for creating rTs.

hope this helps,

Michael

On Thu, 30 Jun 2011, Moray McConnachie wrote:

> Hi,
>
> We're implementing a repository in OAI-PMH (not public at this stage),
> and I have a query where the specification isn't very clear.
>
> It's about flow control.
>
> Taking ListIdentifiers as an example, is the resumptionToken the ONLY
> argument which a client MUST supply to resume an incomplete list? Or
> must they also supply the other original arguments?
>
> Or to put it another way, if we receive a query with from and until
> parameters set, and we send back an incomplete list with a resumption
> token, then when the client submits a request using the resumption
> token, can we also expect them to supply again the from and until
> parameters?
>
> This affects what information we need to store about the request against
> the resumption token.
>
> Example:
>
> First request:
> http://some.where/oaipmh?verb=ListIdentifiers&from=2011-06-29T03:05:00Z&
> until=2011-06-30T03:05:00Z
>
> To which response includes resumptionToken abcdefgh
>
> Must the second request then be
>
> http://some.where/oaipmh?verb=ListIdentifiers&from=2011-06-29T03:05:00Z&
> until=2011-06-30T03:05:00Z&resumptionToken=abcdefgh
>
> OR is it legitimate for a client just to ask this:
>
> http://some.where?verb=ListIdentifiers&resumptionToken=abcdefgh
>
> Thanks for the tip.
>
> -------------------------------------
> Moray McConnachie
> Director of IT    +44 1865 261 600
> Oxford Analytica  http://www.oxan.com
>
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----
Michael L. Nelson mln at cs.odu.edu http://www.cs.odu.edu/~mln/
Dept of Computer Science, Old Dominion University, Norfolk VA 23529
+1 757 683 6393 +1 757 683 4900 (f)