[OAI-implementers] handling unavailable data

[herbert van de sompel]

Ben Henley wrote:
> 
>         Thanks for the help. Should a note about this point perhaps be added
> to the protocol?
> 


I will add it to our "to do" list.

Thanks for bringing this up.

herbert

> > -----Original Message-----
> > From: Hussein Suleman [mailto:hussein@vt.edu]
> > Sent: 29 March 2001 21:42
> > To: Ben Henley
> > Cc: 'oai-implementers@oaisrv.nsdl.cornell.edu'
> > Subject: Re: [OAI-implementers] handling unavailable data
> >
> >
> > hi
> >
> > i would think returning empty lists is not a good idea because the
> > service provider could make long-term assumptions based on
> > that - in the
> > case of ListMetadataFormats that there are none.
> >
> > my suggestion would be to use HTTP error codes to indicate that the
> > server cannot respond because of some internal problem ...
> > for example,
> > you could use "503 Service unavailable" and possibly return a
> > "retry-after" time, which supports  automatic harvesters quite nicely
> > (even the repository explorer will honor those) ... for
> > completeness, if
> > you want a really solid interface, you might consider using
> > some flavor
> > of upper-bounded exponential backoff so that the retry-after times
> > follow a 1,2,4,8,...,r sequence for subsequent requests while the
> > database is unavailable.
> >
> > hope this helps ...
> >
> > ttfn
> 
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-- 
Herbert Van de Sompel
Visiting Assistant Professor
Cornell University -- Computer Science
tel + 1 - 607 - 255 - 3085
fax + 1 - 607 - 255 - 4428
http://www.cs.cornell.edu/people/herbertv/
digital life in libraries used to be primitive