[tdwg-tapir] Tapir protocol - Harvest methods?

Aaron D. Steele eightysteele at gmail.com
Tue May 13 22:40:09 CEST 2008

at berkeley we've recently prototyped a simple php program that uses
an existing tapirlink installation to periodically dump tapir
resources into a csv file. the solution is totally generic and can
dump darwin core (and technically abcd schema, although it's currently
untested). the resulting csv files are zip archived and made
accessible using a web service. it's a simple approach that has proven
to be, at least internally, quite reliable and useful.

for example, several of our caching applications use the web service
to harvest csv data from tapirlink resources using the following
1) download latest csv dump for a resource using the web service.
2) flush all locally cached records for the resource.
3) bulk load the latest csv data into the cache.

in this way, cached data are always synchronized with the resource and
there's no need to track new, deleted, or changed records. as an
aside, each time these cached data are queried by the caching
application or selected in the user interface, log-only search
requests are sent back to the resource.

after discussion with renato giovanni and john wieczorek, we've
decided that merging this functionality into the tapirlink codebase
would benefit the broader community. csv generation support would be
declared through capabilities. although incremental harvesting
wouldn't be immediately implemented, we could certainly extend the
service to include it later.

i'd like to pause here to gauge the consensus, thoughts, concerns, and
ideas of others. anyone?


2008/5/5 Kevin Richards <RichardsK at landcareresearch.co.nz>:
> I think I agree here.
> The harvesting "procedure" is really defined outside the Tapir protocol, is
> it not?  So it is really an agreement between the harvester and the
> harvestees.
> So what is really needed here is the standard procedure for maintaining a
> "harvestable" dataset and the standard procedure for harvesting that
> dataset.
> We have a general rule at Landcare, that we never delete records in our
> datasets - they are either deprecated in favour of another record, and so
> the resolution of that record would point to the new record, or the are set
> to a state of "deleted", but are still kept in the dataset, and can be
> resolved (which would indicate a state of deleted).
> Kevin
> >>> "Renato De Giovanni" <renato at cria.org.br> 6/05/2008 7:33 a.m. >>>
> Hi Markus,
> I would suggest creating new concepts for incremental harvesting,
> either in the data standards themselves or in some new extension. In
> the case of TAPIR, GBIF could easily check the mapped concepts before
> deciding between incremental or full harvesting.
> Actually it could be just one new concept such as "recordStatus" or
> "deletionFlag". Or perhaps you could also want to create your own
> definition for dateLastModified indicating which set of concepts
> should be considered to see if something has changed or not, but I
> guess this level of granularity would be difficult to be supported.
> Regards,
> --
> Renato
> On 5 May 2008 at 11:24, Markus Döring wrote:
> > Phil,
> > incremental harvesting is not implemented on the GBIF side as far as I
> > am aware. And I dont think that will be a simple thing to implement on
> > the current system. Also, even if we can detect only the changed
> > records since the last harevesting via dateLastModified we still have
> > no information about deletions. We could have an arrangement saying
> > that you keep deleted records as empty records with just the ID and
> > nothing else (I vaguely remember LSIDs were supposed to work like this
> > too). But that also needs to be supported on your side then, never
> > entirely removing any record. I will have a discussion with the others
> > at GBIF about that.
> >
> > Markus
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