[tdwg-tapir] Fwd: Tapir protocol - Harvest methods? [SEC=UNCLASSIFIED]

Markus Döring mdoering at gbif.org
Wed May 14 11:21:37 CEST 2008

Interesting that we all come to the same conclusions...
The trouble I had with just a simple flat csv file is repeating  
properties like multiple image urls. ABCD clients dont use ABCD just  
because its complex, but because they want to transport this  
relational data. We were considering 2 solutions to extending this csv  
approach. The first would be to have a single large denormalised csv  
file with many rows for the same record. It would require knowledge  
about the related entities though and could grow in size rapidly. The  
second idea which we think to adopt is allowing a single level of 1- 
many related entities. It is basically a "star" design with the core  
dwc table in the center and any number of extension tables around it.  
Each "table" aka csv file will have the record id as the first column,  
so the files can be related easily and it only needs a single  
identifier per record and not for the extension entities. This would  
give a lot of flexibility while keeping things pretty simple to deal  
with. It would even satisfy the ABCD needs as I havent yet seen anyone  
requiring 2 levels of related tables (other than lookup tables). Those  
extensions could even be a simple 1-1 relation, but would keep things  
semantically together just like a xml namespace. The darwin core  
extensions would be good for example.

So we could have a gzipped set of files, maybe with a simple metafile  
indicating the semantics of the columns for each file.
An example could look like this:

# darwincore.csv
102    Aster alpinus subsp. parviceps    ...
103    Polygala vulgaris    ...

# curatorial.csv
102    Kew Herbarium
103    Reading Herbarium

# identification.csv
102    2003-05-04    Karl Marx    Aster alpinus L.
102    2007-01-11    Mark Twain    Aster korshinskyi Tamamsch.
102    2007-09-13    Roger Hyam    Aster alpinus subsp. parviceps  
103    2001-02-21    Steve Bekow    Polygala vulgaris L.

I know this looks old fashioned, but it is just so simple and gives us  
so much flexibility.

On 14 May, 2008, at 24:39, Greg Whitbread wrote:

> We have used a very similar protocol to assemble the latest AVH cache.
> It should be noted that this is an as-well-as protocol that only works
> because we have an established semantic standard (hispid/abcd).
> greg
> trobertson at gbif.org wrote:
>> Hi All,
>> This is very interesting too me, as I came up with the same  
>> conclusion
>> while harvesting for GBIF.
>> As a "harvester of all records" it is best described with an example:
>> - Complete Inventory of ScientificNames: 7 minutes @ the limited 200
>> records per page
>> - Complete Harvesting of records:
>>  - 260,000 records
>>  - 9 hours harvesting duration
>>  - 500MB TAPIR+DwC XML returned (DwC 1.4 with geospatial and  
>> curatorial
>> extensions)
>> - Extraction of DwC records from harvested XML: <2 minutes
>>  - Resulting file size 32MB, Gzipped to <3MB
>> I spun hard drives for 9 hours, and took up bandwidth that is paid  
>> for, to
>> retrieve something that could have been generated provider side in  
>> minutes
>> and transferred in seconds (3MB).
>> I sent a proposal to TDWG last year termed "datamaps" which was
>> effectively what you are describing, and I based it on the Sitemaps
>> protocol, but I got nowhere with it.  With Markus, we are making more
>> progress and I have spoken with several GBIF data providers about a
>> proposed new standard for full dataset harvesting and it has been  
>> received
>> well.  So Markus and I have started a new proposal and have a  
>> working name
>> of 'Localised DwC Index' file generation (it is an index if you  
>> have more
>> than DwC data, and DwC is still standards compliant) which is  
>> really a
>> GZipped Tab file dump of the data, which is slightly extensible.  The
>> document is not ready to circulate yet but the benefits section reads
>> currently:
>> - Provider database load reduced, allowing it to serve real  
>> distributed
>> queries rather than "full datasource" harvesters
>> - Providers can choose to publish their index as it suits them,  
>> giving
>> control back to the provider
>> - Localised index generation can be built into tools not yet  
>> capable of
>> integrating with TDWG protocol networks such as GBIF
>> - Harvesters receive a full dataset view in one request, making it  
>> very
>> easy to determine what records are eligible for deletion
>> - It becomes very simple to write clients that consume entire  
>> datasets.
>> E.g. data cleansing tools that the provider can run:
>>  -  Give me ISO Country Codes for my dataset
>>     -  The application pulls down the providers index file,  
>> generates ISO
>> country code, returns a simple table using the providers own
>> identifier
>>  - Check my names for spelling mistakes
>>    - Application skims over the records and provides a list that  
>> are not
>> known to the application
>> - Providers such as UK NBN cannot serve 20 million records to the  
>> index using the existing protocols efficiently.
>>  - They have the ability to generate a localised index however
>> - Harvesters can very quickly build up searchable indexes and it is  
>> easy
>> to create large indices.
>>  - Node Portal can easily aggregate index data files
>> - true index to data, not an illusion of a cache. More like Google  
>> sitemaps
>> It is the ease at which one can offer tools to data providers that  
>> really
>> interests me.  The technical threshold required to produce services  
>> that
>> offer reporting tools on peoples data is really very low with this
>> mechanism.  This and the fact that large datasets will be  
>> harvestable - we
>> have even considered the likes of bit-torrent for the large ones  
>> although
>> I think this is overkill.
>> As a consumer therefore I fully support this move as a valuable  
>> addition
>> to the wrapper tools.
>> Cheers
>> Tim
>> (wrote the GBIF harvesting, and new to this list)
>>> Begin forwarded message:
>>>> From: "Aaron D. Steele" <eightysteele at gmail.com>
>>>> Date: 13 de mayo de 2008 22:40:09 GMT+02:00
>>>> To: tdwg-tapir at lists.tdwg.org
>>>> Cc: Aaron Steele <asteele at berkeley.edu>
>>>> Subject: Re: [tdwg-tapir] Tapir protocol - Harvest methods?
>>>> 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
>>>> process:
>>>> 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?
>>>> thanks,
>>>> aaron
>>>> 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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