Hi Tim, thanks for your prompt answer.

It's not really what i expected, to be more specific >

First, i have to harvest lot of data from multiple DB (remote or not) with, of course, different structures/models and format of datas ... sometimes no DB just flat CSV/xsl files...
That's why i use an IPT to create data mapping and to standardize the data stream into Dwc standard.
(I'm talking about millions of specimen)

Secondly, i build specific indexes of harvested data with a custom harvester using canadensys-harvester lib. ( Thanks to Christian). It's at this point that it's begin to be difficult with a denormalized view of the data from IPT Dwc-A.

 'Cause i need to transform this denormalized view or raw model into a normalize view that match with my big relational database model which become the new repository.

That's why i thought that the custom extensions could be make my life easier.

On Fri, Mar 14, 2014 at 4:32 PM, Tim Robertson [GBIF] <trobertson@gbif.org> wrote:

Hi Julien,

Thanks for your question.  It really depends on what you are trying to publish.  We can add extensions of course, but without knowing the specifics it is difficult to comment.

However, a “specimen, event, location” DB model would typically map to an Occurrence core with no extensions required - this is the most common use case of Darwin Core and the IPT.  An Occurrence core is basically a denormalized view of the data.

If I were the data manager, I would probably consider that I was publishing a “DwC Occurrence view” of my more complex model and as such would keep a view in the database along the lines of:

CREATE VIEW view_dwc_occurrence AS

SELECT

  specimen.bar_code AS occurrenceID,

  specimen.name AS scientificName,

  location.latitude AS decimalLatitude,

  location.longitude AS decimalLongitude,

  event.year AS year

FROM 

  specimen 

  JOIN event ON … 

  JOIN location ON …

WHERE

  <insert any conditions for record inclusion, such as non endangered etc>

Then in my IPT I would simply do “SELECT * FROM view_dwc_occurrence”.  Here you are flattening the normalised model into a denormalized DwC view of the data.

Maintaining a view in the database layer as opposed to a custom mapping in the IPT benefits you by:

  i) catching issues early with database schema changes since the DB will likely stop you with an error

  ii) offering an easy mapping of DB table field names, to DwC terms in a language I find very familiar (SQL)

  iii) a super simple IPT mapping, as all columns will map automatically in the IPT since they are DwC recognised terms already

Does that help in any way?  If not, could you please elaborate on the model and what you are trying to achieve and we’ll do all we can.

Thanks,

Tim

 

On 14 Mar 2014, at 16:06, Julien Husson <biology.info@gmail.com> wrote:

Hi,

I use Dwc-A to feed my BD.

We know the limits of the Dwc star schema to represent a relationnal database.

For example in the case of 1-n cardinality :  specimen --- event/record --- location.
If i understand the concept, I need to use the Darwin Core Occurrence extension, denormalize my relational model in a big raw model and transform / re-normalize this model to match with my DB model.

In order to reduce cost, dev and optimize sql statement, it will be grandly appreciate to add custom extension. In this case, i can to be very close of my relational database model and avoid multiple step of dev.

I discovered this link but explanantion is now deprecated
http://dag-endresen.blogspot.fr/2009/06/adding-extension-for-germplasm-to-gbif.html

Thanks,

J.

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