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Setting-up an EPN-TAP service mean to publish a table in a DACHS server describing data we want to display. This table is referencing each file with a maximum amount of information by filling parameters defined by the standards of EPN TAP called epn core view . The EPN TAP standards has mandatory parameters wich can (except a few of them) be left empty and optional parameters, finally other columns could be defined by users to provide specific information. VESPA is a way to interrogate registered services published in different DaCHS servers using { keywords or ADQL queries}.

This tutorial will provide a very simple example to help beginners to understand how they can set up an EPN-TAP service. In this purpose, we will set up a service called "Planets" providing informations on the solar system planets.

For this example, we want to provide display these data on our service :

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First, a virtual machine hosting a DaCHS server must be setteled up. For simple services like this one, then metadata must be referrenced and a Comma Separated Values CSV file containing useful features must be created, other methods are available. Then a Ressource Descriptor written in XML must be written. This resource descritor will read the csv file and fill the table on DaCHS server. Finally, the service must be registered on VESPA portal (not for this tuto).

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In our example, each granule have the same type and correspond to one planet. There is no file to link for the granule, so no need to define a granule_uidSo, basically the granule_gid and granule_uid will be "Planet" and the name of the planet.


  • Define the epn_core parameters

Once granules are defined, you have to browse the EPN TAP V2 parameters and their description to see what could be informed. In order to define clearly the organization of the final table, it is advised to make fill a scheme with the EPN-TAP parameters on one side an what you decide to put into each in the other side available here in xls format. A large part of the mandatory parameters could be left empty, other parameters  you want to add could be defined as table columns.


  • Create a

    csv

    CSV file containing metadata

Metadatas which are varying from one granule to the other or cannot be post-treaded in the q.rd must be referenced in one column of a CSV file. The first row has to be the column's names, then each row will set the values for a granule. This CSV file will further be read by the resource descriptor to fill the tables in  DaCHS. You can use your favourite programming language to create this csv CSV file.

For this example, we give the link to the CSV, hand written CSV,  you can downolad it and the the  associated Resource Descriptor on github:

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