DataLink inputParam PARAM/@value

Margarida Castro Neves mcneves at
Wed Nov 15 16:02:46 CET 2017


> On 14 Nov 2017, at 17:28, Mark Taylor <m.b.taylor at> wrote:
> Hi DAL,
> I'm taking my first thorough look at DataLink with a view to writing
> a client.  It mostly makes sense, but I have a question about the
> use of the PARAM elements in the inputParams GROUP within a
> service descriptor RESOURCE.
> According to VOTable, PARAM elements must have a @value attribute.
> But the @value doesn't seem to serve any purpose in an inputParams
> GROUP, since the PARAM is just there to describe arguments that
> are to be supplied, in some other way, to the described service.
> Is the idea that (in both the ref-to-column and no-ref cases)
> services must just fill in any syntactically legal value for the
> @value attribute, and that clients should ignore that value altogether?
> As far as I can see this is not mentioned in the DataLink document.
> Can one of the authors or some other DataLink expert comment?

I’m working on SPLAT’s Datalink code right now.
I don’t remember seeing any case where the value is not empty My code reads it and
(if not empty) would add it as a default value to the GUI, where the user can modify it.

> One other point: at the end of Section 4.3, it says
>   'This PARAM would be added to the GROUP name="input" of the service
>    description.'
> I think that should read 'name="inputParams"' - is that right?

I think so.


Margarida Castro Neves

German Astrophysical Virtual Observatory (GAVO)
Astronomisches Rechen-Institut (ARI)
Zentrum für Astronomie, Universität Heidelberg  (ZAH)
Mönchhofstr. 12 - 14, 69120 Heidelberg
phone +49-6221-54-1891   fax +49-6221-54-1888
mcneves at

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