[Dachs-support] Two questions on datalinking
Yan Grange
grange at astron.nl
Thu Aug 26 14:57:09 CEST 2021
Heya
On 26/08/2021 09:17, Yannick Roehlly wrote:
> Hi all,
>
> Le jeudi 26 août 2021, 09:02:08 CEST Markus Demleitner a écrit :
>>> 2. The main download link of the data then. I think I have three choices
>>> (basically what I want to bind the path to). The dlmeta, the dlget or a
>>> direct link to the remote data set. I find it hard to understand how much
>>> of a difference that makes in practice and whether or not there should be
>>> a preference for using either. Will Aladin be able to handle dlmeta links
>>> more or less transparently for instance?
>> So, last time I checked the mainstream Aladin didn't handle datalink
>> all that smoothly, but it's been a while. Still, I'd see two basic
>> cases:
>>
>> smallish data (up to ~1e8 bytes these days): Just put in the
>> direct link. Datalink-aware clients will still find datalinks
>> because there's a descriptor block, and if you want, you can put in
>> an extra datalink column as described at the end of
>> http://docs.g-vo.org/DaCHS/ref.html#integrating-datalink-services so
>> even browsers can see datalinks.
>>
>> (b) largeish data (more than ~1e8 bytes these days): You probably
>> don't want to entice people to blindly download those, and so I'd
>> point to dlmeta. It'll not be immediately pretty, but when people
>> have to pull large amounts of data, it'll never be really pretty.
> I may add another use case here to the use of the datalink: to have
> homogeneous outputs; in particular for spectra.
>
> If you are serving spectra, using the datalink allows Topcat to plot them even
> if the spectra are stored as image FITS files. Also, you may have a
> collection of inhomogeneous spectra files (some as table, other as images with
> different formats) and using the datalink allows you to have every time the
> same answer.
Thanks Markus and Yannick! Very insightful. My first off the bat
reaction to the 1e8 limit would be "but we are radio! 1e8 is like...
Nothing". Our images are about 4.5 times that. So I need to decide how
stubborn I am by interpreting "~1e8" as an order of magnitude :). Maybe
pushing tooling to support data links is actually a good action on the
RadioIG since I cannot imagine this problem to be unique to our data
releases :).
As things go I have an unrelated question:
Right now our accrefs contain +-signs, so getdata URL will also contain
a + sign. I have noticed dachs to complain if I have +-es in file names.
Is there a way that people replace plusses in file names? I can not
immagine that we are the first ones to have this problem given general
source naming conventions in astronomy (on the Northern hemisphere) :).
>
> Yannick
>
--
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Yan Grange
SDC software developer
ASTRON
het Nederlands instituut voor radioastronomie
the Netherlands Institute for Radio Astronomy
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