<div dir="ltr"><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">I think with the addition of xtype here this isn't just a plain old array. With circle and polygon params we give just a MAX (minimum spanning circle and polygon boundary respectively), so when collapsing this to 1-d I agree that it probably should have been a MAX interval (bounds, just like polygon).</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">So, in my view the example (and my datalink service that generates these) is wrong; a human can grok the meaning but it's inconsistent with other datalink examples/output.</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">If we can reach an agreement, I am willing to write an errata for the example, fix/clarify this in WD-DataLink-1.1, and fix my buggy service :-)</div><div class="gmail_default" style="font-size:small"><br clear="all"></div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div>--<br></div><div>Patrick Dowler<br></div>Canadian Astronomy Data Centre<br></div>Victoria, BC, Canada<br></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, 4 Oct 2022 at 03:56, Markus Demleitner <<a href="mailto:msdemlei@ari.uni-heidelberg.de">msdemlei@ari.uni-heidelberg.de</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Adrian,<br>
<br>
On Mon, Sep 26, 2022 at 07:53:14PM +0000, Damian, Adrian wrote:<br>
> <PARAM arraysize="2" datatype="double" name="BAND"<br>
> ucd="em.wl" unit="m" value=""<br>
> xtype="interval"><br>
> <DESCRIPTION>Spectral cutout interval</DESCRIPTION><br>
> <VALUES><br>
> <MIN value="3.52631986e-07"/><br>
> <MAX value="9.21500998e-07"/><br>
> </VALUES><br>
> </PARAM><br>
> <br>
> The VOTable parser in astropy does not like the syntax - it<br>
> expects, and I would say logically so, that MIN and MAX have the<br>
> type of the BAND param, i.e. an interval. Is there a reason not to<br>
> have the above MIN and MAX expressed as the maximum interval, i.e.<br>
> <MAX value="3.52631986e-07 9.21500998e-07”/>?<br>
<br>
Well, this has always been a very sore spot (previously:<br>
<a href="http://mail.ivoa.net/pipermail/dal/2020-April/008330.html" rel="noreferrer" target="_blank">http://mail.ivoa.net/pipermail/dal/2020-April/008330.html</a>) -- and I<br>
think it needs to be discussed over on Apps, as it is really a<br>
VOTable problem.<br>
<br>
The meaning of MIN and MAX with arrays has never been properly<br>
defined. Now, given that arrays are supposed to be "homogeneous"<br>
data structures -- all members "mean" about the same thing --, one<br>
can argue that arraysize should be ignored for MIN and MAX, i.e.,<br>
that they are always scalar. I think that would certainly be the<br>
intent for OPTIONS and for VALUES/null (the latter of which is<br>
admittedly deprecated).<br>
<br>
Also, one cannot order vectors (respecting arithmetic); hence, a<br>
really well-defined MIN and MAX for arrays is not possible anyway.<br>
<br>
On the other hand, having component-wise MIN and MAX is of course<br>
possible (although that would have about as silly consequences of<br>
char arrays as the "ignore arraysize" convention). But even then one<br>
would have to ask what such a multi-component MIN/MAX would mean with<br>
arraysize="*".<br>
<br>
This latter interpretation is what we introduced in soda (against my<br>
mild resistence, if I may say so,<br>
<a href="http://mail.ivoa.net/pipermail/dal/2016-November/007633.html" rel="noreferrer" target="_blank">http://mail.ivoa.net/pipermail/dal/2016-November/007633.html</a>).<br>
<br>
Well -- I'd say it's time to clarify this whole thing in VOTable.<br>
I'd kind of like the "give up to arraysize elements; when fewer<br>
values are specified in MIN/MAX than are in the array, the last value<br>
is repeated" I had proposed in April 2020, I must say on re-reading<br>
it. This would help with the variable-length arrays and would indeed<br>
redeem the datalink example above. Of course, it's a bit painful in<br>
implementation, but perhaps not overly so.<br>
<br>
Whatever we go for: someone would have to put it (and something on<br>
OPTIONS and VALUES/@null) into the VOTable spec. I'd help out with<br>
it, but I don't want to push it along...<br>
<br>
-- Markus<br>
</blockquote></div>