SODA Gripes (5) No single-value arguments for intervals

[Patrick Dowler]

That was an idea to make simple things simple to do. In parameter
descriptor terms it seems to be the difference between arraysize="2"
xtype="interval" (both bounds required) and arraysize="2*" xtype="interval"
(one or two values) which permits a scalar value...


In WD-DALI the section on intervals simply sys arraysize="2" and has no
text or examples with scalar values. It is my intention to find a
definitions (for all the xtypes defined in DALI) that can be used in SODA
and TAP.

Aside: I don't see anything in DALI that prevents uxing xtype="interval"
with all numeric types (floating point and integer), so I will make that
change in the next WD.

Personally, I'm not too attached to the single number means scalar value...
I agree it doesn't add any capability, but it might make a common mistake
do what was probably intended.

Pat


On 29 February 2016 at 02:29, Markus Demleitner <
msdemlei at ari.uni-heidelberg.de> wrote:

> Dear DAL,
>
> I trust you've all been looking forward to it: here's the next
> installement in the series on SODA gripes (but this one is short and
> relatively straightforward).
>
> This is about the following regulation in the current Draft
>
>   "If there is one single value the interval is assumed to be
>   infinitely small (a scalar value)."
>
> (e.g., on BAND, but it seems to be intended as a general rule).
> Essentially, by this rule,
>
> BAND=550
>
> would be equivalent to
>
> BAND=550 550
>
> I propose to strike this rule.
>
> It does not add new capabilities but is a significant pain in
> implementation, since you'll somehow have to teach your VOTable
> tabledata parser to suddenly accept a single value into a 2-array
> (and really, what should it put into the second element of that
> 2-array? NULL?  Please not, remember there's integers, too).
>
> And even if single values weren't a big pain:
>
> $ python -c "import this" | grep preferably
> There should be one-- and preferably only one --obvious way to do it.
>
> Cheers,
>
>            Markus
>
>
> For bookkeeping, here's the current state of my series of gripes,
> unnumbered means "you can still look forward to it".  The names in
> parenthesis in case of unresolved items are the persons that more or
> less promised to get back to these issues:
>
> (1) The big one (François)
> (2) No gratuitous xtypes (OK)
> (3) In-DAL SODA descriptor optional, introductory text (François)
> (4) Mandated multiplicities considered harmful (Pat)
> (5) No single-value arguments for intervals (everyone)
> () @value and @ref semantics documented for PARAMs
> () Spatial coverage discovery and the RA and DEC parameters
> () Pixel coutouts: PIXEL_n
> () Behaviour for no-ID queries?  For queries with only ID?
> () POS doesn't have an xtype
> () Examples stuff: example example, and perhaps a dl-id term?
>
>


-- 
Patrick Dowler
Canadian Astronomy Data Centre
Victoria, BC, Canada
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