SSAmples

[Markus Dolensky]

Jonathan McDowell wrote:
 > Doug, Markus:
 >  I have updated and improved my VOTable example serialization,
 > see the 2004 Aug 5 draft in
 > http://hea-www.harvard.edu/~jcm/vo/docs/spec.html
 > I hope this is closer to what we need. I'm still working on
 > generating a real life set of examples from my quasar spectral archive.
 >  - Jonathan


Hello Doug and Jonathan,

A SSAmple file containing 3 segments (SED point, 1d Spectrum, time series) is 
on the Wiki:
http://www.ivoa.net/internal/IVOA/IvoaDAL/ssample1.xml

The actual values were made up or were taken from the example given in the 
Spectral DM draft. I'll look at an example from NED as a next step.

Jonathan:
I was almost done with this based on the previous DM version dated Aug. 5 and 
so my comments do not refer to today's update. I noticed that you've fixed a 
couple of things like the PARAM syntax already. Hence, simply ignore related 
obsolete comments.

Also, the new STC was not taken into account and I'm open to suggestions how to 
map it to VOTable speak. Nonetheless, there are a number of points that the 
sample should help to address in its current form (below).

Thank you for your input.

Greetings,
Markus


******************


I. Inconsistencies between DM V0.9 and SSA interface as of Boston in May
========================================================================

1. Target.CreationType values {Archival, Dynamic, Custom} in DM differ from
    SSA interface Sed.CreationType {Atlas, Virtual}. My sample sticks to the DM
    assuming that "Atlas" maps to "Archival" and "Virtual" to "Dynamic+Custom".
2. Target.pos exists in the DM only. Presumably this is the search position, 
whereas each segment has an actual pointing/object position?
3. SNR is in object "Derived" in the DM and not in "Target"
4. Flux.Npts is missing in the DM. We probably don't need it(?)
5. SpectralCoord.deReddened and SpectralCoord.correlated are missing; These 
things could go into a new object SpectralCoord.Quality or is this what 
CustomParams is about?
6. DM has a Location object in each Segment rather than a global one in the 
Target object. My SSAmple sticks to the DM.



II. Further Comments/Errata
===========================

a)
the value attribute of a PARAM element is supposed to contain the datum; hence 
the value attribute is mandatory; all PARAM elements need to be modified 
accordingly

b)
a vector can be expressed as a space separated list but not comma separated as 
in PARAM Coverage.Location.Sky

c)
GROUPing works differently: use PARAMref and FIELDref; all GROUP elements need 
to be modified accordingly

d)
in VOTable examples UCD words are colon separated instead of semicolon separated

e)
Coverage.Extent.Time is given as time.expo in table 5.1 and time.interval in 
the sample VOTable
One could allow both, of course: time.expo for the net exposure time and 
time.interval denotes the difference between start time of the first exposure 
and the end time of the last subexposure.

f)
Why are "Sky" and "Time" encoded as subGROUPs in object "Coverage.Location" 
instead of PARAM elements? In other words, why does Extent and Location have a 
different substructure although they are similarly defined in table 5.1?

g)
DataID.Date: append "Z" for UT to time string; according to ISO standard it's 
considered local time otherwise

h)
If Target is contained in the SED object then the utypes should be SED.Target.* 
instead of Target.*

i)
Was it intentional to define Target.VarAmpl (src.var.amplitude) as well as 
Derived.VarAmpl (stat.ampl)?

j)
How about defining Flux.Quality using the VALUES/OPTION element (see example)?
Given this encoding is there really a need for Flux.Quality.N with n={0,1, 
...}? Or, is the intention to combine quality flags? If so, how?

k)
We do lack suitable utypes for the TABLE element in order to define the type of 
Segment that follows: { Sed, Spectrum, TimeSeries }
"Spectrum" as the utype of the 1st table is ambiguous since the root object is 
SED in the DM diagram

l)
Does the percent "%" in %Contact and %Contact.Email have a particular meaning?
Can we remove the dot in Contact(.)Email ?

m)
More generally, how about removing dots in field names?
SED.Bandpass.Min => SED.BandpassMin
SED.Bandpass.Max => SED.BandpassMax

n)
The closing TR elements are missing in TABLEDATA of the DM sample

o)
replace "Barycentric" by 8-char tag "Barycent" in sample VOTable in the DM doc


III. Suggestions for assignment of UCDs
=======================================
SED.NSegments		  meta.number (instead of arith.factor)
SED.SegmentType	          meta.code
# move CreationType to DataID object, otherwise model and observational data 
cannot be combined in one VOTable doc.
SpectralCoord.deReddened  meta.code.qual
SpectralCoord.correlated  meta.code.qual
Spatial.Resolution	  instr.ang-res
Time.Accuracy.BinSize	  time.period

reference:
http://vizier.u-strasbg.fr/UCD/lists/ucd1p-words-20040520.txt