TimeSeries

[Doug Tody]

Also, in analogy with Spectrum, since we don't actually have a SED
model yet, and a time series is not a SED in any case, we might better
have something like "ts:TimeSeries.Data.FluxAxis" for the UTYPEs.

	- Doug


On Fri, 10 Aug 2007, Doug Tody wrote:

> Hi Francois -
> 
> > Notice that in the VOTABLE we considered the example as a SED with
> > two segments (one for each color). Although they are not listed in
> > the Spectrum Reference document we added the head element SED in
> > the utypes and replace Spectrum by TimeSeries everywhere. these new
> > utypes can be easily inferred from the xml schema in the general SED
> > case when segments are different from the single spectrum case.
> 
> For a time series with multiple flux values per time coordinate,
> why not represent this as a single segment?  Normally this would
> be a single observation, and all the other metadata is the same.
> I should think that multiple segments would be used for observations at
> different times, much as for a multi-segment spectrum, the different
> segments might represent different regions of spectral coordinate
> (e.g., as for an Echelle).
> 
> If we take a time series with multiple flux values per time sample,
> and serialize it in TSV, one would expect to see something like
> 
>     TimeValue   Flux1   FluxErr1   Flux2    FluxErr2
>     167.1178    5.105   0.162      5.617    0.080
>     181.0784    5.392   0.135      5.609    0.079
> 
> which would be the direct analogue of a VOTable representation which
> has mutliple flux values per time sample, and would be what we get
> if we write out this same time series in CSV/TSV instead of VOTable.
> 
> In this case the VOTable would contain multiple GROUPs with UTYPE
> spec:SED.TimeSeries.Data.FluxAxis, however I don't see any problem 
> with this.  For UTYPE the important thing is that the UTYPE uniquely
> identify the field of a data model; this does not mean that we cannot
> have multiple instances of a data model in a single namespace, such
> as a VOTable.
> 
> 	- Doug
>