[timeDomain: model for Time series] discussion on Timeseries Data model Note / ND-point .... or not ??? !!!

[François Bonnarel]

Dear all,

This is a follow-up of these two emails

http://mail.ivoa.net/pipermail/dm/2017-July/005583.html

and

http://mail.ivoa.net/pipermail/dm/2017-July/005594.html

which are discussing chapter 4 of TimeSeries Data Model IVOA note within 
the scope of the TimeDomain effort summarized by Ada there:

http://mail.ivoa.net/pipermail/dm/2017-July/005581.html

Discussed issue:  do we need ND-points or not ?

Reference : Laurent's diagram in email 
(http://mail.ivoa.net/pipermail/dm/2017-July/005581.html) and CubeDM 
draft  from 
http://volute.g-vo.org/svn/trunk/projects/dm/CubeDM-1.0/doc/WD-CubeDM-1.0-20170203.pdf 
(last version)

In figure 4 of Jiri's note, SparseCube doesn't relate to the ND-point 
class as it is the case in the IVOA sparse cube data model project.

The ND-point class gathers several DataAxis (or Observable) containers 
for measurements on a given data Axis to represent a "point" or "event" 
in the data space.

On Jiri's figure a set of "CubeAxis" is directly related to 
"SparseCube". This doesn't imply explicitly a relationship between each 
of these "CubeAxis" instances and doesn't even imply that each of these 
"CubeAxis" will have the same number of instances.

So I am wondering if we should not reintroduce the ND-point feature 
between "SparseCube" and "CubeAxis" or "DataAxis". What do you think ?

François (after discussions with Laurent, Mireille and Ada on this topic)






Le 12/07/2017 à 10:57, Mireille Louys a écrit :
> Dear DM and Time Domain followers,
>
> I am trying, together with my CDS colleagues,  to recap on the various 
> DMs available in the IVOA and understand the possible links between 
> the future Time Series Model ( as sketched in Jiris's Note) and 
> existing DMs like ND-Cube and STC 2.
>
> Here is a graph proposed by Laurent Michel to clarify the links in 3 
> main parts :
>
>   * /DataSetMetadata DM/, which has the main ObsDataset Class ,
>   * /ND-CubeDM/, which defines a SparseCubedataset
>   * /TimeSerieCubeDM/, which highlights the special properties of a
>     Cube depending on a Time axis
>
> I think this is essential to highlight the inheritance path between 
> these 3 DM building blocks:
> a TimeSeriesCube  <is a >  NDCubeDM::SparseCubeDataset
> a NDCubeDM::SparseCubeDataset <is a > DatasetMetadaDM::ObsDataset
>
> ObsDataset has a /dataproduct//_//type/ attribute which allows to 
> discover all dataproducts of type ' timeseries'.
> this provides the container object for time-dependent data.
>
> If we need to select /timeseries dataproducts/ according to some 
> properties extracted from their data we can:
>  - reuse what Obscore DM provides to explain general axes properties
> target_name, s_region, s_resol, t_min, t_max, t_resol, em_min, em_max, 
> em_resol, etc. are the basic properties for discovery
>
> - provide a richer description of the TimeAxis and ObservableAxis.
> For that , extracting  a statistical profile from the data contained 
> in the Cube could do the job.
> this means to access and analyse the Data part in ND-Cube , i. e the 
> ND-Points gathered in a SparseCube Object
>
> I guess more properties can be exposed to qualify the axes present in 
> the Timeseries dataset , but for the moment , I see some overlap of 
> notions between
> CharacterisationDM::ObservableAxis,  STC2.0::CoordMeasurement (??) and 
> TimeSerieCubeDM::CubeAxis.
>
> This would be great if we could sort this out,
> but currently , I would appreciate your feedback on the attached 
> diagram , in order to proceed on the data model structure.
>
> Cheers, Mireille ( after discussions together with Laurent, François, 
> Ada)
>
> -- 
> --
> Mireille Louys
> CDS  						Laboratoire Icube
> Observatoire de Strasbourg	Telecom Physique Strasbourg
> 11 rue de l'Université 		300, Bd Sebastien Brandt CS 10413 		
> F- 67000-STRASBOURG			F-67412 ILLKIRCH Cedex
> tel: +33 3 68 85 24 34

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