DAL Working Group meeting in Cambridge

[Doug Tody]

Folks -

A list of reading materials and an updated agenda for the DAL working
group has been posted on the IVOA Wiki at

    http://www.ivoa.net/twiki/bin/view/IVOA/InterOpMay2003DAL

See you all in Cambridge next week.

	- Doug


On Thu, 1 May 2003, Doug Tody wrote:

> VO Data Access Layer (DAL) Working Group
> IVOA, Cambridge, UK  May 12-16 2003
> 
> 
> Hi Folks -
> 
> We will have the kick-off meeting of the IVOA Data Access Layer (DAL)
> working group on Monday May 12 at the IVOA Interoperability meeting in
> Cambridge.  The initial discussion will be followed by smaller breakout
> meetings throughout the week, with a wrap-up discussion in plenary session
> on Friday morning.
> 
> The primary purpose of the DAL working group will be to define, over the
> next year or so, the initial set of IVOA standards for VO science data
> access.  In the Cambridge meeting we will need to clarify the scope of our
> working group and develop a roadmap of our activities for the next year.
> This will include identifying what data access standards are needed, how
> these will interoperate with each other, and how these will integrate
> with the infrastructure being developed by the other working groups
> (registry, UCDs, data models, VOTable, etc.).  A special topic, possibly
> for a subgroup, will be to discuss what should be included in the second,
> "IVOA" version of the simple image access protocol due out this summer.
> 
> Our first item of business is to prepare an agenda for the meeting.
> ***Anyone who is interested in presenting any material at the meeting
> should contact the WG organizers immediately.***  Please contact either
> myself (dtody at nrao.edu) or Markus Dolensky (Markus.Dolensky at eso.org),
> who is helping to organize the working group.  We can't promise anything
> at this point about presentations (it will depend upon the final agenda
> and the time available) but we do want to benefit from our collective
> experiences in preparing these standards.  Suggestions for agenda items
> or topics are also welcome.
> 
> 	- Doug
> 
> 
> To help identify the areas where work is needed some thoughts on the
> scope of the VO data access layer follow.
> 
> 
> Scope of VO Data Access Layer
> 
> The scope of the VO Data Access Layer includes the services and protocols
> used to access remote science data via the VO, as well as the software
> used to implement data access services.  Ultimately this will include
> advanced capabilities such as data subsetting, data model mediation,
> and server-side analysis, i.e., for grid computing.  We must also include
> some client-side software to demonstrate an end-user analysis capability
> and perform end-to-end testing and integration.  Ultimately most analysis
> software will come from the user community, not from VO.  DAL builds upon
> and integrates other VO technology for metadata, data models, data formats,
> registries, and queries.
> 
> The science data dealt with by the DAL potentially includes all of the
> following:
> 
>     catalogs
>         e.g., object catalogs
> 
> 	Catalog analysis is a fundamental VO capability which is beyond
> 	the scope of mere data access, but at the DAL level catalog
> 	and image/spectra access are often performed together.
> 
>     images
>         e.g., 2D sky images
>     data cubes
>         e.g., 2D sky images with a spectral axis
>     spectra, SEDs
>         mainly 1D spectra
>         2D/longslit spectra? (maybe not right away)
>     time series
>         e.g., time-resolved photometry
>         spectrally-resolved light curves
>         synoptic imagery (e.g., all-sky camera, synoptic surveys)
> 
>     event list (photon counting) data
>     visibility data (interferometry)
> 
> The highest priority goes to object catalogs and 2D sky images, for which
> prototype data access services are already available.  Spectral data cubes
> are probably best treated as a general type of image.  Next in priority
> are spectra, especially simple 1D spectra; spectra are a high priority for
> the next phase of DAL development.  Time series data is less common but is
> similar to 1D spectra and could possibly benefit from a similar approach.
> It would be useful to integrate event list data and visibility data into
> the VO, although our expectation is that most VO users will be interested
> in images produced from such data rather than the original data (image
> generation may need to be on-the-fly since there is in general no one
> best way to produce images from event data or UV data).
> 
> The highest priority for IVOA data access standards is probably in the area
> of standard data access protocols - this is what we should emphasize in
> the first year.  Protocols are, or should be, implementation-independent
> and hence are one of these easiest software elements to standardize.
> As the VO software and infrastructure becomes more complicated it will
> become increasingly important to provide some reusable VO framework-level
> software to simplify the job of those putting up services or writing
> client-side applications.  Finally as we move to grid computing it will
> become necessary to dynamically deploy computational components on any
> grid-enabled computational resource.  For this to be feasible we will need
> some interoperability standards in the areas of computational frameworks
> and components.
> 
>