roadmap 2010-2011

[Douglas Tody]

On Fri, 10 Sep 2010, Patrick Dowler wrote:

> In the recent past we have had success in bringing more complex standards to
> completion by breaking them down into manageable pieces and re-using existing
> standards wherever possible. I would like to continue with this approach and
> propose the following as a way forward. Obviously there are many things to
> collectively consider and decide
>
> 1. remove all query parameters from SIAv2 and actively work on PQL

As has been noted previously, type typed DAL services support actual
data access (generation of virtual data), not just discovery (unlike
ObsTAP for example which is a pure discovery/description interface).
A generic PQL interface cannot support virtual data generation since
this requires knowledge of the type of data being access.  Hence,
PQL cannot replace the typed parameters in the DAL interfaces - this
is fundamental in my opinion.  If all we want to do is data discovery
and whole file data retrieval, then ObsTAP can be used instead of
the typed data access interfaces.

> 2. extract the "data linking" from SIAv2 and develop it as an independent
> standard that can be used in multiple services

I am not sure what this refers to, but I agree that data linking is a 
broader topic.

> 3. extract non-query parameters, error handling, VOTable usage, etc from SIAv2
> and develop it as a base standard for all DAL services; this standard would be
> called Data Access Layer Interface, or DALI :-)

Agree that this should be standardized, so far as possible, across
all the DAL interfaces.  It could possibly be extracted into a
separate document.  The question is whether there is enough here to
warrant this, as it would mean that service implementors and client
application folks have more documents to read.  I think this needs
more careful consideration.

> 4. pass work on the ImageDM to the DM-WG

There is no formal image data model for VO that I am aware of
(unlike spectra for example).  At present we use a combination of
FITS WCS and the Characterization model from DM.  I agree that if a
more formal image data model is needed this should be a DM activity,
it is just not clear that we are to that point yet, since FITS + Char
(with appropriate application detail in the SIAV2 spec) would appear
to provide all we need at present.

 	- Doug