a high level language

[Tony Linde]

Hi Kirk,

Thanks for the reply.

> This query involves 
> multi-wavelength data and multi-modal data (catalogs, spectra), and 
> thereby the query must be parsed and distributed to 
> appropriate data centers and maybe the data need to be 
> shipped to some service (e.g., to generate line lists from 
> optical spectra). 

This is what I assumed from Ed & Brian's document and why I raised the
question. I can see that a *query* language might cover more than a
simple single-dataset query, eg selecting from a join of distributed
datasets with sub-selects etc. - the sort of thing you can do at the
moment using SQL on the more advanced databases (though without the
distributed bit).

However, when it comes to shipping intermediate data to another service
for analysis, reduction etc., I would consider this to be *workflow*,
requiring a separate description using a workflow language (as in the
commercial world with the recent development of BPEL4WS).

> VOQL is a standardized language to capture scientist's 
> queries to the distributed heterogeneous collections that 
> comprise the VO. 

There I would agree. But the VO comprises more than data services, it
includes functional services such as those to 'generate line lists'.
Pushing the results of a query to such services, or using the results of
a query in another, later, query amount to workflow construction.

There is a danger that, in trying to combine queries and workflow in a
single language, we will overcomplicate the matter and reduce the chance
of using or extending existing efforts in the development of query and
workflow languages.

Cheers,
Tony. 

> -----Original Message-----
> From: Kirk Borne [mailto:borne at rings.gsfc.nasa.gov] 
> Sent: 23 February 2003 22:01
> To: ael at star.le.ac.uk
> Cc: voql at ivoa.net
> Subject: Re: a high level language
> 
> ...