ADQL v0.7.3

[Vivek Haridas]

The string form of ADQL defined by
the BNF (http://www.ivoa.net/internal/IVOA/IvoaVOQL/adql.ycc) is the
standard for ADQL.

The XML schema needs to be able to express any string in ADQL to
facilitate parsing.

I will soon post the steps taken to produce the XSD.

My opinion is that We should not attempt to alter SQL beyond making our
astronomy additions (Xmatch,region)

Hence, we should not change cardinality of operators in the XSD since this
can not be supported by SQL.

with Best Regards,
Vivek


On Mon, 1 Mar 2004, Tony Linde wrote:

> We don't seem to be getting far on the ADQL v0.7.3 discussions. My main
> concerns are about 'proving' the validity of the simplification and how we
> manage ADQL in the future.
>
> We need a clear statement of how the current v0.7.3 is generated (and also
> how v0.7.1 aka 0.8 was generated). It seems that a SQL-92 BNF - SELECT only
> - was put through some tool which created an xml schema version, BNF/x. This
> was then modified to add cross match and region capability, giving ADQL/x.
> This, effectively was the v0.7.1 version. This version was them 'simplified'
> by losing some of the common structures (eg Search type) and coalescing
> stacked elements into single ones; lets call this ADQL/sx.
>
> Is this a correct summary?
>
> If we're to standardise ADQL and we want the BNF to remain as the core, we
> need to document and/or automate each of these transitions. All of the /x
> --> /x transitions can be automated using XSLD, and the BNF --> BNF/x is
> automated using the tool.
>
> Could Wil or Vivek please provide us with:
> 1. what is the exact BNF used and where was it sourced and how modified?
> 1. what is the name/location of the tool used to convert the BNF to BNF/x?
> 2. what modifications were made to convert BNF/x --> ADQL/x?
> 3. what modifications to ADQL/x were made to produce the simplified version,
> ADQL/sx?
>
> It doesn't make sense to me to introduce the extensive changes in the ADQL/x
> --> ADQL/sx transition yet to say that changing the cardinality of
> intersection & union searches from 2 to 2..* is invalid.
>
> Another question is how we manage the string version of ADQL, ADQL/s. It
> should be a simple matter to convert a single instance of an ADQL/x query
> (ADQ/x) into string form (ADQ/s) using XSL. But, if people want to allow
> *direct entry* of the string version of ADQL and to parse ADQL/s then we
> will need some way of generating a new BNF that corresponds to the modified
> ADQL/x or ADQL/sx; this should be an automated method so that future
> extensions can be incorporated easily.
>
> Cheers,
> Tony.
>
> __
> Tony Linde
> Phone:  +44 (0)116 223 1292    Mobile: +44 (0)7753 603356
> Fax:    +44 (0)116 252 3311    Email:  ael at star.le.ac.uk
> Post:   Department of Physics & Astronomy,
>         University of Leicester
>         Leicester, UK   LE1 7RH
>
> Project Manager,            Director,
> AstroGrid                   Leicester e-Science Centre
> http://www.astrogrid.org    http://www.e-science.le.ac.uk/
>