a high level language

[Tony Linde]

Hi Patrick,

> Our work at CADC and some of my past work has been in the 
> area of constraint systems. 

Do you have some refs?

Thanks,
Tony. 

> -----Original Message-----
> From: Patrick Dowler [mailto:patrick.dowler at nrc-cnrc.gc.ca] 
> Sent: 24 February 2003 20:37
> To: voql at ivoa.net
> Cc: Ed Shaya
> Subject: Re: a high level language
> 
> 
> On February 24, 2003 12:05, Ed Shaya wrote:
> >     I just want to reiterate that I think VOQL should be a 
> means for 
> > the
> >
> > astronomer to clearly specify what astronomical knowledge he/she 
> > wants.  It should not require the astronomer to know how 
> data is arranged at
> > each of the data centers, nor all of the steps required.   
> 
> This point cannot be over-emphasized. Storage data management 
> by services/institutions will vary alot and it must remain a 
> hidden implementation detail - with plenty of freedom on the 
> part of a service to implement in a suitable fashion.
> 
> >
> > The astronomer thinks "I am interested in objects with such 
> and such 
> > properties" and VOQL should allow a description of these 
> constraints,
> 
> With the ention of the word "constraints", I'll jump in here:
> 
> Our work at CADC and some of my past work has been in the 
> area of constraint systems. The great advantage of 
> constraint-based systems is that they do not, in the general 
> case, specify a query system per se. The same constraint 
> system can be applied as a query, a processing (typically
> filtering) step, a theorem-prover, etc. 
> 
> Since VOQL is still young, I suggest that instead of 
> inventing a "query language" we will be better servced by a 
> constraint toolkit. The advantages are many:
> 
> - easy to convert to a query
> - easy to apply as a processing or filtering step
> - easy to build a UI that allows users to construct 
> constraint systems since
>   constraints are "things" to be created and manipulated
> - easy (well, easier :-) validate
> 
> Although I don't go crazy for this sort of thing:
> 
> - easy to serialize as XML (constraints are things with 
> simple parent-child relations
>   between them and the expressions, operators, and constants in use)
> 
> My 2c (although I guess Canadians should up that to 3c),
> 
> 
> -- 
> Patrick Dowler
> Tel/Tél: (250) 363-6914 | Fax: (250) 363-0045
> Canadian Astronomy Data Centre    | Centre canadien de 
> donnees astronomiques
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> recherches Canada
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