VODax and VODMX

[Tony Linde]

Hi Jonathan,

As I said in the private email to you, feel free to dump VODMX if it crosses
across any aspect of DM - I tried to make it clear that it should not do so.
I've not followed the DM list discussions closely so was unaware from that
whether there were any active moves on developing xsd-based versions of the
Obs & Quantity models and I couldn't see anything on the web page that was
relevant. I only wanted something relevant that I could point to from the
VODaX page.

If you really want to see why I kicked off the VODaX effort, check out the
threads over the last couple of days in this list and on registry and arch.

Again, feel free to change the content of the VODMX page and/or the name of
the topic or even delete the whole thing but it'd be useful to have a set of
links to existing DM/xsd work in one place wherever you decide it ought to
be.

Cheers,
Tony.  

> -----Original Message-----
> From: owner-interop at eso.org [mailto:owner-interop at eso.org] On 
> Behalf Of Jonathan McDowell
> Sent: 20 May 2004 20:50
> To: ael at star.le.ac.uk; interop at ivoa.net
> Subject: Re: VODax and VODMX
> 
> 
> > Tony Linde wrote:
> 
> > In order to curtail the rancorous debates on VOTable, I've 
> taken Roy's 
> > suggestion and have set up an effort to develop a data model-based 
> > alternative to VOTable. I've tentatively titled it the 
> VODaX (Virtual 
> > Observatory Data eXchange) format and the start page on the 
> wiki for it is:
> >   http://www.ivoa.net/twiki/bin/view/IVOA/VODaX
> 
> Tony, I guess I'm a little puzzled by this since I think we 
> are already doing it.  I would have thought that the content 
> of VODaX is "Easy, we'll use schema-based XML to exchange 
> data" and the content of VODMX is addressed initially by the 
> serialization sections of the Quantity data model document, 
> and in general by the discussions on schema serializations 
> that have been going on for some time in the DM group.  We 
> have proposed XML serializations for Quantity, for Space-Time 
> Coords, and (at a tentative level) for Mapping, while a 
> proposal for Spectral Energy Distributions is circulating 
> within the DAL group SSAP effort and will be unveiled in the 
> next couple of days. We certainly need help developing these 
> and other serializations, and I would welcome your comments 
> on any of the existing proposals.
> 
> However, I am not convinced that the serialization effort 
> should be separated from the DM effort in the way that you 
> appear to suggest, because it is often hard to understand the 
> DM abstractions without serialization examples, so the design 
> loop is pretty tight.
> 
> My attitude to the serialization problem has been that
> 
> (1)  I expect to define a reference serialization for each 
> data model in XML schema, as has been stated by the DM group 
> in each of its WG meetings.
> 
> (2) I also expect VOTABLE serializations to be used, at least 
> for some data models, and the UTYPE effort is trying to 
> develop a standard way to do this.
> 
> (3) In at least some cases we may even define a reference 
> FITS serialization if that seems appropriate.
> 
> All of these are part of the existing DM effort. Perhaps 
> there is some content to your VODaX idea that I'm not 
> understanding - feel free to clarify. And I'm open to having 
> a separate twiki area for the XML schemas derived from the 
> data models, we can call it VODMX if you like, although we 
> should make the links to the corresponding models very clear.
> 
> In parallel with this is the contentious argument of when to 
> use VOTABLE and when to use object-specific schemas. I think 
> this is an argument we need to have, and the DM group is 
> certainly one legitimate place to have it. Ultimately I 
> believe the argument will be resolved only after 
> implementations - the two camps both have legitimate points 
> of view that reflect a fundamental division in the VO between 
> 'evolve current astronomy software and approaches so we can 
> interoperate' and 'use the latest software technology even if 
> it doesn't map well to how astronomers currently do things'. 
> As you imply, the solution for now is to let both camps 
> develop their standards. Yells of 'heretic!' and other 
> suggestions that one or other approach is fundamentally 
> flawed will continue to fall on deaf ears and will be 
> unproductive; better to work with people who agree on your 
> approach and develop that approach, than to spend your time 
> derailing others' efforts.
> 
> I don't know yet which approach will turn out to be most 
> practical, so I'm happy to work to push along both paths.
> 
>   - Jonathan
>