Expressing 2- and 3-D coordinates

[Ed Shaya]

Rob Seaman wrote:

> I was hoping to ignore this conversation, oh well.
>
> I question the assertion that there has been "trouble" with the STC  
> specification - just the normal back and forth with any standard  
> format or interface as it faces different stakeholders.  Arnold was  
> responsive to our needs (basically for general targeting coordinates,  
> not just RA and Dec) by producing the STCLite schema.  I gather you  
> guys vetoed STCLite.  Really don't want to have the discussion to  
> figure out if that is your mandate.  In any event, we (the VOEvent  
> WG) have revisited the issue and have made one little suggestion - a  
> suggestion that it appears other folks have previously made.  Would  
> expect the discussion to continue until a consensus is formed.
>
> It is a VO-wide issue, not specific to VOEvent, to assert a  
> preference for schemata that are widely supported by parsers in the  
> field.
>
Part of the problem with xs:list and some other schema items is that 
processing requires XPath2.  Xpath1was developed before Schema and so 
does not know anything about any schema item that is not also DTD.  
Xpath2 is now a Candidate Recommendation scheduled to be a 
Recommendation around Feb 28.  So we happen to be at a time where to 
benefit from schema work you need to use extensions to standard 
processors.  But in 3 months time the extensions will become the 
standards.  Meanwhile, validation of things like xs:list are working 
fine for schema aware parsers.  Atomization takes place in 
downprocessing like XSLT which usually are not schema aware in the first 
place (excepting Saxon.SA).

> Question whether "archival ingest, registry, retrieval, and query"  
> cover all the bases of the VO.  Strongly agree with Alasdair that  
> VOEvent will be an important facility of the VO as well as of the  
> broader astronomical community - it's more than just "having  
> Institution A alert Institution B that it saw something".  Question  
> the wisdom of freezing the scope of the VO before the VO acquires a  
> user base.  Didn't think "virtual" was intended to apply to its user  
> community.

The VO user base includes everyone.  But the VO project space can not 
include all projects.

>
>> The VO should provide a fairly exacting set of scientific  
>> standards.  Projects  are free to  create copies  of the schema  and  
>> knock out  parts and change required  elements to  optional   ones.
>
>
> Suspect I'm not the only one to question the wisdom of this point of  
> view.  Is this free-for-all really preferable to having just two  
> standard choices of STC and a simplified STCLite?  For an important  
> facility such as STC, it is quite reasonable to expect multiple  
> stakeholders such as VOEvent to influence the development of a common  
> standard.  Suggest this would be simplified in the future were a  
> User's Guide to STC available.
>
It would be great if two STC schema is all everyone ever needs.  But if 
you accept STCLite then you accept the wisdom of the view.  STCLite is 
STC with elements knocked out to satisfy a specific project.   And that 
is fine.  Some projects are going to knock out a few more things some, a 
few less, some will add somethings of their own.

> Rob
> seaman at noao.edu