VOTable 1.5 Working Draft (2023-09-13)

[Francois Ochsenbein]

Hello to everybody,

Being among the list of authors, I feel concerned by the evolution of the
VOTable standard, and would like to comment on the proposed changes for the
version 1.5.

Assigning to the COOSYS element the role of a GROUP is not a good idea, as
already pointed out by in the discussions by François Bonnarel.  An
accurate definition of which coordinates are given in the table is
certainly essential in order to enable meaningful correlations between
tables and cross-matching — and the COOSYS element was originally defined
as a component of a DEFINITIONS element for this purpose. I understand it
is useful to enumerate the components of a position and of its derivatives,
but that's exactly why the GROUP was created.

The relation between COOSYS and the FIELDs concerned by this definition is
of "1 to n" type — one system and several components; it is not safe to
permit a definition of this relation in both directions, as pointed out by
Pierre Fernique. The safe way of doing this in a relational model is to
insert the reference (foreign key) in each of the n components,
not the other way.

Several groups of positions may moreover exist in the table: for example in
a list of clusters, two barycenters are given, one from what was detected
in the optical, and a second from radio detections, and both positions are
(hopefully!) given in the same coordinate system. The enumeration of the
FIELDs giving both positions within the COOSYS would be quite confusing,
and a complete relationhip within the COOSYS would require a GROUP or
something similar to specify which RA and Dec must be associated.

I'm quite happy with the other changes — just be sure to keep the
consistency in section 7 (View of the schema, e.g. adding the refposition
attribute in the COOSYS element), and Appendix B (the schema itself) with
the final document.

Thank you for letting me participate in the discussion !

With my best wishes to everybody,

François Ochsenbein

==> On 2023-09-14 12:41+0000,
    Tom Donaldson <tdonaldson at stsci.edu> wrote:

>Dear VOTable Enthusiasts,
>
>On behalf of the Applications Working Group I’m pleased to announce
>the first Working Draft for VOTable version 1.5.  The document can be
>found here:  https://www.ivoa.net/documents/VOTable/20230913/
>
>
>Summary of changes since version 1.4
>--------------------------------------------------
>
>- Schema changes:
>--- COOSYS now has a refposition attribute analogous to TIMESYS
>--- COOSYS system now uses vocabularies
>--- ** COOSYS now allows FIELDref and PARAMref children for the
>specific purpose of building propagatable positions
>
>- Clarifications/rewording on:
>--- meaning of MIN/MAX value attributes for array types.
>--- removing the "recommendation" to use xmlns to do utype prefix
>binding. --- timescales for calendar epochs
>--- ID/ref positioning advice
>
>** - The COOSYS changes to handle propagation of positions are the
>most substantial proposed changes in this release.  For additional
>information, see:
>- Discussion in the PR:  https://github.com/ivoa-std/VOTable/pull/40
>- Draft PR in Astropy showing how this could be used:
>https://github.com/astropy/astropy/pull/14992
>
>The changes since version 1.4 were all made via Github pull requests.
>Some of these PRs contain useful discussion of the details so can be a
>useful reference for the ongoing Working Draft discussion.  The
>complete list of PRs included in this working draft can be found here:
>
https://github.com/ivoa-std/VOTable/pulls?q=is%3Apr+is%3Aclosed+milestone%3Av1.5
>
>
>Review and Comment
>-----------------------------
>
>Our job now is to review the document and propose/implement any
>changes needed.  The primary forum for discussion will be the
>Applications WG mailing list (apps at ivoa.net).  Github Pull Requests
>and Issues also offer a nice interface for discussion, so I recommend
>using those for discussing concrete or specific change proposals.  For
>example, instead of commenting on the mailing list that a particular
>paragraph should be different, submitting a Pull Request with the
>specific change in context can be a productive way to further the
>conversation.  If you have concrete proposals and would like help with
>creating a PR, just let us know on the Apps list and one of the
>editors will be happy to help.
>
>Note that as new PRs are merged into the master branch, a preview PDF
>is available at
>
https://github.com/ivoa-std/VOTable/releases/download/auto-pdf-preview/VOTable-draft.pdf
>   (also via the icon/badge at the top of the VOTable github repo
> README https://github.com/ivoa-std/VOTable#readme).
>
>
>Known Open Issues
>-------------------------
>
>We're maintaining the list of known issues in Github.  This is the
>complete list of known issues that could still be addressed in version
>1.5:
>
https://github.com/ivoa-std/VOTable/issues?q=is%3Aopen+is%3Aissue+milestone%3Av1.5
>
>Of those, only 2 are "must do" so have a label of "Priority: High":
>- Update sections 7.1 and 7.2 to match schema changes for COOSYS
>(https://github.com/ivoa-std/VOTable/issues/41)
>- Update the change log - section 9.4 (Differences Between Versions
>1.4 and 1.5, https://github.com/ivoa-std/VOTable/issues/46)
>
>
>
>Please review this Working Draft at your earliest opportunity.  I look
>forward to the discussion and suggestions on apps at ivoa.net as well as
>concrete proposals in Pull Requests (or new Github issues).
>
>Best regards,
>Tom
>
>
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