SODA-1_0-Err-1 < IVOA

---+ !Server-side Opertaion for Data Access version 1.0 Proposed Erratum 1: ID parameter UCD amendment

Author: Marco Molinaro

Date last changed: 2019-04-17

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---++ Rationale

!SODA protocol uses the *ID* parameter to specify opaque identifiers to the dataset or file to be accessed. The UCD specified in the !SODA-embedded 3-factor semantics is reported in the REC text as
<verbatim>meta.ref.url;meta.curation.SODA</verbatim>

This is not a valid UCD both for the, probably, typo of the added *.SODA* part and the fact that meta.curation identifies a *man/organization responsible for the data* as per the UCD vocabulary.

To remedy the situation we propose here to use *meta.id;meta.dataset* instead. This achieves:
   * typo amendment;
   * reference to a dataset rather than an organization;
   * using a UCD referring to an identifier rather than a resource locator;
   * keeping the identifier opaque as required by the specification.

---++ Erratum Content

This Erratum proposes to change, in §3.2.1 "*ID*" of [[http://ivoa.net/documents/SODA/20170517/index.html][SODA - Version 1.0]], the UCD in the sentence
<verbatim>
The UCD describing the ID parameter is meta.ref.url;meta.curation.SODA
</verbatim>

from

<verbatim>meta.ref.url;meta.curation.SODA</verbatim>

to

<verbatim>meta.id;meta.dataset</verbatim>.

---++ Impact Assessment

Being the UCD only used in !SODA to describe uniquely the *ID* parameter using the 3-factor semantics, this change will have a minimal impact on the service provider's side (requiring the UCD amendment and releasing it). 

On the client side, changing a UCD will break clients using 3-factor
semantics to find the parameter to pass the identifier in.
However, as ID is defined by both Datalink and SODA and no
competing definition ever existed, no known client actually uses
3-factor semantics to locate the ID parameter and instead just uses
the hard-coded name *ID*.  Hence, to our knowledge the UCD changed
here is ignored by clients, and no breakage will occur.  

The safety of changing this UCD is also plausible in view of the
fact that several data centers (e.g., GAVO's Heidelberg data
center; example [[http://dc.zah.uni-heidelberg.de/feros/q/sdl/dlmeta?ID=ivo%3A%2F%2Forg.gavo.dc%2F%7E%3Fferos%2Fdata%2Ff02891.fits][here]])
have been successfully operating SODA services that used
meta.id;meta.main as a UCD for *ID* without interoperabilty issues.

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Topic revision: r4 - 2019-04-17 - MarcoMolinaro