SODA-1_0-Err-1 < IVOA

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

Author: Marco Molinaro

Date last changed: 2019-04-18

<!-- Date accepted|rejected: 20NN-MM-DD -->

---++ Rationale

The [[http://ivoa.net/documents/SODA/20170517/index.html][SODA (version 1.0)]] protocol uses the *ID* parameter to specify opaque identifiers to the dataset or file to be accessed.

Three-factor semantics (Name, UCD, Unit) was meanly thought for interpretation of custom parameters in service descriptors. In the case of a parameter part of a standard, like the above !SODA *ID*, the definition of the parameter is unambiguous. However a 3-factor description is still useful for homegeneity and comparison to other parameters.

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 the following changes.

---++++ ID description

In [[http://ivoa.net/documents/SODA/20170517/REC-SODA-1.0.html#tth_sEc3.2.1][§3.2.1 "*ID*"]] of !SODA-1.0, update 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>

---++++ Three-factor tables

In [[http://ivoa.net/documents/SODA/20170517/REC-SODA-1.0.html#tth_sEc3.5][§3.5 "*Three-Factor Semantics*"]] change the UCD value for the ID parameter in *Tables 3 & 4* from from
<verbatim>meta.ref.url;meta.curation</verbatim>

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

---++++ SODA sync service descriptor example

In the *example* in [[http://ivoa.net/documents/SODA/20170517/REC-SODA-1.0.html#tth_sEc4][§4 "*Integration of Service Capabilities*"]] change the ID PARAM from
<verbatim>
<PARAM name="ID" 
                ucd="meta.ref.url;meta.curation" 
                ref="idcolumn-ref" 
                datatype="char" arraysize="*" value="" >
    <DESCRIPTION>The publisher DID of the dataset of interest</DESCRIPTION>
</PARAM>
</verbatim>

to
<verbatim>
<PARAM name="ID" 
                ucd="meta.id;meta.dataset" 
                ref="idcolumn-ref" 
                datatype="char" arraysize="*" value="" >
    <DESCRIPTION>The publisher DID of the dataset of interest</DESCRIPTION>
</PARAM>
</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: r6 - 2019-05-07 - PatrickDowler