SimpleDALRegExt1.2 Proposed Recommendation: Request for Comments

The latest version of SimpleDALRegExt 1.2 can be found at:

While future versions may be migrated elsewhere, VODataService 1.2 is managed by the legacy volute repository at:


SimpleDALRegExt defines a group of registry extensions for describing related "Simple" DAL services: Cone, Image, Spectra, etc. Occasional tweaks to vocabularies and incremental changes to the services' own standards are tracked here to keep potential registry search results in line with actual service capabilities, and to show connections between resources in new ways: in this case, adding auxiliary capability descriptions (see below.)

Changes since 1.1

Most of the document is unmodified. Some vocabulary cruft has been removed and tested with searches across all current registries to assure backward compatibility.

There are two changes which should be reviewed:

  • Section 4, the auxiliary capabilities. Introducing these has been the original motivation for building SRE 1.2.
  • SSAP services can declare which reference frames they support in POS. So far, there has been a list of those in the schema. We now point to a vocabulary developed in the run-up to MCT, Accepting this as REC would also make this vocabulary accepted.

Reference Interoperable Implementations

The auxiliary capabilities for the S-Protocols are a consequence of the Endorsed Note on discovering data collections. Compared to TAP auxiliary capabilities, they have not been used much yet (there are ivo://org.gavo.dc/lensunion/q/im and ivo://org.gavo.dc/hppunion/q/im, though). Hence, to our knowledge there is no client takeup of them. Consider this change editorial in nature; the standards identifiers from discovering data collections simply needed to be mentioned in this spec.

Similarly, using a vocabulary for the reference frames rather than an in-schema list is just intended to cut down on the number of lists of reference frames in the various standards. It has no operational implications (even less so since to date few services or clients actually offer different reference systems in SSAP queries).

Comments from the IVOA Community during RFC/TCG review period: 2021-03-01 to 2021-11-15

The comments from the TCG members during the RFC/TCG review should be included in the next section.

In order to add a comment to the document, please edit this page and add your comment to the list below in the format used for the example (include your Wiki Name so that authors can contact you for further information). When the author(s) of the document have considered the comment, they will provide a response after the comment.

Additional discussion about any of the comments or responses can be conducted on the WG mailing list. However, please be sure to enter your initial comments here for full consideration in any future revisions of this document

Comments from TCG member during the RFC/TCG Review Period: 2021-03-01 to 2021-11-15

WG chairs or vice chairs must read the Document, provide comments if any (including on topics not directly linked to the Group matters) or indicate that they have no comment.

IG chairs or vice chairs are also encouraged to do the same, althought their inputs are not compulsory.

TCG Chair & Vice Chair

Applications Working Group

Approved. These changes seem straightforward and likely to improve the data discovery experience. I have no significant concerns from an Application perspective.

-- TomDonaldson - 2021-10-25

Data Access Layer Working Group

Data Model Working Group

Grid & Web Services Working Group

Registry Working Group

Approved with product type removed and backward-compatibility checked. The refframe vocabulary itself looks good to me based on work with institutional holdings, further comments from astronomers and engineers with a wider background welcome. -- TheresaDower - 2021-11-11

Semantics Working Group

This document points to two vocabularies : product type ( and refframe (, which are still not approved. This can't go forward until refframe and product-type are fixed.

  • Right. Product type will be a topic at the Spring 2021 interop. Refframe... well, I'd be happy if someone else felt responsible for it. But yes, at least as long no other standard takes up refframe and gets it approved, this RFC is about refframe, too, and this can't go on unless we figure out what to do with the ancient VOTable terms. -- MarkusDemleitner - 2021-05-06

Data Curation & Preservation Interest Group

Education Interest Group

Knowledge Discovery Interest Group

Solar System Interest Group

Theory Interest Group

Time Domain Interest Group


Yes, it looks OK. I made a few comments of a mostly trivial nature which Markus addressed. Only one worth recording here:

  • Sec 3.1.4: I don't understand the business about specifying the catalogue in the test query, since this term doesn't appear in SCS itself. No doubt this is a hangover from some long-standing wrinkles in SCS which we don't want to mess with now, but maybe a couple of words of explanation would be in order?
    • [Markus]: Hm... Frankly, I'm not sure what to write... I'd say if it hasn't bothered anyone so far, we can let it sit until we've worked out how we'd like to do this in the next version of SCS.
-- MarkTaylor - 2021-03-16

Standards and Processes Committee

TCG Vote : Vote_start_date - Vote_end_date

If you have minor comments (typos) on the last version of the document please indicate it in the Comments column of the table and post them in the TCG comments section above with the date.

Group Yes No Abstain Comments
Apps *      
Registry *      
Ops *      
Topic revision: r7 - 2021-11-11 - TheresaDower
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