Common SIAP-2.0-Next and DAP1.0 page.

  • Previous material before May 2020 (most of it common with SODA-Next)
Old "DAL future" page :

IVOA note :

IVOA interop meetings presentation :

Paris :

College Park :

Victoria :

  • Additional material since May 2020 (IVOA interop meetings and Running meetings - most of it common with SODA-Next)

We list presentations also look at Notes and discussions.

May 2020 virtual interop :

November 2020 virtual interop :

January 2021 running meeting #7:

February 2021 running meeting #8 :

March 2021 running meeting #9 :

May 2021 virtual interop :

November 2021 virtual interop :

April 2022 virtual interop :

September 2022 running meeting #14 :

October 2022 virtual interop :

March 2022 running meeting #15 :

May 2023 Bologna interop :

November 2023 Tucson interop:

SIAP-2.0 feedback, issues and proposals (status in May 2020)

On GitHub:

Several SIAP2.0 parameters have a limited list of possible values – Some have lists limited by protocol (and obscore)

POL (Stokes, LINEAR, etc..) DPTYPE (image, cube, visibility, timeseries ;..) CALIB : levels FORMAT : fts, jpeg , png, etc..

– Some have free string values


– PARAMETERs less useful if we have no prior idea of their possible values. It often happens that services do not provide these lists of parameters although section 2.1.1 However Section 2.1.20 of SIAP2.0 states : Service PARAMETER self description Any service may include a DataLink service descriptor in the vOTable output to describe itself. this descriptor would describe the supported query parameters (standard and custom) including list of values for those with a fixed list (eg. COLLECTION INSTRUMENT FACILITY DPTYPE CALIB and FORMAT) *

This will allow to discover "possibilities" of the service prior to usage and optimize the queries

The "MAY" is obviously too weak. Version 2.1 could state SHOULD or MUST

Text change proposed in SIA Pull request #23 . Result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

ObsCore has an optional parameter "obs_release_date", but some projects complain no SIA PARAMETER allows to select on this.

Solution : create an OPTIONAL parameter to select on that ? What is the policy for OPTIONAL parameters ?

Done with SIA Pull request #16 . Merged in may 2022. (FrancoisBonnarel - 2023-05-31)

SIAP2 PyVO interface developers and CADC complain that no wild-carding or incomplete strong value can be admitted in string parameter. Only exact matching.

What is the price to pay to add this functionality and how do we allow it ?

Basically not admitted to avoid encoding issues. Ad hoc solution proposed for ivo identifiers. Text change proposed in SIA Pull request #23 . Result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

What is the price to pay to allow case-insensitive and how do we do that ?

Several string values PARAMETERS may be case insensitive, except where the "data model" forbids it (COLLECTION, FACILITY, INSTRUMENT). Text change proposed in SIA Pull request #23 . Result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

The spec clearly states that RA is in [0,360] and DEC is in [-90,90] but some POS=RANGE ... examples use -Inf and +Inf (probably copied the idea from use of open ended intervals in other params).

I consider this a bug in the example that should result in a fix and erratum because I recall we explicitly decided to not have services doing range reduction.

Done with SIA2.0 erratum 1 . Accepted 2023-04-05. (FrancoisBonnarel - 2023-05-31)

  • 1 shot discovery (and then access) to cutouts was possible in SIA1 but no more in SIA2 (github SIA issue #6)
SIAP1 had cut out and mosaic modes besides archive mode → 1 shot before access but only spatial We now have : SIAP2.0 or ObsTAP which deal with all axes

SODA : for cutouts only (all axes) +DataLink (Service descriptor and/or {links} table) → 2 shots before access (instead of 1)

Although it is pretty useful to have the 2 shots sometimes (allow the user to choose the actual limits according to ObsCore content and general context) there have been some complains (SkyView people for example also others) that the one-shot functionality disappeared. It would be perfectly possible to provide it by replacing the full retrieval or datalink url in access_url by a SODA url. SODA URL parameters are common with SIA. Where SIA Parameters values constrain the discovery, SODA parameters force the cutout dimensions.

A capability "virtual data generation" would have to be added to the service. If it exists how do we choose to provide these cutouts by a new "VIRTUAL" boolean parameter? Or by providing two lines in the response with the same obs_id ? The obscore values will be different, encluding publisher_did, but the observation will be the same

Two different ways of implementing RETRIEVEMODE PARAMETER (=VIRTUAL) can be considered. Using full SODA Queriy URL in access_url or using service descriptor with ref for all input parameters. Text change with two alternative solutions proposed in SIA Pull request #23 . Result can be seen in internal draft below. Still to be discussed. (FrancoisBonnarel - 2023-05-31)

Alberto Micol 2019/03/&4 :

SIA specifies:

"The FORMAT parameter specifies response format(s) (the access_format column from the ObsCore [7] data model). This column describes the format of the response from the access_url (see 3.1.3) so the values could be data file types (e.g. application/fits) or they could be the DataLink [8] MIME type."

The initial part of the sentence mentions "response format(s)", which that greatly overlaps,

and generates confusion (at least in my mind), with the following DALI specification:

"The RESPONSEFORMAT parameter is used so the client can specify the format of the response (e.g. the output of the job)."

The SIA FORMAT and the DALI RESPONSEFORMAT are two different things, and I think that should be better clarified

in the text of the next SIA version. Could that be done?

Done with SIA2.0 erratum 2 . Accepted 2023-04-05. (FrancoisBonnarel - 2023-05-31)

Extending VIrtual SIAP2 as described in issue re-gridding/rebinning along a specific WCS can be done by adding this functionality to the virtual data discovery functionality described in issue #6. The access URL would be a SODA URL with the additional parameters proposed in SODA issue #4

An alternative is allowing SIA1 parameters of the MOSAIC mode to SIA2 interface

This is related to a change in SODA. Text change proposed in SIA Pull request #23 . Result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

MOC (as well as STMOC, and maybe STEMOC) has proven to be a very efficient way to describe coverage of data and is used for discovery of data. It has been often discussed and also during last interop that it should be useful to query SIA services by MOC ? It should probably be with a new parameter and not via POS considering that it is probably more useful to have STMOC or STEMOC, than spatial MOC alone. This is also valid for SODA of course (SODA Issue #5). I wonder if this new parameter should not be standardized by DALI

Text change proposed in SIA Pull request #23 . Result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

There was a demand to be able to use a parameter based interface " la" SIAP2 for other dataproduct_types than cube and image DPTYPE constraint should be relaxed eg: measurements time-series etc.... CADC actually created a service like this. What could be the name? SIA is no more appropriate For time-series this has been discussed in the following ivoa note: For some dataproduct_types a specific ObsCOre extension may be needed; For TimeSeries this was discussed in recent past. see for example:


Long discussion on this led to a new specification called DAP (see below) and result can be seen in internal draft below. (FrancoisBonnarel - 2023-05-31)

* Update matching in-progress DataLink update ( GregoryDubois-Felsmann -2023-03-10)

The DataLink recommendation for how a self-description service descriptor should be written is changing, and this affects SIA because an example of such a self-description was included in the standard. (see SIA PR 22 ).

The proposed change looks needed. I suggest to repost this PR on the new DAP github repository. FrancoisBonnarel - 2023-05-31

DAP 1.0 proposal _(starting from may 2022 - FrancoisBonnarel - 2023-05-31)

Basically it was decided at the May 2022 interop to move to a new specification of a parameter based interface called 'Dataset Access Protocol" or "DAP".

The new github project starting from SIA2.0 is there :

All the changes in text from SIA2.0 to extend the scope of such a specification can be found in DAP PR #3. This PR also contains all the changes for SIA2.0 described above. The project is now idle and is there for legacy of issues and discussions. Result of all the changes can be seen in internal draft below.

FrancoisBonnarel - 2023-05-31

SODA-1.0 feedback, issues and proposals

Now available here :

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf DAP.pdf r2 r1 manage 630.9 K 2023-05-17 - 22:19 FrancoisBonnarel first attempt transition SIA -- DAP
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Topic revision: r11 - 2024-03-15 - FrancoisBonnarel
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