(r4) DALFuture < IVOA

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---+ DAL Future - discussion page

This page is meant to gather opinions, feedback and proposals for DAL future (see [[http://wiki.ivoa.net/internal/IVOA/InteropOct2016DAL/DAL_Future.pdf][Trieste 2016 Fall Interop presentation]]).

The underlying question is what will be the main evolution of the DAL protocols in a near future (SIA, !SODA, TAP, !ADQL, !DataLink, etc.).

The main drivers are:

   1 CSP priorities : what is achieved and what is not achieved.
   1 Feedback from implementation of recently recommended protocols (SIA, !DataLink, !SODA, TAP new version)
   1 Multidimensional data access roadmap as established in october 2013 in Hawaï (Fall Interop + ADASS).
Properties to consider:
   * Data Type
   * Functionalities
   * Software Design
   * Position in IVOA landscape
(see [[http://www.adass2016.inaf.it/index.php/participants-all/4-poster/163-molinaro-marco][ADASS XXVI DAL poster]] for reference)

Contribution can take the usual forms: linked pages to topics listed below (or added ones), mailing list follow up from the topics.

(please, when creating a page to link from a topic here, use a DALFutureTopic TWiki name for the new page)

---+++ Data Type

Add Time Domain ( *HIGHEST Scientific priority: see [[http://wiki.ivoa.net/twiki/bin/view/IVOA/CSPTimeSeries][CSP Time Series use cases]]*)

   * use cases
   * ideas for solutions
   * attempts and prototypes reports

---+++ Functionalities

   * Feedback : what is missing/inadequate in current protocols
   * Extended metadata (for Cubes and Time Domain)
   * Extended server side data services (regridding, deconvolution, etc.)

---+++ Software Design

---+++++ Interface design

   * Feedback on current interfaces

Recently I discovered that  calls to datalink+SODA, outside ObsCore and SIAv2 context are available in VizieR, but also in GAVO. Markus is now using in SIA 1.0 responses (see  http://dc.zah.uni-heidelberg.de/lswscans/res/positions/siap/siap.xml?POS=311.41098458333335,30.723715361111108&SIZE=2.64&FORMAT=image/fits) It sounds reasonable and  I can imagine we wil find more of that in the future. But here there are already fields with  utypes Access.Reference in le SIA mai n part, it is now  difficult/impossible to recognize that a given link will return Datalink or something else.

On the other side, the  Datalink VOTable response doesn't  contain any signature allowing to  recognize a posteriori that it has a  datalink content. That's a pity This would have been harmless and could simplify everything/ 

This has direct consequence on  Aladin v10 (or any other cleint), which has the code necessary to perform specific actions for DataLink. , passe à coté de tous ces efforts de standardisation, et se contente d'afficher les résultats, au mieux sous forme d'une VOTable basique (sans coordonnées - donc en fait quasi-inutilisable dans Aladin), ou pire, dans un navigateur Web. 

Le coté positif, c'est qu'on est proche d'une réelle utilisation et plus uniquement du prototypage, et probablement plus large que ce que vous aviez imaginé à l'origine de datalink (c'est plutôt une bonne chose). Aladin n'est pas loin d'arriver à en faire quelque chose et il y a désormais qq serveurs qui en fournissent. Juste que chacun l'utilise un peu à sa façon et c'est au final galère pour le client de simplement repérer ces liens particuliers. Triste ! Alors qu'il suffirait de presque rien en plus pour s'en sortir.

Donc, j'attire l'attention sur ces deux améliorations qui seraient les bienvenues :

    Un moyen simple de repérer les liens et surtout de savoir ce qu'il vont retourner
        solution 1: un utype spécifique pour les URL datalink (ex: utype=Access.Reference.Datalink.1.xxx")
        solution 2: un <LINK adéquat dans le FIELD de la colonne (ex: <FIELD content-type="application-stream/votable;datalink" ...>)
    Une signature dans le VOTable, par exemple dans une balise <INFO> ou dans un attribut de la ressource <RESOURCE type="result;datalink"...>

Les solutions que je propose ne sont données qu'à titre d'exemples, il faudrait vérifier que ça colle bien avec les standards existants.

   * Driving extended functionalities
   * Standard definition of custom services

---+++++ Pushing code to the data

   * Science cases
   * Attempts and prototypes

---+++++ Formats and Languages

   * Json, !PQL, PDL, etc.
   * What to use next ?

---+++ TAP evolution

   * From relational databases to...
   * Relaxing !ADQL ?

---+++ Position in IVOA landscape

---+++++ Merging DAL protocols, !HiPS and MOC

   * !HiPS is also a discovery and access mode: How to marry service approach and !HiPS Approach in both ways ?
   * Querying services by MOC : is that necessary ?

---+++++ Data Models

   * !ObsCore
   * !DataSet Metadata
   * ND-Cube
   * !SparseCube
   * !STC
   * other...

---+++++ Updating SCS

SCS still requires VOTable 1.1 and has some other quirks that makes it needlessly incompatible with the rest of the DAL landscape (in particular, it's totally DALI-incompatible). We should figure out how we can evolve it to be less odd with minimal disruption to existing services and clients (e.g., relaxing VOTable requirements, support for DALI MAXREC, RESPONSEFORMAT, metadata discovery).  -- IVOA.MarkusDemleitner - 2017-03-01
Topic revision: r4 - 2017-03-07 - FrancoisBonnarel
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