IVOA Data Access Layer



The task of the DAL working group is to define and formulate VO standards for remote data access. Client data analysis software will use these services to access data via the VO framework; data providers will implement these services to publish data to the VO. The DAL working group will define the scope of the DAL standards, outline a process by which DAL standards are defined, and generate the initial version 1.0 of the DAL standard. This standard will provide guidance to data centers and survey projects when designing VO compliant interfaces. It will allow them to justify the allocation of resources for its implementation and maintenance. Once the work on Version 1.0 is accomplished the working group will coordinate future development of the standard.

Current Standards

Standard Current Released Errata Next Doc Source
ADQL - Astronomical Data Query Language v2.0 REC 2008-10-30 Errata   GitHub
DALI - Data Access Layer Interface v1.1 REC 2017-05-17 - 1.1 Next GitHub
Datalink v1.0 REC 2015-06-17 Errata 1.0 Next GitHub
ObsLocTAP - Observation Locator Table Access Protocol * v1.0 2021-07-24 -   GitHub
SimDAL - Simulation Data Access Layer ** v1.0 REC 2017-03-20 -   Volute SVN
ConeSearch - Simple Cone Search v1.03 REC 2008-02-22 Errata 1.03 Next GitHub
SIA - Simple image Access v2.0 REC 2015-12-23 - 2.0 Next GitHub
SLAP - Simple Line Access v1.0 REC 2010-12-09 -   ??
SODA - Server-side Operations for Data Access v1.0 REC 2017-05-17 Errata 1.0 Next GitHub
SSA - Simple Spectral Access v1.1 REC 2012-02-10 Errata   ?? GitHub for issues
TAP - Table Access Protocol v1.1 REC 2019-09-27 Errata 1.1 Next GitHub
TAPRegExt - A VOResource Schema Extension for Describing TAP Services ** v1.0 REC 2012-08-27 -   GitHub
VOEvent Transport Protocol * v2.0 REC 2017-03-20 -   GitHub

* ObsLocTAP, ProvTAP are managed in cooperation with the Data Model WG

** Registry standard developed by the DAL working group.

* Interest group developed standard endorsed and administered by the DAL working group.

Ongoing Work

Standard Version Date Status Doc Source Expected Release
ADQL - Astronomical Data Query Language v2.1 2021-05-28 Proposed Recommendation GitHub Q1 2022
ConeSearch - Simple Cone Search v1.1 2020-08-28 Working Draft GitHub  
DALI - Data Access Layer Interface DALI-1_1-Next   Revision to 1.2 GitHub Q4 2021
Datalink DataLink-1_0-Next   Revision to 1.1 GitHub  
EPN-TAP: Publishing Solar System Data to the Virtual Observatory * v2.0 2020-10-27 PR & RFC GitHub  
ObjVisSAP - Object Visibility Simple Access Protocol v1.0 2020-05-14 Working Draft GitHub Q2 2021
ProvTAP - Provenance Table Access Protocol * v0.1 2019-03-22 (internal) WD    
SLAP - Simple Line Access Protocol v2.0 2019-04-09 Working Draft Volute SVN pending SSLDM-2.0

WG Sessions, Meetings & Roadmap

Upcoming events and meetings:

  Interop DAL sessions DAL Running Meetings DAL Roadmaps
2021 November 2021 Virtual Interop 2021-09-08 RM#12  
2021-06-30 RM#11
May 2021 Interop (online) 2021-04-28 RM#10 2021A DAL Roadmap
2021-03-24 RM#9
2021-02-24 RM#8
2021-01-27 RM#7
2020 2020-12-09 RM#6
November 2020 Virtual Interop 2020-11-04 RM#5 2020B DAL Roadmap
2020-09-30 RM#4
2020-09-02 RM#3
2020-07-27 RM#2
May 2020 Virtual Interop 2020-06-29 RM#1 2020A DAL Roadmap

Previous sessions and meetings can be found starting from the IVOA Events wiki page.

Previous DAL Roadmaps can be found starting from the IVOA TCG wiki page in the IVOA Technical Assessment and Roadmap Documents section.

Older roadmaps can be found here:

DAL future

Other Current Activities

Idle or Abandoned

Past Activities

Notes on Defining a DAL Standard

This page contains some ideas and definitions to help frame the definition of DAL standards. To be discussed.

Notes on Defining new service parameters

This page contains some hints to help defining new service paremeters according to the 3 factor semantics.

Recommended reading

How to contribute

Topic attachments
I Attachment Action Size Date Who Comment
PDFpdf DAL-Cambridge-Report.pdf manage 145.8 K 2003-10-23 - 21:01 DougTody Cambridge DAL WG Plenary Report
PowerPointppt DAL-Strasbourg-Report.ppt manage 987.5 K 2003-10-23 - 20:35 DougTody Strasbourg DAL WG Plenary Report
Microsoft Word filedoc IVOA-DAL-Jul03.doc manage 38.0 K 2003-07-23 - 06:10 MarkusDolensky DAL Progress Report July 03 by D. Tody
PDFpdf IVOA-DAL-Jul03.pdf manage 19.3 K 2003-07-23 - 06:09 MarkusDolensky DAL Progress Report July 03 by D. Tody
PDFpdf TAP-Analysis.pdf manage 419.7 K 2007-09-26 - 16:06 KeithNoddle  
PDFpdf TAP-draft.pdf manage 79.8 K 2007-09-26 - 16:06 KeithNoddle  
PDFpdf dalsedspec.pdf manage 1218.9 K 2003-10-18 - 16:16 MarkusDolensky SEDs & AVO prototype and ... (.pdf)
PowerPointppt dalsedspec.ppt manage 284.5 K 2003-10-18 - 15:38 MarkusDolensky SEDs & AVO prototype and evolution to SSA
PDFpdf ranking-v01.pdf manage 100.9 K 2006-05-12 - 14:35 MarkusDolensky Ranking Query Result Sets
PowerPointppt sIAevol1.ppt manage 37.5 K 2003-10-23 - 20:48 DougTody URL templating etc. proposals by F. Bonnarel
PDFpdf spie04-5493-47.pdf manage 527.6 K 2004-07-01 - 15:16 MarkusDolensky SSA poster, status June 2004, 3x3 ft.
Microsoft Word filedoc ssa-v01-MD.doc manage 4752.0 K 2004-09-25 - 14:12 MarkusDolensky SSA Spec. V0.1
XMLxml ssample1.xml manage 31.3 K 2004-09-25 - 13:31 MarkusDolensky SSA sample SED serialization in VOTable format
XMLxml ssample20041021.xml manage 31.8 K 2004-10-21 - 13:46 MarkusDolensky VOTable serialization; SSA data format
Topic revision: r132 - 2021-11-02 - JamesDempsey
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