IVOA Data Access Layer

_Contents_

Rationale

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

** 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
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
ObjVisSAP - Object Visibility Simple Access Protocol	v1.0	2020-05-14	Working Draft	GitHub	Q2 2021
ConeSearch - Simple Cone Search	v1.1	2020-08-28	Working Draft	GitHub
EPN-TAP: Publishing Solar System Data to the Virtual Observatory *	v2.0	2020-10-27	PR & RFC	GitHub
DALI - Data Access Layer Interface	DALI-1_1-Next		Revision to 1.2	GitHub	Q4 2021
ProvSAP

• (*) ObsLocTAP. ProvTAP, EPN-TAP are managed in cooperation with the Data Model WG.

WG Sessions, Meetings & Roadmap

Upcoming events and meetings:

• DAL Running Meeting #18 - 18th April 2024 - 5:00 AM UTC (7:00 AM CET (Paris), 3:00 PM AEDT (Canberra), 10:00 PM PDT (Vancouver))
  • Topic: SODA-next + other thoughts about DAP(SIA), DataLink implementation and ProvTAP

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 Roadmap (May 2007)
• status May 2006 (.pdf)
• status May 2005 (.pdf)
• status June 2004 (.pdf)
• overview May 2004 (.pdf)

DAL future

• Feedback, prototypes, ideas and proposals

Other Current Activities

• Time Series Data (Light Curves)
• TAPImplementationNotes

Idle or Abandoned

• Parameterised Query Language (PQL)
• Footprint Access Protocol

Past Activities

• AccessData (legacy) now SODA
• DALI-1_1-Next
• Data Access Layer Interface (DALI)
• TAP Registry Extension (TAPRegExt)
• SSA-1.1 RFC
• Spectral Line Lists
• VO Query Language

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

• DAL mail archive

• Simple Image Access Protocol (SIA-1.0)
• Table Access Protocol (TAP-1.0)
• Astronomical Data Query Language (ADQL-2.0)
• Cone Search Protocol (ConeSearch-1.03)
• Simple Line Access Protocol (SLAP-1.0)
• Simple Spectral Access Protocol (SSA-1.04)

How to contribute

• subscribe to dal@ivoa.net and share your ideas
• register with the IVOA Twiki and edit this or add new pages
• contact JamesDempsey and GregoryMantelet to propose creation of a new DAL standard.