IVOA Data Access Layer

Rationale

The task of the Data Access Layer (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, while data providers will implement these services to publish data to the VO.

The DAL WG 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 a new DAL standard. Standards will provide guidance to data centers and survey projects when designing VO compliant interfaces. They will allow them to justify the allocation of resources for their implementation and maintenance.

Current Standards (REC)

Standard	Current	Released	Errata	Doc Source
Managed in cooperation with the Data Model WG
In cooperation with the Time Domain IG
In cooperation with the Theory IG
In cooperation with the Registry WG
Frozen
ADQL - Astronomical Data Query Language	v2.1	2023-12-15		GitHub
Datalink	v1.1	2023-12-15		GitHub
EPN-TAP: Publishing Solar System Data to the Virtual Observatory	v2.0	2022-08-22		GitHub
TAP - Table Access Protocol	v1.1	2019-09-27		GitHub
DALI - Data Access Layer Interface	v1.1	2017-05-17	Errata	GitHub
SODA - Server-side Operations for Data Access	v1.0	2017-05-17	Errata	GitHub
SimDAL - Simulation Data Access Layer	v1.0	2017-03-20		IVOA-Doc Volute SVN (old)
VTP - VOEvent Transport Protocol	v2.0	2017-03-20
SIA - Simple image Access	v2.0	2015-12-23	Errata	GitHub
TAPRegExt - A VOResource Schema Extension for Describing TAP Services	v1.0	2012-08-27	Errata	GitHub
SSA - Simple Spectral Access	v1.1	2012-02-10	Errata	GitHub
VOEvent - Sky Event Reporting Metadata	v2.0	2011-07-11		GitHub
SLAP - Simple Line Access (in collaboration with DM WG)	v1.0 REC	2010-12-09	Errata
ConeSearch - Simple Cone Search	v1.03	2008-02-22	Errata	GitHub

Ongoing Work (WD and PR)

WG Sessions, Meetings & Roadmap

Upcoming events and meetings:

• All Running Meetings
• TBD

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.

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