Astronomical Data Query Language

The Astronomical Data Query Language (ADQL) is the language used by the IVOA to represent astronomy queries posted to VO services. ADQL is based on the Structured Query Language, especially SQL 92; special restrictions and extensions have been defined in order to support generic and astronomy specific operations.

Current recommendation

The current IVOA Recommendation is ADQL-2.0 (30 October 2008).

ADQL-2.0-Next page collects proposed features and notes while developing the next revision of the specification. ADQL-2_0-Errata keeps track of the Errata status for this specific version of the recommendation.

ADQL-2.1-Next page collects proposed features and notes while developing the next revision of the specification.

ADQL-2.1 Proposed Recommendation

The DAL group are working on developing the next version (2.1) of the ADQL specification.

The latest version of the specification is available as HTML and PDF at PR-ADQL-2.1-20210528 (28 May 2021).

Document source

The source code for the document can be found online in the ADQL GitHub repository.

The following command can be used to checkout a local copy of the document source.

    git clone https://github.com/ivoa-std/ADQL.git

BNF grammar validation effort

At the October 2016 interop in Trieste the DAL group decided to delay putting the ADQL 2.1 working draft forward for the next stage of review because there were questions about the validity of the Backus–Naur form (BNF) definition of the language grammar included in the specification.

Prior to this, the BNF definition of the language grammar has been treated as a human readable resource that was interpreted manually by people developing ADQL parser implementations.

The October 2016 decision added a new requirement that the BNF definition of the language grammar needed to be machine readable and had to be validated against a set of standard queries.

In order to accomplish this, the Lyonetia GitHub project has been set up to develop the tools and test data needed to create a machine readable version of the grammar.

To follow and contribute to this work please refer to the project plan.

Previous versions

• DAL PR (2021-05-28): PR-ADQL-2.1-20210528 (git commit 0d5911f or git tag v2.1_20210528-pr)
• DAL Internal WD (2017-11-29): WD-ADQL-2.1-20171129 (svn revision 4594)
• DAL Internal WD (2017-10-24): WD-ADQL-2.1-20171024 (svn revision 4555)
• DAL Internal WD (2017-10-23): WD-ADQL-2.1-20171023 (svn revision 4544)
• DAL Internal WD (2016-05-02): WD-ADQL-2.1-20160502 (svn revision 3385)
• DAL Internal WD (2015-06-01): WD-ADQL-2.1-20150601 (svn revision 2983)

Associated projects

• UDF Catalogue Collections of IVOA User Defined Functions
• Cosmopterix Docker containers for common database platforms.
• Lyonetia project to validate language grammar.
• ADQL function name prefixes to avoid name conflicts.