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IVOA Data Access Layer

Contents

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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.

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Sub-Topics

• Table and Catalog Data (TAP)
• Spectral Data (SSA)
• Image Access (SIA)
• Spectral Line Lists
• Cone Search
• ...

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WG Roadmap

• Current DAL Roadmap (May 2007)
  Updated as of the close of the Beijing sessions, May 2007

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

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Forthcoming meetings

Cambridge Interop, September 2007

As input to the TAP discussions in the DAL-2 sessions, we have two Notes to help us progress the standards. I would urge everyone to try to read these before the meeting. I have also put together some process notes which I believe will help us move the standards effort forwards by providing a mechanism for us to push on with the areas where consensus has been reached whilst ensuring other areas still under discussion are not lost. Again, I would urge folk to read it before the meeting.

• TAP Note 1
• TAP Note 2
• Process notes

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Notes on Defining a DAL Standard

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

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Achievements so far

WG agreements have been reached in a number of areas:

• Concept of DAL portal
• DAL scope and high level architecture
• Principal data types within the scope of the DAL
• Mapping of data types to access services
• Priorities for implementing the data access services
• Roadmap and priorities for the next year
• Enhancements to SIA V1.1

See also the DAL report from July 03 (.pdf) and the plenary summary presentation (.pdf) from the Cambridge (May 2003) meeting.

Current Activities

• Results of Survey among Spectral Data Providers and Consumers
• ADASS XIII Tutorial Oct. 12, 2003
• WG meeting minutes and summary presentation, Strasbourg 16-17 Oct. 2003
• gather requirements, property lists, interface issues, priorities, schedules as we go along
• WG meeting, Cambridge (Mass., USA) 25/26 May 2004
• Spectral Data Model

Recommended reading

• Simple Image Access Protocol Specification
• Incorporating Spectra in the Next Phase of the Virtual Observatory
• SIAP Extension RFC and Draft Specification, Part1: Quantities and Coordinates, V1.0 (.pdf)
• SSA Poster, status June 2004 (.pdf)
• DAL mail archive; see also NVO mail archive

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 KeithNoddle or MarkusDolensky to propose creation of a new DAL standard.

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