VODA - A Sampo Project

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VODA - A Sampo Project

• Johan Lindroos CSC Scientific Computing Ltd,
  Finland
• Pekka Järveläinen CSC Scientific Computing
  Ltd, Finland
• Richard Hook - ESO, Garching, Germany
• http//www.eso.org/sampo lindroos_at_csc.fi

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Introduction and Motivation

• Sampo is a collaborative project between Finland
  and ESO to investigate future data processing
  requirements and technologies and perform pilot
  studies
• A small part of Sampo has been looking at the VO,
  and specifically the relationship between remote
  VO resources and local data analysis applications
• VODA is an experiment to establish a personal,
  persistent local virtual directory of VO data
  resources and link this with visualization tools
  and the VO itself using the Astro Runtime (AR)
  and Plastic

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High-Level Architecture
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Virtual Directory?

• A local, persistent, private view of the VO
• Storing references to remote and local data and
  metadata
• User may organize these references
• Visualize (Aladin/TOPCAT/DS9 etc.)
• User may add new resources to his library from
  new queries or from external sources
• An application interface is on the way

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Data discovery - in a general way...

• VODA uses the Astrogrid Astro Runtime (AR) for
  access to VO resources through standard IVOA
  protocols (Registry, SIAP, SSAP, Cone etc.)
• Results can be stored in the Virtual Directory,
  visualized directly by local tools, downloaded,
  or passed to Plastic-aware applications
• The Virtual Directory can be updated with search
  results from any search tool that is Plastic-aware

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Downloading data

• References in the Virtual Directory can be
  downloaded to a local disk when required
• In future, a download directly into VOSpace could
  be possible
• Download isnt needed for browsing metadata
• Handles download for tools which demand local
  data (eg, DS9)

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Why the Astrogrid AR?

• The Astrogrid Astro Runtime (AR) allows simple
  access to the Astrogrid Registry and to
  application and data-services (SIAP, Cone Search
  etc)
• AR also offers the possibility of future access
  to MySpace/VOSpace
• Use of AR hides future changes of IVOA standards
  from VODA itself
• Using the AR is much easier than re-implementing
  all its facilities from scratch!

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Experiences with VO-standards

• IVOA standards allow the construction of a very
  general tool which makes few assumptions about
  the data products - as intended!
• Some problems were encountered when services do
  not support the specifications fully (eg, some
  SIAP services do not supply all the expected
  metadata)     
• We had some problems with the very large number
  of optional parameters (eg, coverage) in the
  registry and were unable to rely on these when
  querying the registry

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Why Plastic? Experiences...

• Plastic is EASY and QUICK - only a few days were
  needed for a basic implementation of a connection
  with and between Plastic-enabled tools and VODA
• Any new tools implementing certain messages in
  Plastic will automatically function with VODA
• Plastic allows VODA to pass data references to
  visualization tools and also ingest VOTables from
  Plastic-enabled tools such as TOPCAT
• You get a lot for free!
• Next step is using Plastic-aware versions of
  tools like AstroScope/DataScope for the discovery
  phase

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Conclusions

• VODA is a simple experimental implementation of
  the Virtual Directory concept
• The use of Astro Runtime greatly eases access to
  multiple VO services
• The use of Plastic allows very flexible and
  convenient two-way communication with other
  (powerful and mature) VO tools
• The use of these elements, talking standard
  protocols, means that new VO tools may be quickly
  and easily developed in a modular way