SIA, Data Access Layer for Astronomical images

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SIA, Data Access Layer for Astronomical images

• F.Bonnarel
• (CDS/Observatoire de Strasbourg)
• bonnarel_at_astro.u-strasbg.fr

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Data Access Layer

• Software layer used to request datasets and
  databases. (For us on the VO )
• Class/methods (WEB services) or HTTP/GET
• Different specific protocols for different kinds
  of data
• ConeSearch (obsoleted)
• SIA
• SSA
• Etc

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Images

• Availability problem distinction between
  "ImageQuery" and "ImageRetrieval"
• ( What is available at this position / give
  me the image)
• Query parameters and descriptions standardisation
• Full image Characterization, detailed and
  structured metadata, links between images

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Availability problem
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The SIA 1.0 IVOA Working draft

• Origin
• NVO (Doug Tody et al) mid-2002 first draft
• First implementations in NVO and AVO demos
  January and June 2003
• Cgi service with query parameters defined by the
  protocol
• VOTable output one single RESOURCE and TABLE,
  FIELDS
• Possible encapsulation as a WebService

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The SIA 1.0 DataModel

• Image Pixel Array
• Image header describing the image
  (Selected metadata)
• The geometry
• Scale
• Format
• Position
• (WCS)
• (Spectral bandpass)

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SIA 1.0 the protocol -1 (misc
query method input parameters)

• 4 kind of services atlas, pointed, cutout,
  mosaic.
• 3 methods image query, image retrieval,image
  staging.
• Query parameters 3 Required
• POS (center of "Region of Interest - ROI")
• SIZE (ROI size)
• FORMAT (3 values METADATA, IMAGE, TEXT)
• INTERSECT Query Parameter 4 search mode in the
  ROI
• OVERLAPS (non-empty intersection ROI,image)
• CENTER (image center in ROI)
• ENCLOSED (image included in ROI)
• COVER (ROI included in image)

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Sia 1.0 protocol -2 (query
method input parameters)

• Query parameters Image Generation Parameters
  size and WCS ("old-style") definition for
  output image meanless outside cutout service or
  mosaic service
• CFRAME, EQUINOX, CRPIX, CRVAL, CDELT,
  ROTANG, PROJ
• Query parameters FORMAT with values
  image/fits,image/png, GRAPHIC.
• Query parameter VERB
• Query parameter Service defined (BAND, SURVEY,
  etc)

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Sia 1.0 protocol -3 (query
method response)

• VOtableone RESOURCE of type results, INFO
  element
• unique TABLE Fields
• (ill) defined by their "ucd" (actually
  pseudo-UCD, not used as ucds)
• _ Required
• POS_EQ_RA and POS_EQ_DEC (centre position)
• VOXImage_Naxes et VOXImage_Naxis (axes number
  and length)
• VOXImage_Scale et VOXImage_Format (pixel size
  and fits/jpeg/)
• VOXImage_AccessReference

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Sia 1.0 protocol -4 (query
method response)

• Recommended or optional first order WCS
• VOXSTC_CoordRefFrame
• VOXSTC_CoordRefPixel
• Etc
• Bandpass with details,
• VOXBandPass_ID
• VOXBandPass_RefValue
• Etc
• Processing Metadata VOXImage_PixFlags
• Access metadata VOXImage_FileSize .

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Accessible services for this position
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SIA 1.0 Image staging and Retrieval

• Image staging only preliminary recommendations.
• should be a SOAP based Web Service
• The request message contains list of
  references extracted from the image query phase
• Image retrieval
• a getImage method with one single input
  parameter the URL of the Image.

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Service Registration
Go to http//nvo.stsci.edu/VORegistry/Publish.aspx
Edit an old SIA service and modify it
See K.Benson lecture
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SIA towards SIA 1.1 (October 2005)-1

• New query parameters and upgraded request
  Response
• similar to SSA0.9 (See P.Osuna talk for
  details on that)
• Use Ucd1 for Fields
• Distinguish Ucd1 from utypes.
  (observation center position
  pos.eq.ra
• versus
• characterization/spatial/coverage/location/co
  ordinate/Value21 )
• IVOA utypes will be based on Characterization
  DataModel

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Characterization Model UML diagram
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SIA towards SIA 1.1 (October 2005) -2

• Logical names (to group similar images)
• Extensions
  IVOA note
  Osuna/Salgado CDS (add new resources and xml
  elements, for additional metadata indexing
  mechanisms)
• implementation CGPS
• Field templating (eg URL) ?

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CGPS Metadatatree in Aladin From SIA with
extensions
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CGPS HI cube slice/access From SIA with extensions
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URLs to consult (webography)Tutorial

• SIA 1.0
• http//www.ivoa.net/Documents/WD/SIA/sia-2004
  0524.html
• Ucd and SIA http//www.ivoa.net/forum/ucd/0306/00
  48.htm
• http//www.ivoa.net/f
  orum/dal/0403/0119.htm
• SIA extension, http//www.ivoa.net/Documents/DalR
  esp.html/
• see also dal forum, http//www.ivoa.net/forum/dal/
  
• SSA0.9 http//www.ivoa.net/internal/IVOA/InterOpM
  ay2005DAL/ssa-v090.pdf
• Characterization
• http//alinda.u-strasbg.fr/Model/Characteris
  ation/
• DAL TUTORIAL by the ESAC GROUP SIAP, SSAP ,
  basic, advanced