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Data Really Stored into the SaadaDB

A brief explanation about the Saada data storage

>> Accepted Product Formats

- Saada supports both FITS table and VOTables data files

- Saada can also store flat files (any format). File content is not read in this case. Saada behaves as a file repository.

 Product Categories. Saada supports 5 different categories of data. Each one is processed with a specific way. The category names given below are those used by SaadaQL

- MISC : (miscellaneous). Basic product without extension to load. Can be either a FITS file or a VOTable

- IMAGE : Must be a FITS file. The data loader handles image extensions and mansges WCS keywords.

- SPECTRUM : Fits file or VOTable. The data loader handles spectral coordinates (channel but not flux)

- TABLE : Fits file or VOTable. The data loader stores table header and table rows,

- FLATFILE : Can be any file format. The data loader just manages a download facility.

 What is Loaded in your SaadaDB. This chapter doesn’t concern FLATFILES products where data content is ignored.

- On Column per Keyword. The SaadaDB contains on column per keyword read.

  • Column Description. Keywords are renamed to be compliant with Java and SQL (lowercase, bad characters replaced with ’_’ and ’_’ as first character). The available column meta-data are stored by SaadaDB (Native name, Saada name, unit, ucd, comment, utype and VO datmodel).
  • Column Units are stored but values are not converted at loading time. The operator must take care with units when he loads heterogeneous datasets.

- Keywords Read. Basically all keywords of the file header and (almost, see below) all keywords of the selected extension (see how to do) are stored. The datalaoder can be configured to ignore some keywords (see how to do).

  • File Header Keyword
    • FITS Files. All keywords of the primary HDU are read.
    • VOTable. Saada1.5 loads the first resource of the VOTable. One column is built with each PARAMS XML field in addition with the resource name, the resource description, the table name and the coordinate system.
  • SPECTRUM Extension.
    • FITS files : All keywords of the extension containing the spectral data are loaded.
    • VOTable : No extra data are loaded in addition with the table description. Spectrum data are just explored to set the spectral range.
  • IMAGE Extension :
    • FITS files : All keywords of the extension containing the image data are loaded.
    • VOTable : Not supported for images.
  • TABLE extension : Table are splited in two Saada classes (or SQL tables) : One for the table header and one for the table entries.
    • FITS files : All keywords of the extension containing the table data are loaded except those beginning with TFORM, TUNIT, TDISP and TRUEN. Just the FITS column names are stored actually. The entry table has on column for each FITS column.
    • VOTable : No extra data are loaded in the table header. The entry table has one column for each declared XML FIELD.
last update 2016-06-07