REQUIREMENTS FOR SDSS DATA MANAGEMENT SYSTEMS

June 5, 1995

[All requirements are subject to budgetary, manpower, and technical limitations]

The data management systems shall maintain all processed data from the SDSS and provide access by SDSS scientists and operators in order to maximize the ease of the following:

  1. Operate the SDSS survey so as to maximize the efficiency of operations.
  2. Perform Quality Analysis operations on the data so as to ensure its integrity. The operations will verify calibrations, target selection criteria and classifications, and completeness & accuracy.
  3. Provide SDSS scientists with access to the data and tools to permit selection of spectroscopic targets for certain categories (serendipity; stars).
  4. Provide SDSS scientists with access to the data so as to enable scientific analyses.

Requirements for the Science Archive

The science archive shall consist of:
  1. A science database that shall:
    a. Retain calibrated object catalogs (photometric CCD output)
    b. Retain parameters from spectroscopic pipeline
    c. Enhanced goal: provide ability to recalibrate object catalogs
    d. Retain references to atlas images and extracted spectra
    e. Provide ability to carry out manual target selection for certain target categories
    f. Provide ability to carry out offline QA activities
    g. Provide ability for SDSS scientists to extract subsets of retained data.
    h. Enhanced goal: Provide ability to retain scientist-derived data sets.
    i. Enhanced goal: Provide smooth transition to public distribution system.
  2. A set of files tracked by the science database.
  3. A set of files not tracked by the science database.

I. Input to Science Archive

  1. Survey Definition
    a. A description of the North Imaging survey area
    b. Survey progress: A description of sky inserted into database to date
  2. Final Astrometric Calibration
    a. List of r' band calibration coefficients on a frame-by-frame basis.
    [TBD: Are position errors stored on an object-by-object basis?]
  3. Final Photometric Calibraton
    a. List of photometric calibration coefficients on a frame-by-frame basis.
  4. Merged Object Lists
    a. A list of calibrated objects and parameters from the Frames pipeline of photo
    b. A list of objects masks from the Frames pipeline of photo
    [TBD: Do a and b provide all information about masked areas of sky?]
    c. Run and Field information. Might be needed for recalibrations)
    d. Star/Galaxy/QSO classifications
    e. Enhanced goal: Cross-identifications to other catalogs
  5. Target Selection
    a. A list of all targetable objects with target selection categories
    b. A list of all objects from a selected as targets with selection category
    c. Tiling flags for all objects in b.
    d. Reports for all targets selected manually
  6. Spectroscopic Pipeline
    a. Redshifts and parameters of all targeted objects
    b. Enhanced goal: Tile and plate information.
    [TBD: If a target has multiple spectra obtained, is there a need to assign one as a primary measurement?]
  7. Enhanced goal: Scientist derived catalogs
  8. Enhanced goal: Other input catalogs
  9. Separate files tracked from Science Database
    a. Atlas Images
    b. 1-D spectra
  10. Separate files not tracked or accessible from Science Archive
    a. Compressed pixel map
    b. Full corrected pixel map
    c. Corrected spectroscopic frames
    d. Unused data
  11. TBD: Southern Survey

II. Functional Goals

  1. User will be able to carry out efficient queries to locate objects over one or more ranges of following attributes:
    a. Longitude or latitude in several spherical coordinates
    i) J2000 Ra and Dec
    ii) B1950 Ra and Dec
    iii) Enhanced goal: Ra and Dec of arbitrary epoch
    iv) Galactic coordinates
    v) Survey Coordinates
    vi) Any linear combination of the two coordinates
    b. Radius within a give point of the sky
    c. u' g' r' i' z' (One set of magnitudes per object)
    d. Any linear combination of c.
    e. Object radius (one per object)
    f. Surface brightess formed by c and d.
    g. Star/Galaxy/QSO Classification flag
    h. Object class (small/medium/big/mask)
    i. Target Selection Category
    j. Spectrum available flag
  2. User will be able to carry out queries on any retained object parameter (subject to implementation constraints).
  3. Enhanced Goal: All calibrated quantities can be recomputed using improved astrometric and photometric calibrations. Queries can be performed on the recalibrated quantities.
  4. For all efficient queries, return an esimated number of objects to be located.
  5. For all located objects, users shall be able to specify an arbitrary subset of stored parameters to be returned (subject to implementation constraints) plus the following derived quantities:
    a. Number of located objects
    b. TBD: Extra parameters
  6. Users shall be able to perform the following functions:
    a. Efficient repeated queries [e.g, get all objects within each of 10,000 QSOs in my favorite catalog).]
    b. Make simple plots, etc. of returned parameters (e.g., SMONGO)
    c. Formulate new queries based on results of previous queries.
    d. TBD: What else?

III. Technical Goals

  1. User interface
    a. User interface shall be developed in a TCL/Tk/TclDp environment.
    b. User interface shall communicate with a query support layer via ASCII interface protocol.
    c. Data shall be returnable to files, sockets, or pipes. Returned data shall use binary machine independent format (FITS binary, ASCII if appropriate, TBD: FITS ASCII, other?)
  2. Enhanced goal: Data shall be stored in a system providing industry-standard OSQL-like interface to enable use of commercial products to provide alternative view of the database.
    (TBD: I am not sure what this all means).
  3. Distributability
    a. A master copy of all data shall be maintained (the Master Science Archive)
    b. Capability shall be present to replicate all or part of the Master Science Archive as local databases at SDSS institutions. Replication may consist of:
    i) Science Database in its entirety
    ii) All or part of separate files tracked by Science Database
    iii) No capability shall be present to replicate an arbitrarily selected subset of the science database beyond that described by section 1.c of USER INTERFACE.
    iv) Replication of databases shall be possible on all SDSS supported platforms.
    d. No capability is required be present to replicate all or part of separate files not tracked by Science Database
  4. (TBD: Security ...)
    a. Master Science Archive shall be protected against corruption by SDSS participant users
    b. Master Science Archive shall be protected against unauthorized access by non-SDSS participants.