Changes between Initial Version and Version 1 of DataModel18


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Timestamp:
06/09/05 11:58:05 (14 years ago)
Author:
joe
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  • DataModel18

    v1 v1  
     1= VSO Data Model = 
     2== Version 1.8 == 
     3 
     4 
     5 
     6== Introduction == 
     7The VSO Data Model provides a set of template descriptions for information 
     8required to describe, access, and search solar data sets in a variety of 
     9archives.  It is an abstract model, not a suggested set of keywords to be 
     10used in data nor in databases.  Because of the ubiquity of the FITS standard 
     11and the wide use of certain conventions, we provide illustrative values of 
     12FITS keywords for certain data elements; but neither the adoption of any 
     13set of particular keywords nor the FITS data model at all are required 
     14for a data description to conform to the model.  The VSO Element Names, 
     15are used at a level of abstraction once removed from the search parameters 
     16of the data providers.  They should be completely internal to the VSO 
     17procedures for decoding information from user interfaces, not sent in 
     18in queries to data providers.  We have deliberately avoided the use of 
     19FITS-compatible keyword names to emphasize this point. 
     20 
     21== VSO Search Parameters == 
     22 
     23VSO search parameters are those data descriptors for which queries 
     24are supported by the VSO in behalf of client applications or requests. 
     25These are the parameters that can best discriminate among a large 
     26collection of heterogeneous data.  They must therefore be supported 
     27by the data providers as search parameters applicable to a large 
     28subset of the data archives.  They must map to parameters in the 
     29server data dictionaries in a well-defined and meaningful way. 
     30They must also be selected so that the number of data sets meeting 
     31a particular selection criterion is small compared to the total number: 
     32for the VSO an astronomical type search parameter of Object (Sun) is 
     33not particularly useful as a discriminator. 
     34 
     35 
     36The VSO search parameters are divided into a few groups, each 
     37described under one of the major subsections.  These categories are 
     38understood to be orthogonal, in the sense that they can be used to 
     39construct non-trivial ''AND'' queries.  Of course they are not 
     40strictly orthogonal: selection of a particular data source (instrument) 
     41may automatically restrict the available observing times for example, 
     42and vice-versa.  Nonetheless it is useful to treat the major categories 
     43as if they were orthogonal and treat any dependencies as implicit 
     44selections or limits. 
     45 
     46 
     47No particular set of search parameters is required. In the absence 
     48of a relevant element or group of elements in its data description, a 
     49dataset is assumed to match all queries.  For example, if no wavelength 
     50information is supplied, then the server will return all records for any 
     51selected (or deselected) wavelength interval.  If a parameter is not 
     52searchable but has a default value, then that value can be supplied directly 
     53in the data description.  For example, an archive of data all taken at the 
     54same wavelength is unlikely to have wavelength as a searchable key in 
     55its database, but could (and should) supply that wavelength as a fixed 
     56value in its data description to avoid inappropriate satisfaction of 
     57client queries. 
     58 
     59 
     60The current parameter list is not intended to be exhaustive, and it may 
     61be useful to add additional search elements and categories in future. 
     62The categories chosen are those for which the VSO either has attempted 
     63to implement a search service or contemplates doing so.  So far, only a 
     64few of the parameters can be searched in the VSO, and these are marked 
     65with asterisks in the following list.  The elements are described in 
     66detail by group under the following sections. 
     67 
     68 
     69 * '''[wiki:ObservingTime Observing Time]''' 
     70   * '''Observation_Time'''* 
     71   * '''Duration''' 
     72   * '''Time_Step''' 
     73 
     74 * '''[wiki:TargetLocation Target Location]''' 
     75   * '''Observation_Center_West''' 
     76   * '''Observation_Center_North''' 
     77   * '''Bounding_Radius''' 
     78 * '''[wiki:ObserverLocation Observer Location]''' 
     79 * '''[wiki:SpectralRange Spectral Range]''' 
     80   * '''Wave_Type''' 
     81   * '''Wave_Bands''' ''(may be deleted in future versions)'' 
     82   * '''Wave_Minimum'''* 
     83   * '''Wave_Maximum'''* 
     84   * '''Wave_Step''' ''(may be deleted in future versions)'' 
     85 * '''[wiki:PhysicalObservable Physical_Observable]'''* 
     86 * '''[wiki:DataOrganization Data Organization]''' 
     87 * '''[wiki:WaveModeSampling Wave Mode Sampling]''' 
     88   * '''Degree_Minimum''' 
     89   * '''Degree_Maximum''' 
     90   * '''Degree_Step''' ''(may be deleted in future versions)'' 
     91 * '''[wiki:DataSource Data Source]''' 
     92   * '''Observatory'''* 
     93   * '''Instrument'''* 
     94   * '''Provider'''*