Changes between Version 2 and Version 3 of DataModel18


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Timestamp:
11/11/21 22:21:21 (7 months ago)
Author:
alisdair
Comment:

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  • DataModel18

    v2 v3  
    1 = VSO Data Model = 
    2 == Version 1.8 == 
     1= VSO Data Model - Version 1.8 = 
    32 
    43== Introduction == 
    5 The VSO Data Model provides a set of template descriptions for information 
    6 required to describe, access, and search solar data sets in a variety of 
    7 archives.  It is an abstract model, not a suggested set of keywords to be 
    8 used in data nor in databases.  Because of the ubiquity of the FITS standard 
    9 and the wide use of certain conventions, we provide illustrative values of 
    10 FITS keywords for certain data elements; but neither the adoption of any 
    11 set of particular keywords nor the FITS data model at all are required 
    12 for a data description to conform to the model.  The VSO Element Names, 
    13 are used at a level of abstraction once removed from the search parameters 
    14 of the data providers.  They should be completely internal to the VSO 
    15 procedures for decoding information from user interfaces, not sent in 
    16 in queries to data providers.  We have deliberately avoided the use of 
    17 FITS-compatible keyword names to emphasize this point. 
     4The VSO Data Model provides a set of template descriptions for information required to describe, access, and search solar data sets in a variety of archives. It is an abstract model, not a suggested set of keywords to be used in data nor in databases. Because of the ubiquity of the FITS standard and the wide use of certain conventions, we provide illustrative values of FITS keywords for certain data elements; but neither the adoption of any set of particular keywords nor the FITS data model at all are required for a data description to conform to the model. The VSO Element Names, are used at a level of abstraction once removed from the search parameters of the data providers. They should be completely internal to the VSO procedures for decoding information from user interfaces, not sent in in queries to data providers. We have deliberately avoided the use of FITS-compatible keyword names to emphasize this point. 
    185 
    196== VSO Search Parameters == 
    20  
    21 VSO search parameters are those data descriptors for which queries 
    22 are supported by the VSO in behalf of client applications or requests. 
    23 These are the parameters that can best discriminate among a large 
    24 collection of heterogeneous data.  They must therefore be supported 
    25 by the data providers as search parameters applicable to a large 
    26 subset of the data archives.  They must map to parameters in the 
    27 server data dictionaries in a well-defined and meaningful way. 
    28 They must also be selected so that the number of data sets meeting 
    29 a particular selection criterion is small compared to the total number: 
    30 for the VSO an astronomical type search parameter of Object (Sun) is 
    31 not particularly useful as a discriminator. 
    32  
    33  
    34 The VSO search parameters are divided into a few groups, each 
    35 described under one of the major subsections.  These categories are 
    36 understood to be orthogonal, in the sense that they can be used to 
    37 construct non-trivial ''AND'' queries.  Of course they are not 
    38 strictly orthogonal: selection of a particular data source (instrument) 
    39 may automatically restrict the available observing times for example, 
    40 and vice-versa.  Nonetheless it is useful to treat the major categories 
    41 as if they were orthogonal and treat any dependencies as implicit 
    42 selections or limits. 
    43  
    44  
    45 No particular set of search parameters is required. In the absence 
    46 of a relevant element or group of elements in its data description, a 
    47 dataset is assumed to match all queries.  For example, if no wavelength 
    48 information is supplied, then the server will return all records for any 
    49 selected (or deselected) wavelength interval.  If a parameter is not 
    50 searchable but has a default value, then that value can be supplied directly 
    51 in the data description.  For example, an archive of data all taken at the 
    52 same wavelength is unlikely to have wavelength as a searchable key in 
    53 its database, but could (and should) supply that wavelength as a fixed 
    54 value in its data description to avoid inappropriate satisfaction of 
    55 client queries. 
    56  
    57  
    58 The current parameter list is not intended to be exhaustive, and it may 
    59 be useful to add additional search elements and categories in future. 
    60 The categories chosen are those for which the VSO either has attempted 
    61 to implement a search service or contemplates doing so.  So far, only a 
    62 few of the parameters can be searched in the VSO, and these are marked 
    63 with asterisks in the following list.  The elements are described in 
    64 detail by group under the following sections. 
    65  
    66  
    67  * '''[wiki:ObservingTime Observing Time]''' 
    68    * '''Observation_Time'''* 
    69    * '''Duration''' 
    70    * '''Time_Step''' 
    71  
    72  * '''[wiki:TargetLocation Target Location]''' 
    73    * '''Observation_Center_West''' 
    74    * '''Observation_Center_North''' 
    75    * '''Bounding_Radius''' 
    76  * '''[wiki:ObserverLocation Observer Location]''' 
    77  * '''[wiki:SpectralRange Spectral Range]''' 
    78    * '''Wave_Type''' 
    79    * '''Wave_Bands''' ''(may be deleted in future versions)'' 
    80    * '''Wave_Minimum'''* 
    81    * '''Wave_Maximum'''* 
    82    * '''Wave_Step''' ''(may be deleted in future versions)'' 
    83  * '''[wiki:PhysicalObservable Physical_Observable]'''* 
    84  * '''[wiki:DataOrganization Data Organization]''' 
    85  * '''[wiki:WaveModeSampling Wave Mode Sampling]''' 
    86    * '''Degree_Minimum''' 
    87    * '''Degree_Maximum''' 
    88    * '''Degree_Step''' ''(may be deleted in future versions)'' 
    89  * '''[wiki:DataSource Data Source]''' 
    90    * '''Observatory'''* 
    91    * '''Instrument'''* 
    92    * '''Provider'''* 
    93  
    94  
    95  
    96 == Suggestions for Additional Search Parameters == 
    97  
    98 The following search parameters or categories are under consideration 
    99 for possible inclusion in future versions of the VSO Data Model: 
    100  
    101  
    102   * Data processing information - menu? 
    103   * Data format - menu? 
    104     Possible data formats may include: 
    105     ''ASCII, FITS, JPEG, GIF, PNG, MPEG, TIFF'' 
    106  
    107  
    108 == Nicknames == 
    109  
    110 Nicknames for famous combinations of Search Parameters were introduced 
    111 in Version 1.7 of the Data Model in a separate table.  Here they are 
    112 incorporated in the defining document.  Certain problems remain to be 
    113 resolved.  For example, mechanisms are required for designating a logical 
    114 OR of menu-type parameters, and for specifying whether a Bounding_Radius 
    115 is an inner radius or an outer radius. 
    116  
    117 [wiki:CurrentNicknames Current Nicknames] 
    118  
    119  
    120  
     7VSO search parameters are those data descriptors for which queries are supported by the VSO in behalf of client applications or requests. These are the parameters that can best discriminate among a large collection of heterogeneous data. They must therefore be supported by the data providers as search parameters applicable to a large subset of the data archives. They must map to parameters in the server data dictionaries in a well-defined and meaningful way. They must also be selected so that the number of data sets meeting a particular selection criterion is small compared to the total number: for the VSO an astronomical type search parameter of Object (Sun) is not particularly useful as a discriminator.  
     8The VSO search parameters are divided into a few groups, each described under one of the major subsections. These categories are understood to be orthogonal, in the sense that they can be used to construct non-trivial AND queries. Of course they are not strictly orthogonal: selection of a particular data source (instrument) may automatically restrict the available observing times for example, and vice-versa. Nonetheless it is useful to treat the major categories as if they were orthogonal and treat any dependencies as implicit selections or limits.  
     9No particular set of search parameters is required. In the absence of a relevant element or group of elements in its data description, a dataset is assumed to match all queries. For example, if no wavelength information is supplied, then the server will return all records for any selected (or deselected) wavelength interval. If a parameter is not searchable but has a default value, then that value can be supplied directly in the data description. For example, an archive of data all taken at the same wavelength is unlikely to have wavelength as a searchable key in its database, but could (and should) supply that wavelength as a fixed value in its data description to avoid inappropriate satisfaction of client queries.  
     10The current parameter list is not intended to be exhaustive, and it may be useful to add additional search elements and categories in future. The categories chosen are those for which the VSO either has attempted to implement a search service or contemplates doing so. So far, only a few of the parameters can be searched in the VSO, and these are marked with asterisks in the following list. The elements are described in detail by group under the following sections.  
     11         
     12* Observing Time  
     13  * Observation_Time*  
     14  * Duration  
     15  * Time_Step  
     16* Target Location  
     17  * Observation_Center_West  
     18  * Observation_Center_North  
     19  * Bounding_Radius  
     20* Observer Location  
     21* Spectral Range  
     22  * Wave_Type  
     23  * Wave_Bands (may be deleted in future versions)  
     24  * Wave_Minimum*  
     25  * Wave_Maximum*  
     26  * Wave_Step delete?  
     27* Physical_Observable*  
     28* Data Organization  
     29* Wave Mode Sampling  
     30  * Degree_Minimum  
     31  * Degree_Maximum  
     32  * Degree_Step delete?  
     33* Data Source  
     34  * Observatory*  
     35  * Instrument*  
     36  * Provider* 
     37  
     38== 1. Observing Time == 
     39Observing time is by general consensus the most likely parameter to be used as a first case for searches, the most ubiquitous indexing parameter for data, and one on which there is widespread agreement and understanding of representations, scales, and units. Most of the complexity involved is in the descriptions of data translation. Here it is sufficient to specify a simple uniform description. \\ 
     40(Most observational data are expected to be associated with observing times, and so far all VSO query structures have been assumed to include a time search parameter. It is possible however that some data may not be; model data are an example. As described above, such data would automatically satisfy any time interval query, and at least one additional parameter would be required to make them selectable.)  
     41 
     42'''Observation_Time''' \\  
     43   type: //time// \\ 
     44   FITS keyword: //T_OBS//\\  
     45   The time at which the data comprising an atomic data set were originally recorded. If the duration of the data in the atomic data unit is large compared with the search time resolution, the Observation_Time is to be understood to correspond to the center (mid-point) of the observation(s), weighted as appropriate. For purposes of the Data Model, Observation_Time is given in calendar-clock form, e.g.2004.03.08_16:25. Times are assumed to be UTC. The time resolution is one minute, so for much data the conversion from say start time of an exposure to Observing_Time should not matter. Likewise the conversions between UTC and other units such as ET, TAI, and GPS should not be a matter of much concern. A data match is assumed to include all data from 30 seconds before the target time to 30 seconds after, inclusive (closed at both ends), so that a data Observation_Time can in principle fall into two adjacent target times. Note that since Jan 1, 1999, TAI = UTC + 32 sec, and GPS = UTC + 13 sec.  
     46 
     47'''Duration''' \\ 
     48   type: //number// \\ 
     49   unit: //second// \\ 
     50   FITS keyword: //T_LENGTH// \\  
     51   The interval between the start and end of observation in the atomic data unit. For a single image or spectrum, this is simply the exposure time; for a movie, it is the time difference between the start of the first image and the end of the last. 
     52 
     53'''Time_Step''' \\ 
     54   type: //number// \\ 
     55   unit: //second// \\ 
     56   FITS keyword: //T_STEP// \\ 
     57   The interval between succesive time samples (data records) in a dataset. \\ 
     58 
     59== 2. Target Location == 
     60Target location, by which is meant the spatial location of the target region of imaged or pointed observations on or around the Sun or in the heliosphere, has not yet been built into any VSO query models, although it is a fairly natural selection criterion for observations with a restricted field of view. It may suffice to specify a simple uniform description, although the multi-dimensionality of space makes this harder than one for time. For two-dimensional image data we assume a bounding circle as the simplest model. For this model it is sufficient to specify the center location and radius of the bounding circle. Most real image data are actually described by a bounding rectangle, but this requires specifying at least five parameters (e.g. the coordinates of opposite corners and a position angle).  
     61 
     62'''Observation_Center_West''' \\  
     63   type: //number// \\ 
     64   unit: //arc-second// \\ 
     65   FITS keyword: //CENT_WST// \\ 
     66 
     67'''Observation_Center_North''' \\  
     68   type: //number// \\ 
     69   unit: //arc-second// \\ 
     70   FITS keyword: //CENT_NRT// \\  
     71   A pair of coordinates specifying the location of the center of the image data circle with respect to the Earth-Sun line at the nominal Observation_Time. This origin is close to the center of the apparent solar image for Earth-based or near-Earth observers, but not necessarily for deep space observations. The North coordinate is measured in the direction of the Carrington axis (RA 286°.13, δ 63°.87 J2000.0), and the West coordinate in the direction of solar rotation.  \\ 
     72 
     73'''Bounding_Radius''' \\  
     74   type: //number// \\ 
     75   unit: //arc-second// \\ 
     76   FITS keyword: //R_BOUND// \\ 
     77   The radius of the bounding circle about the Observation_Center. For the VSO Data Model the bounding circle is to be understood as either the maximum inscribed circle in the bounding data rectangle (polygon), or the minimum circumscribed circle, depending on whether the query is for included data (presumably the normal default) or excluded data, respectively.  
     78 
     79== 3. Observer Location == 
     80No Search Parameters have been defined to describe observer location. Two classes of description are appropriate, one for ground-based observations and one for space-based data, particularly in situ measurements. For Earth observatories, a straightforward geographic latitude / longitude / altitude description should suffice, but it is not clear how useful this would be as a discriminator for data searches. For space platforms, where the description of location for in situ data is especially important, we defer to the model (to be) adopted by the VSPO. It should be noted, though, that as stereoscopic imaging of the Sun from space observatories becomes more important, search parameters associated with observer location with respect to solar coordinate frames may have to be introduced. \\ 
     81 
     82== 4. Spectral Range == 
     83The electromagnetic wavelength interval or equivalent over which observations are made is the fundamental discriminator among many types of solar image and other data. The model needs to apply to both narrow-band ("monochromatic" or single-line) and broad-band data. Different branches of the field use different units depending on their spectral band -- frequency at the lowest ranges (of frequency), wavelength at intermediate ranges, energy at the highest. Again for the sake of simplicity we define a single model, assuming that the necessary conversions can be simply made.  
     84 
     85'''Wave_Type''' \\ 
     86   type: //menu// \\ 
     87   FITS keyword: //WV_TYPE// \\  
     88   The class of spectral data, relating to both the nominal spectral bandpass and the spectral target. Three values are recognized: \\ \\ 
     89   '''broad''' 
     90         Indicates that the spectral range of the measurement is large compared to the width of absorption/emission lines within the range, and encompasses multiple lines as well as continuum (unless blanketed).\\ 
     91   '''line''' 
     92         The spectral range of the measurement is of the same order or less than the width of the target line, and is centered on a wavelength within the wings of the line. \\  
     93   '''narrow''' 
     94         The spectral range of the measurement is of the same order or less than the typical width of lines in the neighborhood, but is centered on a continuum wavelength, outside of any significant lines. This designation is used to distinguish narrow-band continuum (or "white-light") data from true broad-band data. For data of this description, the matching spectral range should be much broader than the instrumental bandpass, on the understanding that the data are proxies for broadband measurements. \\ 
     95The exact definition of the bandpass (e.g. FWHM) is not prescribed, but is left up to the terminology of the data provider. In the absence of a provider definition, FWHM should be used. \\ 
     96 
     97'''Wave_Minimum''' \\  
     98   type: //number// \\ 
     99   unit: //Ångström (10nm)// \\  
     100   FITS keyword: //WV_MIN// \\ 
     101 
     102'''Wave_Maximum''' \\  
     103   type: //number// \\ 
     104   unit: //Ångström (10nm)// \\  
     105   FITS keyword: //WV_MAX// \\ 
     106   The nominal minimum (maximum) of the observing spectral bandpass associated with the data. As discussed above, for narrowband continuum data, the range should be much larger than the instrumental bandpass; it should correspond to the spectral range over which the data are useful as a proxy, typically an octave or more. \\ 
     107 
     108'''Wave_Bands''' \\  
     109   type: //number// \\ 
     110   FITS keyword: //WV_NBAND// \\  
     111   The number of wavelength bands in the observation \\ \\ 
     112  
     113'''Wave_Step''' \\  
     114   type: //number// \\ 
     115   unit: //Ångström (10nm) / pixel// \\ 
     116   FITS keyword: //WV_STP// \\ 
     117   The spectral dispersion\\ 
     118  
     119== 5. Observable == 
     120It is in the description of the independent variables, what the data in fact measure, that there is the greatest variation in terminology among data archives. Most solar observational data consist of direct measurements of the intensity of radiation as a function of time, direction (location), wavelength, and polarization, or combinations of intensities associated with different independent variables (e.g. line shifts and splittings, Stokes parameters). These data may be interpreted as measurements of certain physical observables, such as temperature, velocity, emission measure, etc. via models. There are of course some important exceptions: some solar data archives include in situ measurements of such observables as particle fluxes and compositions and magnetic field strengths; some solar data sets represent not direct observation but the results of complex inversions or modeling, such as the frequencies of acoustic modes, or the interior structure; and there are catalogs, histories, and descriptions of features and events. As long as the various observable classes are orthogonal, however, these additional cases should present no problem.  
     121 
     122The model of describing observables in terms of particular combinations of intensity measurements or the associated physical parameters to be derived from them is a natural one for data deriving from imaging spectrographs, such as magnetographs and helioseismic instruments. For cameras or radiometers measuring only intensity or flux at selected wavelengths, it is not so natural. People dealing with data from such instruments tend to think of the observables as being associated with the spectral wavelength or band selected, or for monochromatic instruments, even the spatial-temporal target of the observations. It is important to understand that the meaning of the term "observable" in the VSO Search Parameter model may not at all agree with the meaning of the term as used by the data providers.  
     123 
     124'''Physical_Observable''' \\  
     125   type: //menu// \\ 
     126   FITS keyword: //PHYS_OBS// \\  
     127   The following values are currently recognized: \\ \\ 
     128   '''intensity'''  
     129         the direct intensity, either integrated over the spectral observing range or as a function of wavelength (spectral density)  
     130   '''equivalent_width''' 
     131         differences between intensities measured at nearby wavelengths, typically in line cores, wings, and nearby continuum, whether measured as an intensity difference or an equivalent width  
     132   '''polarization_vector'''  
     133         the net linear polarization  
     134   '''LOS_magnetic_field''' 
     135         the frequency/wavelength Zeeman splitting between opposite circular polarizations of a magnetically-sensitive line  
     136   '''vector_magnetic_field'''  
     137         field strengths and directions inferred from Stokes polarimetry 
     138   '''LOS_velocity'''  
     139         the displacement of line center from rest wavelength/frequency in an arbitrary polarization state  
     140   '''vector_velocity'''  
     141         Two- or three-dimensional velocities, typically inferred from helioseismic inversion or from directly measured velocities transverse to the line of sight, possibly combined with Doppler velocities  
     142   '''wave_power''' \\ 
     143   '''wave_phase''' \\ 
     144   '''oscillation_mode_parameters''' \\ 
     145         These all refer to solar internal or atmospheric acoustic-gravity wave measurements. The mode parameters could include frequencies, splittings, amplitudes, widths, etc.  
     146   '''number_density''' \\ 
     147   '''particle_flux''' \\ 
     148   '''composition'''\\ 
     149   '''particle_velocity'''\\  
     150   '''thermal_velocity''' \\ 
     151        in-situ observations 
     152  
     153In addition to the above, the following classes have been suggested:  
     154* Electric Field Strength - the Stark effect splitting  
     155* Transverse Magnetic Field Strength - Hanle effect measurements  
     156* Stokes Parameters (I, Q, U, V - equivalent to observables of net circular, linear and total polarization, and polarization angle  
     157* //in situ// Magnetic Field  
     158* Differential Emission Measure  
     159* Model Parameters - Interior, Atmosphere, Solar Wind  
     160 
     161== 6. Data Organization == 
     162The data organization describes the physical meaning of the independent variable(s) with respect to which the observables are measured. This is useful for knowing whether and how different data sets can be directly compared, overlaid, mapped, or otherwise transformed. \\ \\ 
     163'''Data_Layout''' \\  
     164   type: //menu// \\ 
     165   FITS keyword: //DATA_ORG// \\  
     166   The following values are recognized: \\ \\ 
     167   '''image'''  
     168         data organized by two dimensions corresponding to angular displacement along the axes; examples include photograms (digital or digitized photographs), spectroheliograms, magnetograms, and Dopplergrams  
     169   '''map'''  
     170         data organized by two dimensions corresponding to spatial displacement along the axes; examples include synoptic charts  
     171   '''time_series'''  
     172         data organized by one dimension corresponding to temporal displacement along the axis; note that this is not the same as a time-tagged set of data records, since it implies sampling uniformity and provision for data gaps  
     173   '''movie'''  
     174         data organized by three dimensions corresponding to spatial or angular displacement along two axes and temporal displacement along the principal (most slowly varying) axis  
     175   '''spectrum'''  
     176         data organized by one dimension corresponding to displacement in electromagnetic wavelength or frequency along the axis  
     177   '''mode_spectrum'''  
     178         data organized by one or more dimensions corresponding to the quantum numbers of oscillations  
     179   '''spectral_temporal'''  
     180         data organized by two dimension corresponding to displacement in wavelength or frequency along one axis and temporal displacement along the other  
     181   '''spatial_spectral'''  
     182         data organized by two dimensions corresponding to spatial or angular image axes and one corresponding to electromagnetic spectral displacement  
     183 
     184== 7. Wave Mode Sampling == 
     185 
     186These parameters relate to data sets derived from helioseismic analysis of solar image data, specifically to global-mode analysis. No such data sets are currently available from any of the providers, so these search parameters have not yet been implemented. \\ \\ 
     187'''Degree_Minimum''' \\ 
     188   type: //number// \\ 
     189   FITS keyword: //L_MIN// \\  
     190'''Degree_Maximum''' \\ 
     191   type: //number// \\ 
     192   FITS keyword: //L_MAX// \\  
     193   The nominal minimum (maximum) of the spherical harmonic degree range associated with the data. \\ 
     194'''Degree_Step''' \\ 
     195   type: //number// \\ 
     196   unit: //Ångström (10nm) / pixel// \\  
     197   FITS keyword: //L_STP// \\ 
     198   The spacing between spherical harmonic degrees in the data  
     199 
     200== 8. Data Source == 
     201 
     202'''Observatory''' \\  
     203      type: //menu// \\ 
     204      FITS keyword: //OBSERVTY// \\  
     205      An identifier of the observatory, space platform, or network of observatories (or spacecraft) from which the data originate. In the case of networks such as GONG or CLUSTER, the particular observatory site or spacecraft may be identified by Instrument if each member is single-instrument. In the case of multi-instrument multi-site networks, another Data Source search parameter (Site or Instance or Platform or Network) may be required. Note that network is used in the sense of functionally identical instruments deployed in different locations, and not coordinated data collections from distinct instruments, such as the H-alpha Network; that is considered a Provider.  
     206      The recognized values are those in the data registry, and the list is subject to modification whenever the data registry is modified. At the time of writing, they include the following:  
     207      * '''BBSO''' : Big Bear Solar Observatory  
     208      * '''Evans''' Solar Telescope, Sacramento Peak  
     209      * '''GONG''' : Global Oscillations Network Group 
     210      * '''JSPO''' : Jeffreys South Pole Observatory  
     211      * '''KANZ''' : Kanzelhöhe Solar Observatory  
     212      * '''KPVT''' : Kitt Peak Vacuum Tower Telescope  
     213      * '''McMath''' Solar Telescope, Kitt Peak  
     214      * '''MEDN''' : Observatoire de Paris, Meudon  
     215      * '''MLSO''' : Mauna Loa Solar Observatory  
     216      * '''MtWilson''' : Mt. Wilson 60ft Tower Telescope  
     217      * '''Nançay''' Radio Observatory  
     218      * '''OACT''' : Osservatorio Astrofisico di Catania  
     219      * '''PicMidi''' : Observatoire du Pic du Midi 
     220      * '''SOHO''' : Solar and Heliospheric Observatory  
     221      * '''SOLIS''' : Synoptic Optical Long-term Investigations of the Sun  
     222      * '''OBSPM''' : Observatoire de Paris, Meudon  
     223      * '''OVRO''' : Owens Valley Radio Observatory  
     224      * '''TON''' : Taiwan Oscillations Network  
     225      * '''YNAO''' : Yunnan Astronomical Observatory  
     226      * '''Yohkoh'''  
     227      For the current list, consult the Registry. \\ 
     228 
     229'''Instrument''' \\  
     230      type: //menu// \\ 
     231      FITS keyword: //INSTRUMT// \\ 
     232      For multi-instrument space observatories, an identifier of the particular instrument from which the data originate. For observatories, the Instrument may refer to a particular telescope or to one of multiple standard configurations of telescope plus detectors. FFor the list of instruments registered, consult the Registry. \\ 
     233'''Provider''' \\  
     234      type: //menu// \\  
     235      The identifier of the data archive providing search and retrieval functions for the data in question. The same data may of course be mirrored at two or more archives. Since the provider id is at least implicit in a data registry, this just means that the same data set would appear in multiple registries. Some data providers may be virtual, that is the query (but not the archive and distribution) services may be handled by other servers with access to their database information as proxies. \\ 
     236      Recognized values at the time of writing:  
     237      * '''HANET''' : H-alpha Network, Big Bear Lake  
     238      * '''HAO''' :High-Altitude Observatory, Boulder  
     239      * '''MSU''' : Montana State University, Bozeman  
     240      * '''NSO''' : National Solar Observatory, Tucson  
     241      * '''OBSPM''' : Observatoire de Paris, Meudon  
     242      * '''OVRO''' : Owens Valley Radio Observatory  
     243      * '''SDAC''' : Solar Data Analysis Center, Greenbelt  
     244      * '''SHA''' : Stanford Helioseismology Archive \\ \\ 
     245      For the current list, consult the Registry  
     246 
     247== 9. Suggestions for Additional Search Parameters == 
     248 
     249The following search parameters or categories are under consideration for possible inclusion in future versions of the VSO Data Model:  
     250* Data processing information - menu?  
     251* Data format - menu? Possible data formats may include: ASCII, FITS, JPEG, GIF, PNG, MPEG, TIFF  
     252 
     253== 10. Nicknames == 
     254 
     255Nicknames for famous combinations od Search Parameters were introduced in Version 1.7 of the Data Model in a separate table. Here they are incorporated in the defining document. Certain problems remain to be resolved. For example, mechanisms are required for designating a logical OR of menu-type parameters, and for specifying whether a Bounding_Radius is an inner radius or an outer radius. \\ \\ 
     256White-light image \\ 
     257   Observable='''intensity''', Data_Layout='''image'''  
     258   Wave_Type={'''broad''' | '''narrow'''} Wave_Minimum≥'''3000''', Wave_Maximum≤'''10000'''  
     259coronagraph image  
     260   Observable='''intensity''', Data_Layout='''image'''  
     261   |Observation_Center_West|≤'''20''', |Observation_Center_North|≤'''20''', Bounding Radius≥'''950''' (excluded)  
     262H-alpha image  
     263   Observable='''intensity''', Data_Layout='''image''' 
     264   Wave_Type='''line''', Wave_Minimum≥'''6558''', Wave_Maximum≤'''6568'''  
     265Ca-K image  
     266   Observable='''intensity''', Data_Layout='''image''' 
     267   Wave_Type='''line''', Wave_Minimum≥'''3919''', Wave_Maximum≤'''3952'''  
     268He 10830 image  
     269   Observable='''intensity''', Data_Layout='''image''' 
     270   Wave_Type='''line''', Wave_Minimum≥'''10825''', Wave_Maximum≤'''10833''' 
     271Na-D image  
     272   Observable='''intensity''', Data_Layout='''image''' 
     273   Wave_Type='''line''', Wave_Minimum≥'''5888''', Wave_Maximum≤'''5898'''  
     274Hard X-ray image 
     275   Observable='''intensity''', Data_Layout='''image'''  
     276   Wave_Minimum≥'''0.2''', Wave_Maximum≤'''10''',  
     277Soft X-ray image  
     278   Observable='''intensity''', Data_Layout='''image''' 
     279   Wave_Minimum≥'''5''', Wave_Maximum≤'''150''',  
     280EUV image  
     281   Observable='''intensity''', Data_Layout='''image''' 
     282   Wave_Minimum≥'''100''', Wave_Maximum≤'''1250''',  
     283UV image  
     284   Observable='''intensity''', Data_Layout='''image''' 
     285   Wave_Minimum≥'''900''', Wave_Maximum≤'''3800''',  
     28610.7 cm image  
     287   Observable='''intensity''', Data_Layout='''image''' 
     288   Wave_Type='''narrow''', Wave_Minimum≥'''1.06*10^9^''', Wave_Maximum≤'''1.08*10^9^''',  
     289Continuum image  
     290   Observable='''intensity''', Data_Layout='''image'''  
     291   Wave_Type='''narrow'''  
     292Full-disk magnetogram  
     293   Wave_Type='''line''', Data_Layout='''image'''  
     294   Observable={ '''LOS_magnetic field''' | '''vector_magnetic field''' }  
     295   |Observation_Center_West|≤'''20''', |Observation_Center_North|≤'''20''', Bounding Radius≥'''800'''  
     296LOS magnetogram  
     297   Observable='''LOS_magnetic field''', Data_Layout='''image'''  
     298   Wave_Type='''line''' 
     299vector magnetogram  
     300   Observable='''vector_magnetic field''', Data_Layout='''image'''    
     301   Wave_Type='''line'''  
     302Full-disk dopplergram  
     303   Observable='''LOS_velocity''', Data_Layout='''image'''  
     304Wave_Type=line  
     305   |Observation_Center_West|≤'''20''', |Observation_Center_North|≤'''20''', Bounding Radius≥'''800'''  
     306Na-D dopplergram, Data_Layout='''image'''  
     307   Observable='''LOS_velocity''', Data_Layout='''image'''  
     308   Wave_Type='''line''', Wave_Minimum≥'''5888''', Wave_Maximum≤'''5898'''  
     309Ni-6768 dopplergram  
     310   Observable='''LOS_velocity''', Data_Layout='''image'''  
     311   Wave_Type='''line''', Wave_Minimum≥'''6767''', Wave_Maximum≤'''6769''' 
     312K-7699 dopplergram  
     313   Observable='''LOS_velocity''', Data_Layout='''image''' 
     314   Wave_Type='''line''', Wave_Minimum≥'''7698''', Wave_Maximum≤'''7700'''  
     315EUV Spectrum  
     316   Observable='''intensity''', Data_Layout='''spectrum'''  
     317   Wave_Type='''broad''', Wave_Minimum≥'''100''', Wave_Maximum≤'''1250''' 
     318UV Spectrum  
     319   Observable='''intensity''', Data_Layout='''spectrum'''  
     320   Wave_Type='''broad''', Wave_Minimum≥'''900''', Wave_Maximum≤'''3800''' 
     321Visible Spectrum  
     322   Observable='''intensity''', Data_Layout='''spectrum'''  
     323   Wave_Type='''broad''', Wave_Minimum≥'''3500''', Wave_Maximum≤'''10000''' 
     324IR Spectrum  
     325   Observable='''intensity''', Data_Layout='''spectrum'''  
     326   Wave_Type='''broad''', Wave_Minimum≥'''7000''', Wave_Maximum≤'''3.5*10^6^'''  
     327Atlas Spectrum  
     328   Observable='''intensity''', Data_Layout='''spectrum'''  
     329   Wave_Type='''broad (?)'''  
     330Helioseismic Time series  
     331   Observable={ '''wave_power''' | '''wave_phase''' | '''oscillation_mode_parameters''' }  
     332Light Curve Time series  
     333   Observable='''intensity''', Data_Layout='''time_series''' 
     334 
     335 
     336 
     337 
     338 
     339