ISTP/IACG Dictionary Keywords

A project data dictionary contains information required to make the data independently useable to a wide community. For ISTP/IACG the Common Data Format (CDF), chosen as the data exchange format for key parameter and event data, carries much (but not all) of the data dictionary information using a set of standard global attributes describing the overall CDF content and a set of standard attributes for each variable in the CDF. The variable attributes contain descriptions, data types, minimum and maximum values, labels, units, time tags, and if required, dependencies, uncertainties, and offsets. However there is little consistency in variable names nor in the descriptions that are tied to each variable, to help other users of the data find and use the variables of interest. We have extended the ISTP/IACG project data dictionary to include dictionary keywords that identify variables as being a certain type such as time or magnetic_field regardless of the naming convention adopted by the investigators. Each variable in a CDF has defined dictionary keywords (class and subclass) that are stored in its associated DICT_KEY attribute.

List of Class Keywords

We provide a standard set of class keywords that include `sensor (science)' and `supporting' class words and their meanings, to be used to categorize the data variables of primary interest to investigators, among the several ISTP/IACG satellites and experiments. ISTP/IACG class keywords will be restricted to the approved values shown below. Sets of subclass keywords, with each set used to modify one of the class keywords, are also adopted and listed with the associated information below. Lists of common subclass keywords, valid for any variable, can also be found below.

Sensor Words                                Supporting Words

anisotropy                                  angle
current                                     energy
density                                     flag
electric_field                              frequency
magnetic_field                              label
particle_flux                               number
photon_flux                                 ratio
position                                    significance
potential                                   source
power                                       species
pressure                                    time
temperature                                 uncertainty
velocity                                    wavelength

Common subclass keywords valid for any variable

Implementation

The syntax for populating the Dictionary Keyword attribute DICT_KEY is class>subclass_subclass_subclass. Click here for examples.

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ISTP/IACG Dictionary Keywords (in Postscript format).

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Associated information : More on Class words

The dictionary keywords and definitions (along with the other global and variable attributes) comprise the primary content of the ISTP/IACG project data dictionary. The class keywords were selected to be, as much as possible, a complete and orthogonal set. In the realm of space physics there are three broad classes of sensor data words: electric and magnetic field (DC values for vectors, AC values for power spectra), particle distributions (e.g., densities, flow speeds, flow direction angles, thermal speeds, temperatures, anisotropy, fluxes), images (e.g., remote sensing of the aurora, ionosphere and sun at various wavelength ranges measuring e.g., electromagnetic waves, temperatures, pressures). In addition, there are time words, orbit/attitude words, and flags of various types (e.g.,instrument mode). We choose the measured quantities such as magnetic_field, density, temperature, to be the sensor (science) class keywords that are of primary science interest. Supporting keywords are of secondary science interest such as the energy or time at which a measurement was made, or the label or flag associated with a measured quantity. The sensor (science) class words are listed separately from the supporting class words below. It is envisioned that the usage of the sensor (science) and supporting class keywords will be different. Sensor Words make up a short, standard list that enables automated searching for data of interest at a fairly high level. Supporting Words are at a lower level of interest, but may still be used for some types of searches. In the CDF model every variable must have one and only one class keyword defined, but may have any number of subclass keywords defined.

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Class word definitions and associated subclass words

ANGLE The geometric figure formed by two lines diverging from a point or two planes diverging from a common line or the space between two such lines or surfaces.


Subclass Words        antenna       elevation      pitch
                      aspect        fov            pointing
                      axis          geometric      polar
                      azimuth       inclination    rotation
                                    phase          sector