Changes between Initial Version and Version 1 of Ticket107Text9Nov13Properties

11/09/13 14:39:26 (7 years ago)



  • Ticket107Text9Nov13Properties

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     1The other properties recognised by this CF data model correspond to attributes listed in CF Appendix A. For field constructs, the allowed properties are `comment`, `history`, `institution`, `long_name`, `references`, `source`, `standard_error_multiplier`, `standard_name`, `title`, `units`. For dimensions and auxiliary coordinate constructs, the allowed properties are `axis`, `calendar`, `leap_month`, `leap_year`, `long_name`, `month_lengths`, `positive`, `standard_name`, `units`. Coordinate constructs of time are optionally climatological; this property is indicated by the presence of the `climatology` attribute. In any field, any given value of the `axis` attribute can occur no more than once among all the dimension and auxiliary coordinates of that field. The CF data model allows field, dimension and auxiliary coordinate constructs to have other properties not defined by CF, provided they do not conflict with CF, but since they are not part of the CF standard, the data model does not provide any interpretation of them.
     3The attributes `valid_max`, `valid_min` and `valid_range` of data variables and coordinate variables are checks on the validity of the values, which could be verified on input and written on output. In this CF data model we assume they do not constrain any manipulations which might be done on the data in memory, and they are not part of the data model.
     5The attributes `_FillValue` and `missing_value` of data variables specify how missing data is indicated in the data array. This data model supports the idea of missing data, but does not depend on any particular method of indicating it, so these attributes are not part of the model.
     7The attributes `add_offset`, `compress`, `flag_masks`, `flag_meanings`, `flag_values` and `scale_factor` are all used in methods of compressing the data to save space in CF-netCDF files, with or without loss of information. They are not part of this data model because these operations do not logically alter the data, except that the `compress` attribute implies two alternative interpretations of coordinates (compressed or uncompressed).
     9The `featureType` attribute and associated conventions provide a way of packing multiple fields of the same kind of discrete sampling geometry (timeseries, trajectories, etc.) into a single CF-netCDF data variable, in order to save space, since a multidimensional representation with common coordinate variables is typically very wasteful in such cases. This is a kind of compression. The data model regards each instance of the feature type as an independent field construct. The `featureType` attribute is a property of each of these field constructs.
     11The attributes `bounds`, `cell_measures`, `cell_methods`, `climatology`, `Conventions`, `coordinates`, `formula_terms` and `grid_mapping` have various special or structural functions in the CF-netCDF file format. Their functions and the relationships they indicate are reflected in the structure of this data model, and these attributes do not correspond directly to properties in the data model.