| 1 | === Properties === |
| 2 | |
| 3 | Properties recognised by the CF data model correspond to attributes listed in the CF for NetCDF files: Appendix A. |
| 4 | |
| 5 | * standard_name |
| 6 | * a controlled vocabulary - the value must be a valid vocabulary item (http://cf-pcmdi.llnl.gov/documents/cf-standard-names/) |
| 7 | * valid for: |
| 8 | * field |
| 9 | * dimension coordinate |
| 10 | * auxiliary coordinate |
| 11 | * cell measure |
| 12 | * units |
| 13 | * a controlled vocabulary - the value must be a valid vocabulary item (http://www.unidata.ucar.edu/software/udunits/)names/) |
| 14 | * valid for: |
| 15 | * field |
| 16 | * dimension coordinate |
| 17 | * auxiliary coordinate |
| 18 | * cell measure |
| 19 | * comment |
| 20 | * valid for: |
| 21 | * field |
| 22 | * history |
| 23 | * valid for: |
| 24 | * field |
| 25 | * institution |
| 26 | * valid for: |
| 27 | * field |
| 28 | * long_name |
| 29 | * valid for: |
| 30 | * field |
| 31 | * dimension coordinate |
| 32 | * auxiliary coordinate |
| 33 | * cell measure |
| 34 | * references |
| 35 | * valid for: |
| 36 | * field |
| 37 | * source |
| 38 | * valid for: |
| 39 | * field |
| 40 | * standard_error_multiplier |
| 41 | * valid for: |
| 42 | * field |
| 43 | * title |
| 44 | * valid for: |
| 45 | * field |
| 46 | * axis |
| 47 | * In a field, a given value of the axis attribute can occur no more than once among all the dimension and auxiliary coordinates of that field. |
| 48 | * valid for: |
| 49 | * dimension coordinate |
| 50 | * auxiliary coordinate |
| 51 | * calendar |
| 52 | * valid for: |
| 53 | * dimension coordinate |
| 54 | * auxiliary coordinate |
| 55 | * leap_month |
| 56 | * valid for: |
| 57 | * dimension coordinate |
| 58 | * auxiliary coordinate |
| 59 | * leap_year |
| 60 | * valid for: |
| 61 | * dimension coordinate |
| 62 | * auxiliary coordinate |
| 63 | * month_lengths |
| 64 | * valid for: |
| 65 | * dimension coordinate |
| 66 | * auxiliary coordinate |
| 67 | * positive |
| 68 | * valid for: |
| 69 | * dimension coordinate |
| 70 | * auxiliary coordinate |
| 71 | * climatology |
| 72 | * valid for: |
| 73 | * dimension coordinate |
| 74 | * auxiliary coordinate |
| 75 | |
| 76 | |
| 77 | |
| 78 | The attributes |
| 79 | * valid_max |
| 80 | * valid_min |
| 81 | * valid_range |
| 82 | 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. |
| 83 | |
| 84 | The attributes |
| 85 | * _FillValue |
| 86 | * missing_value |
| 87 | 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. |
| 88 | ''question: is this the case for coords too, auxiliary coords may contain missing data, I believe.'' |
| 89 | |
| 90 | The attributes |
| 91 | * add_offset |
| 92 | * compress |
| 93 | * flag_masks |
| 94 | * flag_meanings |
| 95 | * flag_values |
| 96 | * scale_factor |
| 97 | 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). |
| 98 | |
| 99 | The 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. |
| 100 | |
| 101 | The attributes: |
| 102 | * bounds |
| 103 | * cell_measures |
| 104 | * cell_methods |
| 105 | * climatology |
| 106 | * Conventions |
| 107 | * coordinates |
| 108 | * formula_terms |
| 109 | * grid_mapping |
| 110 | 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. These attributes do not correspond to properties in the data model and should not be used ouside the context of CF-NetCDF. |
| 111 | |
| 112 | |
| 113 | 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. Since they are not part of the CF standard, the data model does not provide any interpretation of them. |
| 114 | ''Question: can cell_measures, cell_methods use non-conflicting attributes?'' |
| 115 | |
| 116 | |