| netCDF properties | cfa_array attributes | Partitions attributes | subarray attributes |
|---|---|---|---|
| cf_role, cfa_dimensions, cfa_array | Partitions, pmdimensions, pmdimensions, pmshape, base, | index, location, pdimensions, reverse, subarray, punits, pcalendar, part, | shape, file, dtype, ncvar, varid, file_offset, format |
This standard CF property must be used to mark the netCDF variable as either an CFA variable or a CFA private variable.
It takes values of "cfa_variable" or "cfa_private" for a CFA variable or CFA private variable respectively.
| Examples | |
|---|---|
| "cfa_variable" | |
| "cfa_private" |
A netCDF property whose value is a string containing the ordered, space delimited set of the master array’s dimension names. The specified dimensions are all defined as netCDF dimensions in the CFA-netCDF file.
If missing, an empty sting or a string containing only spaces then the master array is assumed to be scalar.
| Examples | |
|---|---|
| "time lat lon" | |
| "" | |
| " " |
The master array’s dimensions are stored outside of the cfa_array property in order to provide useful information about the master array without having to decode the cfa_array string (which may not be possible in all APIs).
A netCDF property whose value is a JSON encoded associative array containing the attributes required for constructing the aggregated data array.
The dimensions, shape, dtype, units and calendar master data array parameters are specified elsewhere (by properties of the netCDF CFA variable or inferrable from the netCDF dimensions in CFA-netCDF file) and so are not required.
The encoded string may be relatively succinct, as many attributes have well defined default values.
| Examples | |
|---|---|
| '{"Partitions":[{"index": [0], "subarray": {"file": "test1.nc", "shape": [64, 128], "ncvar": "tas"}, "location": [[0, 64], [0, 128]]}]}' |
The JSON decoded attributes are described here:
An ordered list of strings containing the names of the dimensions of the partition martrix. Each of these dimensions is one those specified by the cfa_dimensions property (and is therefore defined as a netCDF dimension in the CFA-netCDF file).
The value [] means that the partition matrix is a scalar, i.e. the master array comprises a single partition.
If missing then it is assumed that the partition matrix is a scalar.
| Examples | |
|---|---|
| ["lat", "time"] | |
| ["height"] | |
| [] |
An ordered list of integers containing shape of the partition matrix. The integers sizes correspond to the dimensions of the partition matrix given by pmdimensions.
The value [] means that the partition matrix is a scalar, i.e. the master array comprises a single partition.
If missing then it is assumed that each dimension of the partition matrix has size 1. For example, if pmdimensions is [] then the default shape is [] and if pmdimensions is ["time", "height"] then the default shape is [1, 1].
| Examples | |
|---|---|
| [2, 3] | |
| [87] | |
| [1, 1] | |
| [1] | |
| [] |
A string giving the base for relative file names given by file. May be an absolute or relative URL or location on the local system. If it is a relative location then it assumed to be relative to the local directory or URL base containing the CFA-netCDF file.
If set then all file names are assumed to have relative paths. If it is an empty string ("") then the base is taken as the local directory or URL base containing the CFA-netCDF file.
If missing then it is assumed that all file names are absolute paths (local files or URLs).
| Examples | |
|---|---|
| "/data/archive" | |
| "../archive/" | |
| "http://archive/files" | |
| "" |
A list whose elements define each of the master array’s partitions. The order of the list is arbitrary since each element contains its (possibly multidimensional) index in the partition matrix.
| Examples | |
|---|---|
| [{"index": [0], "subarray": {"shape": [2, 3], "ncvar": "cfa_1bE8EBC2c3"}, "location": [[0, 1], [0, 2]]}] |
Each element of the list is an associative array which specifies a partition with the following attributes:
- index
An ordered list of indices specifying the position of the partition in the partition matrix. The indices correspond to the pmdimensions list.
An index of [] means that the partition matrix is a scalar, i.e. the master array comprises a single partition.
If missing then it is assumed that the master array comprises a single partition.
Examples [0] [2, 1] [] Note
Indices count from zero.
- location (optional)
An ordered list of ranges of indices, one for each dimension of the master data array, which describe the contiguous section of the master data array spanned by the partition’s data array. The ranges correspond to the cfa_dimensions list.
Each range is a two-element list giving a start and stop index for its dimension. For example, the range [3, 5] is equivalent to indices 3, 4 and 5; and the range [6, 6] is equivalent to index 6.
If the master data array is a scalar then it may be an empty list.
If missing then it is assumed that the partition matrix contains exactly one partition whose data array spans the entire master array.
Examples [[2, 2], [3, 5], [2, 56]] [[0, 0]] [] Note
Indices count from zero.
- pdimensions (optional)
An ordered list of the partition’s sub-array dimension names. The specified dimensions are all defined as netCDF dimensions in the CFA-netCDF file.
If there are any size 1 dimensions of the partition which are not spanned by the master array then the partition’s dimensions must be specified.
If the partition’s data array is a scalar then it may be an empty list.
If missing then it is assumed to be equal to dimensions of the master array.
Examples ["lon", "time", "lat"] [] Note
If a partition’s data array dimensions are not specified and the sub-array is stored in another file then it is required only that the sub-array has the same number of dimensions, with the same physical meaning and in the same order as the master array. For example, if the sub-array were in a different netCDF file, its dimensions may have different names and sizes relative to the equivalent dimensions in the CFA-netCDF file.
- reverse (optional)
An arbitrarily ordered list of zero or more of the partition’s data array dimension names. The specified dimensions are all defined as netCDF dimensions in the CFA-netCDF file.
Each specified dimension of the partition’s sub-array is assumed to run in the opposite direction to the master data array and so will need to be reversed prior to use within the master data array.
If missing, or an empty list, then it is assumed that no partition sub-array dimensions need to be reversed.
Examples ["time"] ["lon", "time", "lat"] []
- punits (optional)
A string containing the units of the partition’s data array.
If missing then it is assumed to be equal to units of the master array.
Examples "m s-1" "days since 2000-12-1" "1" ""
- pcalendar (optional)
A string containing the calendar of the partition’s units.
If missing then it is assumed to be equal to calendar of the master array.
Examples "noleap"
- part (optional)
A string defining the part of the partition’s sub-array which comprises the partition’s data array.
For each of the partition’s dimensions, the string describes the indices of the sub-array which define the partition’s data array. The indices correspond to to the pdimensions list.
Indices are contained within round or square brackets. Round brackets specify a sequence of indices along that dimension. Square brackets provide a succinct method of describing a strictly monotonic and regularly spaced sequence of indices for the dimension via start, stop and step values. For example, [0, 3, 1] is equivalent to (0, 1, 2, 3) and [10, 4, -2] is equivalent to (10, 8, 6, 4).
If missing, or the string "[]", then it is assumed that the partition’s data array spans the entire sub-array.
Examples "[[2, 5, 1], (1, 3, 4, 7), [0, 11, 2]]" "[(4, 2, 1), [5, 1, -4], [0, 0, 1]]" "[]" Note
Indices count from zero.
- subarray
An associative array giving the attributes required to define the sub-array containing the partition’s data array. Only a subset of these will be required, depending on the storage format of the sub-array.
Examples {"shape": [4, 7, 3], "ncvar": "cfa_345eA9001D", "varid": 10} {"file": "temp.nc", "ncvar": "tas", "shape": [1200], "format": "netCDF"} {"dtype": "float", "file": "temp.nc", "shape": [1200], "varid": 6} {"shape": [73, 96], "file": "../data.pp", "file_offset": 7348, "format": "PP"} {"shape": [73, 96], "file": "data.pp", "file_offset": 0, "format": "PP"} The keys specify a sub-array with the following attributes:
- format (optional)
A string naming the format of the file containing the partition’s sub-array.
If missing then the format is assumed to the same as the CFA-netCDF file.
Examples "netCDF" "PP"
- shape
An ordered list of the partition’s sub-array dimension sizes. The sizes correspond to to the pdimensions list.
Examples [4, 7, 3] [1, 1] []
- file (optional)
A string naming the file which contains the partition’s sub-array. May be a local file or a URL.
If base has been set then the file name is assumed to be relative to it. If base is an empty string ("") then the base is taken as the local directory or URL base containing the CFA-netCDF file.
If base has not been set then the file name is assumed to be an absolute path (local file or URL).
If missing or an empty string ("") then it is assumed to be the CFA-netCDF file itself.
Examples "/home/me/file.nc" "../file2.pp" "file3.nc" "http://archive/data/file.nc" "data/file.nc" ""
- dtype (optional)
The data type of the partition’s sub-array. Any of the netCDF data type strings are allowed.
If missing then the data type of the master array is assumed.
Examples "double" "byte" "char"
- ncvar (for netCDF files only, optional)
A string containing the name of the netCDF variable containing the partition’s sub-array.
Examples "tas" "latitude" "cfa_678df4g745" If missing then the varid attribute must be set.
If both the ncvar and varid attributes are set then varid is ignored.
- varid (for netCDF files only, optional)
The integer UNIDATA netCDF interface ID of the variable containing the partition’s sub-array.
Examples 24 0 If missing then the ncvar attribute must be set.
If both the ncvar and varid attributes are set then varid is ignored.
- file_offset (not required for netCDF files)
The non-negative integer byte address of the file where the metadata of the partition’s sub-array begins. The start of the file is addressed by zero.
Examples 0 8460364