Introducing CDL (Common Data Language)

4.9 Introducing CDL (Common Data Language)

CDL (Common Data Language) is text notation for netCDF objects and data. It will be used for examples during the workshop.

  netcdf example {   // example of CDL notation
  dimensions:
	  x = 3 ;
	  y = 8 ;
  variables:
	  float rh(x, y) ;
		  rh:units = "percent" ;
		  rh:long_name = "relative humidity" ;
  // global attributes
	  :title = "simple example, lacks some conventions" ;
  data:
   rh =
    2, 3, 5, 7, 11, 13, 17, 19,
    23, 29, 31, 37, 41, 43, 47, 53,
    59, 61, 67, 71, 73, 79, 83, 89 ;
  }

This example specifies a netCDF dataset with two dimensions (x and y), one variable (rh), two variable attributes (units and long_name), one global attribute (title), and some data values for the variable.

This example has only one variable, but multiple variables may be included in a netCDF file.
CDL comments follow "//" symbols. They are not part of netCDF data. To store comments about a variable or file, use a variable attribute or global attribute.
You can use the ncdump utility to get the CDL form of a binary netCDF file (more on this later).
You can use the ncgen utility to generate a binary netCDF file from CDL (more on this later).
This simple example neglects some recommended best practices for netCDF data.
NcML is an XML-based notation similar to CDL for netCDF data

2010 Unidata NetCDF Workshop > The Two NetCDF Data Models