NcML is an XML representation of netCDF metadata, (approximately) the header information one gets from a netCDF file with the "ncdump -h" command. NcML is similar to the netCDF CDL (network Common data form Description Language), except, of course, it uses XML syntax.
NcML development is happening on two fronts:
The simplest use of NcML is to describe the metadata and structural content of a netCDF file, like the output of ncdump -h. There are several ways to generate NcML ouput from an existing netCDF file:
java -classpath toolsUI.jar ucar.nc2.NCdump <NetCDF-3 filename> -ncml
Using the NetCDF-Java library, you can also use NcML to create a new netCDF-3 file, similar to the ncgen program.
A more advanced use is to modify existing NetCDF files, as well as to create "virtual" NetCDF datasets, for example through aggregation. In that case, you'll have to read more:
Earlier work in defining XML representations for netCDF data included Bear Giles DTD and XML tools in March 2000, a proposed DTD by Stefano Nativi and Lorenzo Bigagli at the University of Florence in May 2000, and a version developed by John Caron in February 2001.
The original NcML working group consisted of John Caron (Unidata/UCAR), Luca Cinquini (SCD/NCAR), Ethan Davis (Unidata/UCAR), Bob Drach (PCMDI/LLNL), Stefano Nativi (University of Florence), and Russ Rew (Unidata/UCAR).
In the first implementation of NcML (version 2.1), there were three parts to NcML with separate schema documents: 1) NcML Core Schema represented the existing netCDF-3 data model; 2) NcML Coordinate System extended NcML Core Schema and extended the netCDF data model to add explicit support for general and georeferencing coordinate systems; 3) NcML Dataset extended NcML Core Schema to use NcML to define a netCDF file, similar to the ncgen command line tool, as well as to redefine, aggregate, and subset existing netCDF files.
NcML Coordinate System is now superceded by NcML-GML.
NcML Core Schema and NcML Dataset have been combined into a single NcML Schema, and some of the NcML Dataset syntax and functionality has been modified.
Please send comments and/or questions to firstname.lastname@example.orgThis document is maintained by John Caron and was last updated on Nov 2010