Merge pull request #52 from jyucsiro/nc2rdf

Proposing a command line tool nc2rdf

Author: jyucsiro

nc2rdf/README.md

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+# nc2rdf
+
+This tool allows users to input CDL or netCDF files and get an RDF graph returned.
+
+Example:
+```
+$ python nc2rdf.py  ../lib/bald/tests/integration/CDL/array_alias.cdl
+```
+
+By default, nc2rdf tries to detect CDL and nc files using the file suffix. Output by default is
+RDF N3 triples.
+
+Users can specify CDL files using the `--cdl` option.
+```
+$ python nc2rdf.py --cdl myfile.cdl
+```
+
+Users can specify netCDF files usings the `--nc` ioption.
+```
+$ python nc2rdf.py --nc myfile.nc
+```
+
+More info, refer to the help option
+```
+$ python nc2rdf.py -h
+```
+
+Other outputs include TTL and XML
+```
+$ python nc2rdf.py -o ttl myfile.nc
+$ python nc2rdf.py -o xml myfile.nc
+```
+
+Note: This command-line tool is experimental and is subject to changes, however serves as a prototype for accessing bald functions for netCDF related files to RDF.

nc2rdf/nc2rdf.py

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+import argparse
+import os
+import subprocess
+import tempfile 
+import netCDF4
+import numpy as np
+import bald
+
+def nc2rdf(ncfilename, outformat):  
+    #print("nc2rdf test")
+    #print(ncfile)
+    root_container = bald.load_netcdf(ncfilename)
+    ttl = root_container.rdfgraph().serialize(format=outformat).decode("utf-8")
+    print(ttl)
+
+def cdl2rdf(cdl_file, outformat): 
+    #print("cdl2rdf test")
+    #print(cdl_file)
+    tfile, tfilename = tempfile.mkstemp('.nc')
+    #print(tfilename)
+    subprocess.check_call(['ncgen', '-o', tfilename, cdl_file])
+
+    nc2rdf(tfilename, outformat)
+
+    os.close(tfile)
+    os.remove(tfilename)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description='Convert netCDF metadata to RDF.')
+    parser.add_argument('-o', action="store", dest="format", default='n3', help="RDF output format (n3 *default, ttl, xml)")
+    parser.add_argument('--cdl', action="store_true", dest="isCDL", default=False, help="Flag to indicate file is CDL")
+    parser.add_argument('--nc', action="store_true", dest="isNC", default=False, help="Flag to indicate file is netCDF")
+    parser.add_argument("ncfile", help="Path for the netCDF file")
+
+    args = parser.parse_args()
+
+    if(args.isCDL or args.ncfile.endswith(".cdl") or args.ncfile.endswith('.CDL')):
+        cdl2rdf(args.ncfile, args.format)
+    elif(args.isNC or args.ncfile.endswith(".nc") or args.ncfile.endswith('.NC')):
+        nc2rdf(args.ncfile, args.format)
+    else:
+        print("Unrecognised file suffix. Please indicate if CDL or NC via --cdl or --nc");