Propagation of specific extensions may also be inhibited by specifying `NOEXTENSION()' in the CLIST argument to NDF_PROP and listing the extensions to be omitted between the parentheses. For instance:
CALL NDF_PROP( INDF1, 'Axis,Noext(IRAS,ASTERIX)', 'OUT', INDF2, STATUS )
would force propagation of the axis components, but inhibit the propagation of any `IRAS' or `ASTERIX' extension which may be present. Note that `NOEXTENSION' may be abbreviated but extension names must appear in full, although mixed case is permitted.
This mechanism can be useful if an extension may contain a large amount of information but is not required in the output data structure. The alternative (of propagating the extension, then deleting it) is less efficient and may lead to an unnecessarily large output file.
An asterisk may be used to indicate ``all extensions''. Thus
CALL NDF_PROP( INDF1, 'Axis,Noext(*)', 'OUT', INDF2, STATUS )
would inhibit the propagation of all extensions. Likewise,
CALL NDF_PROP( INDF1, 'Axis,Noext(*),Ext(IRAS)', 'OUT', INDF2, STATUS )
would propagate just the IRAS extension.