Extracts the license annotation from the metadata annotation of thenexml
object, and returns its value.
get_license(nexml)the license if the metadata asserts one that is non-empty, and NA otherwise.If multiple non-empty annotations are found, only the first one is returned.
a nexml object
Currently the implementation looks for cc:license and dc:rights
annotations. (Note that these may be given with any prefix in the metadata
so long as they expand to the same full property URIs.)
get_metadata_values()