at the first rule checks the variable <code>CL_FREQ</code> against a code list
that is retrieved from the global SDMX registry. A demonstration of the fact
that a DSD does not have to be fully self-contained and can refer to
metadata in other standard registries. If a data set is checked against this
rule, <code>validate</code> will download the codelist from the global registry and
compare each value in column <code>CL_FREQ</code> against the codelist.</p>
<p>Note that the <code>validator_from_dsd</code> f