Our instances are obviously XML and there are no such thing of instance of logical model (instance of logical model would be a physical model, such as XML). The first clause is odd at best, because using a URL to denote a property is encoding specific (and I would say almost XML specific). I fixed the URL in the logical model because it does not have any impact on XML clauses and this is what we did in our instance examples.
In the logical model, we say - use the requirement URL
_SFSamplingFeatureComplex:role for the sampling feature where the test is performed SHALL have the value http://www.opengis.net/req/aquifertest/testfeature
but in the XML encoding we say, use a defined term from GWML vocab
_SF_SamplingFeatureComplex roles that associates GWAquiferTest with test features SHALL have it’s xlink:href set to http://resource.gwml.org/def/role/testFeature
Our instances are obviously XML and there are no such thing of instance of logical model (instance of logical model would be a physical model, such as XML). The first clause is odd at best, because using a URL to denote a property is encoding specific (and I would say almost XML specific). I fixed the URL in the logical model because it does not have any impact on XML clauses and this is what we did in our instance examples.