A view of the sampling feature with some subset of the constrained observations, where the result set is a trend over the sampled time envelope. SamplingSite implements a characterisation of the Feature of Interest, through a set of observations. The key implication is that the location of the site and the observation procedures provides for a representative sample of the actual feature, within the scope of the sampling regime (e.g. a time period) This is a view of the sampling feature that contains no observations, and can be used simply to map the spatial location, access identify and metadata etc. Externally defined vocabulary of common phenomenon codes