WCPS-Manual / subsetExpr
The subsetExpr element specifies spatial and temporal domain subsetting. It encompasses spatial and temporal trimming (i.e. constraining the result coverage domain to a subinterval, slicing (i.e. cutting out a hyperplane from a coverage) extending and scaling of a coverage expression.
All of the subsetExpr elements allow to make use of coordinate reference systems other than a coverage's image CRS. A coverage's individual mapping from general domain to image CRS (grid cell) coordinates does not need to be disclosed by the server, hence any coordinate transformation should be considered a "black box" by the client.
Note: The special case that subsetting leads to a single cell remaining still resembles a coverage by definition; this coverage is viewed as being of dimension 0.
Note: Range subsetting is accomplished via the unary induced fieldExpr.