Added permission to fill empty data when slicing a sparse dimension (#…

…105)

standard/clause_9_coverage_rangesubset_subset_and_scaling.adoc

@@ -8,6 +8,10 @@ The subset parameter is defined in the following Requirement:
 
 include::requirements/coverage-subset/REQ_cov-subset-definition.adoc[]
 
+The following permission is granted to facilitate slicing data sparsely populated across a dimension, such as Earth Observation imagery:
+
+include::recommendations/coverage-subset/PER_slice-sparse-dimensions.adoc[]
+
 The results of using a subset parameter are defined by the following Requirement:
 
 include::requirements/coverage-subset/REQ_cov-subset-success.adoc[]

standard/recommendations/coverage-subset/PER_subset-slice-dimensions.adoc

@@ -0,0 +1,12 @@
+[[per_slice_sparse_dimension]]
+[width="90%",cols="2,6a"]
+|===
+^|*Permission {counter:per-id}* |*/per/coverage-subset/slice-sparse-dimension*
+^|A |The empty portions of a slice operation on an axis (e.g. time), combined with a trimming operations on other axes (e.g. latitude and longitude)
+ which would either be empty or not cover the full extent of the trim operation MAY be filled with data values from the same trim operation
+ combined with a slicing operation on a different value of the slicing axis which would return non-empty values.
+ For example, the closest or last previous time for which data is available for a certain geospatial extent may be returned.
+ An Earth Observation use case for this permission is to allow retrieving a slice of the last available imagery on or before a certain date,
+ taking into account that a certain geographic area may only be observed every few days.
+^|B |A query parameter defined by a custom or standardized extension MAY be made available to disable or change that behavior.
+|===