If a CSV or XLS file contains X/Y or Lat/Long attributes the reader will allow reading those fields into a geometry.
The next step would be to allow a spatial predicate in the FeatureReader transformer.
The current FeatureReader does not allow spatial selection on these formats and forces you to use the Clipper transformer to select features inside the area of interest.
This could be hidden in the FeatureReader for datasets containing coordinate information.
