20                 if (args.length != 3) {
 
   21                         throw new ValueExprEvaluationException(getURI() + 
" requires exactly 1 arguments, got " + args.length);
 
   23                 LiteralType l=LiteralRegistry.getLiteral(((Literal)args[0]).getDatatype().toString());
 
   24                 if(l instanceof RasterLiteral) {
 
   25                         GridCoverage geom=((RasterLiteral)l).read(args[0].stringValue());
 
   26                         Integer longitude = Integer.valueOf(args[1].stringValue());
 
   27                         Integer latitude = Integer.valueOf(args[2].stringValue());
 
   28                         Geometry result = 
attribute(geom,longitude,latitude);
 
   29                         return valueFactory.createLiteral(((VectorLiteral) l).unparse(result),((Literal)args[0]).getDatatype());
 
abstract Geometry attribute(GridCoverage geom, Integer longitude, Integer latitude)