17         if (args.length != 2) {
 
   18                 throw new ValueExprEvaluationException(getURI() + 
" requires exactly 1 arguments, got " + args.length);
 
   20         LiteralType l=LiteralRegistry.getLiteral(((Literal)args[0]).getDatatype().toString());
 
   21         if(l instanceof RasterLiteral) {
 
   22                 GridCoverage geom=((RasterLiteral)l).read(args[0].stringValue());
 
   23                 Integer parameter = Integer.valueOf(args[1].stringValue());
 
   24                 Boolean result = 
attribute(geom,parameter);
 
   25                 return valueFactory.createLiteral(result);
 
abstract Boolean attribute(GridCoverage geom, Integer param)