diff -r 157bb1d5e08a -r 15ee963675af src/CSVCommand.cpp
--- a/src/CSVCommand.cpp	Wed Sep 23 11:26:33 2020 +0200
+++ b/src/CSVCommand.cpp	Wed Sep 23 16:58:48 2020 +0200
@@ -87,7 +87,7 @@
 	return false;
 }
 
-void CSVCommand::process(std::istream& input, const vector<relpipe::writer::string_t>& args, std::shared_ptr<writer::RelationalWriter> writer) {
+void CSVCommand::process(std::istream& input, std::shared_ptr<writer::RelationalWriter> writer, Configuration& configuration) {
 	wstring_convert < codecvt_utf8<wchar_t>> convertor; // UTF-8 is required for CSV
 	vector<AttributeMetadata> metadata;
 	bool headerDone = false;
@@ -105,30 +105,28 @@
 			metadata.push_back(am);
 			if (lastInRecord) {
 
-				/*
-				 * Usage (simple syntax):
-				 * relpipe-in-csv → default relation name, attribute names on the first line, all types are string
-				 * relpipe-in-csv my_relation → custom relation name
-				 * relpipe-in-csv my_relation a b c → custom relation name, custom attribute names (a,b,c), first line contains data
-				 * relpipe-in-csv my_relation a integer b string c boolean → custom relation name, custom attribute names (a,b,c), custom types (integer,string,boolean), first line contains data
-				 */
+				// TODO: allow types on CLI and names from CSV?
+				// TODO: allow types on the second line of the CSV?
+				// TODO: allow regex pattern+replacement for extracting name and type from the first line of the CSV?
+				// TODO: allow attribute filtering, subset, like relpipe-tr-cur?
+				// TODO: allow skipping lines, like tail -n +2 ?
+				
+				vector<string_t> firstLine;
 
-				vector<string_t> firstLine;
-				if (args.size() == (1 + metadata.size())) {
+				if (metadata.size() == configuration.attributes.size()) {
 					for (int i = 0; i < metadata.size(); i++) {
 						firstLine.push_back(metadata[i].attributeName);
-						metadata[i].attributeName = args[1 + i];
+						metadata[i].attributeName = configuration.attributes[i].name;
+						metadata[i].typeId = configuration.attributes[i].type;
 					}
-				} else if (args.size() == (1 + 2 * metadata.size())) {
-					for (int i = 0; i < metadata.size(); i++) {
-						firstLine.push_back(metadata[i].attributeName);
-						metadata[i].attributeName = args[1 + i * 2];
-						metadata[i].typeId = writer->toTypeId(args[1 + i * 2 + 1]);
-					}
+				} else if (configuration.attributes.size() == 0) {
+					// first line contains attribute names and type is always string
+				} else {
+					throw RelpipeWriterException(L"Declared attribute count (" + std::to_wstring(configuration.attributes.size()) + L") does not match with number of columns of the first line (" + std::to_wstring(metadata.size()) + L")");
 				}
 
 				headerDone = true;
-				writer->startRelation(args.size() > 0 ? args[0] : L"csv", metadata, true);
+				writer->startRelation(configuration.relation, metadata, true);
 				if (firstLine.size()) {
 					for (string_t value : firstLine) writer->writeAttribute(value);
 				}