--- a/src/RelpipeChartMainWindow.cpp	Sun Sep 30 18:34:34 2018 +0200
+++ b/src/RelpipeChartMainWindow.cpp	Sun Sep 30 20:54:35 2018 +0200
@@ -23,7 +23,7 @@
 RelpipeChartMainWindow::~RelpipeChartMainWindow() {
 }
 
-void RelpipeChartMainWindow::startRelation(string_t name, std::vector<AttributeMetadata> attributes) {
+void RelpipeChartMainWindow::startRelation(const string_t name, std::vector<AttributeMetadata> attributes) {
 	setStatusMessage(L"Reading relation: " + name);
 	attributeCounter = 0;
 	QSplitter* splitter = new QSplitter(Qt::Orientation::Vertical, tabs);
@@ -43,7 +43,7 @@
 	tabs->setTabIcon(index, QIcon::fromTheme("application-vnd.oasis.opendocument.spreadsheet"));
 }
 
-void RelpipeChartMainWindow::attribute(const string_t& value) {
+void RelpipeChartMainWindow::attribute(const string_t value) {
 	// TODO: draw chart
 	integer_t column = attributeCounter % currentTable->columnCount();
 	integer_t row = attributeCounter / currentTable->columnCount();