diff --git a/src/main/java/eu/omp/irap/vespa/epntapclient/view/RequestView.java b/src/main/java/eu/omp/irap/vespa/epntapclient/view/RequestView.java
index 8d26f1a..0913d1c 100644
--- a/src/main/java/eu/omp/irap/vespa/epntapclient/view/RequestView.java
+++ b/src/main/java/eu/omp/irap/vespa/epntapclient/view/RequestView.java
@@ -18,24 +18,27 @@ package eu.omp.irap.vespa.epntapclient.view;
 
 import java.awt.BorderLayout;
 import java.awt.Dimension;
-import java.awt.GridLayout;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
+import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import javax.swing.BorderFactory;
 import javax.swing.BoxLayout;
 import javax.swing.JButton;
-import javax.swing.JLabel;
 import javax.swing.JPanel;
 import javax.swing.JTextArea;
-import javax.swing.JTextField;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import eu.omp.irap.vespa.epntapclient.utils.Queries;
+import eu.omp.irap.vespa.epntapclient.view.ParamField.DataProductTypeField;
+import eu.omp.irap.vespa.epntapclient.view.ParamField.DateRangeField;
+import eu.omp.irap.vespa.epntapclient.view.ParamField.FloatRangeField;
+import eu.omp.irap.vespa.epntapclient.view.ParamField.TargetNameField;
 import eu.omp.irap.vespa.epntapclient.votable.controller.VOTableException;
 
 /**
@@ -56,18 +59,17 @@ public class RequestView extends JPanel implements ActionListener {
 	private JTextArea queryArea;
 
 	// TODO: Use one map for paramFields, paramValues, paramTypes.
+
 	/**
 	 * The parameters fields for the request.
 	 */
-	private Map<String, JTextField> paramFields;
+	private List<ParamField> paramFields;
 
 	/**
 	 * The parameters fields for the request.
 	 */
 	private Map<String, Object> paramValues;
 
-	private Map<String, Class> paramTypes;
-
 	/** The height of the buttons panel. */
 	private static final int BUTTON_PANEL_HEIGHT = 15;
 
@@ -81,15 +83,6 @@ public class RequestView extends JPanel implements ActionListener {
 		setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
 
 		// TODO: Get max row number from the GUI
-		// TODO: auto-building range field by checking *_min / *_max attribute names
-
-		paramTypes = new HashMap<>();
-		paramTypes.put("target_name", String.class);
-		paramTypes.put("dataproduct_type", String.class);
-		paramTypes.put("minTime", Float.class);
-		paramTypes.put("maxTime", Float.class);
-		paramTypes.put("spectral_range_min", Float.class);
-		paramTypes.put("spectral_range_max", Float.class);
 
 		paramValues = new HashMap<>();
 
@@ -102,26 +95,21 @@ public class RequestView extends JPanel implements ActionListener {
 	 * @return A JPanel containing graphical elements for the service parameters.
 	 */
 	private JPanel buildParamPanel() {
-		paramFields = new HashMap();
-
-		// TODO: Find a way to set numerical value to "" by default.
 		// TODO: new GUI field column to allow the user to select the comparison operator:
 		// - if the field is a String: listbox with 'xx', '%xx', 'xx%', and '%xx%'.
 		// - if the field is a numeric value: listbox with <, <=, =, =>, >.
-		for (Map.Entry<String, Class> paramType : paramTypes.entrySet()) {
-			paramFields.put(paramType.getKey(),
-					new ParamField(this, paramType.getKey(), paramType.getValue()));
-		}
-
-		JPanel paramPanel = new JPanel(new GridLayout(0, 2));
+		paramFields = new ArrayList();
+		paramFields.add(new TargetNameField(this, "target_name"));
+		paramFields.add(new DateRangeField(this, "time_"));
+		paramFields.add(new FloatRangeField(this, "spectral_range_"));
+		paramFields.add(new DataProductTypeField(this, "dataproduct_type"));
+
+		JPanel paramPanel = new JPanel();
+		paramPanel.setLayout(new BoxLayout(paramPanel, BoxLayout.Y_AXIS));
 		paramPanel.setBorder(BorderFactory.createTitledBorder("Query parameters"));
 
-		for (Map.Entry<String, JTextField> e : paramFields.entrySet()) {
-			JLabel label = new JLabel(e.getKey());
-			paramPanel.add(label);
-
-			// TODO: Add tooltip text based on rr.table_column.column_description
-			paramPanel.add(e.getValue());
+		for (ParamField field : paramFields) {
+			paramPanel.add(field);
 		}
 
 		return paramPanel;
@@ -145,6 +133,7 @@ public class RequestView extends JPanel implements ActionListener {
 	public void updateParam(String paramName, Object value) {
 		logger.info("uploading " + paramName + ": " + value);
 		paramValues.put(paramName, value);
+		updateQueryArea();
 	}
 
 	/**
--
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