diff --git a/com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Properties_calculateTagNumberOf_Test.java b/com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Fields_calculateTagNumberOf_Test.java
similarity index 83%
rename from com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Properties_calculateTagNumberOf_Test.java
rename to com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Fields_calculateTagNumberOf_Test.java
index a62b373..032d125 100644
--- a/com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Properties_calculateTagNumberOf_Test.java
+++ b/com.google.eclipse.protobuf.ui.test/src/com/google/eclipse/protobuf/ui/util/Fields_calculateTagNumberOf_Test.java
@@ -19,18 +19,18 @@
 import com.google.eclipse.protobuf.protobuf.Protobuf;
 
 /**
- * Tests for <code>{@link Properties#calculateTagNumberOf(Property)}</code>.
+ * Tests for <code>{@link Fields#calculateTagNumberOf(Property)}</code>.
  *
  * @author alruiz@google.com (Alex Ruiz)
  */
-public class Properties_calculateTagNumberOf_Test {
+public class Fields_calculateTagNumberOf_Test {
 
   @Rule public XtextRule xtext = new XtextRule();
 
-  private Properties properties;
+  private Fields fields;
 
   @Before public void setUp() {
-    properties = xtext.getInstanceOf(Properties.class);
+    fields = xtext.getInstanceOf(Fields.class);
   }
 
   @Test public void should_return_one_for_first_and_only_property() {
@@ -40,7 +40,7 @@
          .append("}                          ");
     Protobuf root = xtext.parse(proto);
     Property name = findProperty("name", root);
-    int index = properties.calculateTagNumberOf(name);
+    int index = fields.calculateTagNumberOf(name);
     assertThat(index, equalTo(1));
   }
 
@@ -52,7 +52,7 @@
          .append("}                          ");
     Protobuf root = xtext.parse(proto);
     Property id = findProperty("id", root);
-    int index = properties.calculateTagNumberOf(id);
+    int index = fields.calculateTagNumberOf(id);
     assertThat(index, equalTo(7));
   }
 }
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/builder/ProtocMarkerFactory.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/builder/ProtocMarkerFactory.java
index a1eb6c9..1188d40 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/builder/ProtocMarkerFactory.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/builder/ProtocMarkerFactory.java
@@ -33,7 +33,7 @@
     file.deleteMarkers(PROTOC, true, DEPTH_INFINITE);
     markers = file.findMarkers(FAST_VALIDATION, true, DEPTH_INFINITE);
   }
-  
+
   void createErrorIfNecessary(String message, int lineNumber) throws CoreException {
     if (containsMarker(message, lineNumber)) return;
     IMarker marker = file.createMarker(PROTOC);
@@ -41,11 +41,13 @@
     marker.setAttribute(MESSAGE, message);
     marker.setAttribute(LINE_NUMBER, lineNumber);
   }
-  
+
   private boolean containsMarker(String description, int lineNumber) throws CoreException {
-    for (IMarker marker : markers)
-      if (marker.getAttribute(MESSAGE).equals(description) && marker.getAttribute(LINE_NUMBER).equals(lineNumber))
+    for (IMarker marker : markers) {
+      String markerMessage = (String) marker.getAttribute(MESSAGE);
+      if (markerMessage.equalsIgnoreCase(description) && marker.getAttribute(LINE_NUMBER).equals(lineNumber))
         return true;
+    }
     return false;
   }
 }
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/commands/SmartSemicolonHandler.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/commands/SmartSemicolonHandler.java
index 3216b10..6f52c7e 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/commands/SmartSemicolonHandler.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/commands/SmartSemicolonHandler.java
@@ -20,8 +20,10 @@
 import org.eclipse.xtext.ui.editor.contentassist.antlr.ParserBasedContentAssistContextFactory;
 import org.eclipse.xtext.util.concurrent.IUnitOfWork;
 
-import com.google.eclipse.protobuf.protobuf.*;
-import com.google.eclipse.protobuf.ui.util.*;
+import com.google.eclipse.protobuf.protobuf.Literal;
+import com.google.eclipse.protobuf.protobuf.Property;
+import com.google.eclipse.protobuf.ui.util.Fields;
+import com.google.eclipse.protobuf.ui.util.Literals;
 import com.google.inject.Inject;
 
 /**
@@ -39,8 +41,8 @@
       Pattern.compile("[\\s]+(.*)[\\s]+(.*)[\\s]+(.*)[\\s]+=[\\s]+[\\d]+(.*)");
 
   @Inject private ParserBasedContentAssistContextFactory contextFactory;
+  @Inject private Fields fields;
   @Inject private Literals literals;
-  @Inject private Properties properties;
 
   private final String semicolon = SEMICOLON.toString();
 
@@ -94,7 +96,7 @@
   private String contentToInsert(String line, Property property) {
     boolean hasIndexAlready = PROPERTY_WITH_INDEX.matcher(line).matches();
     if (hasIndexAlready) return semicolon;
-    int index = properties.calculateTagNumberOf(property);
+    int index = fields.calculateTagNumberOf(property);
     return defaultIndexAndSemicolonToInsert(line, index);
   }
 
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/contentassist/ProtobufProposalProvider.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/contentassist/ProtobufProposalProvider.java
index 072435b..c6342f0 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/contentassist/ProtobufProposalProvider.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/contentassist/ProtobufProposalProvider.java
@@ -50,7 +50,9 @@
   @Inject private ProtobufElementFinder finder;
   @Inject private DescriptorProvider descriptorProvider;
   @Inject private PluginImageHelper imageHelper;
-  @Inject private Images imageRegistry;
+
+  @Inject private Fields fields;
+  @Inject private Images images;
   @Inject private Literals literals;
   @Inject private Properties properties;
   @Inject private Strings strings;
@@ -68,7 +70,7 @@
   @Override public void complete_Syntax(EObject model, RuleCall ruleCall, ContentAssistContext context,
       ICompletionProposalAcceptor acceptor) {
     String proposal = SYNTAX + SPACE + EQUAL_PROTO2_IN_QUOTES;
-    proposeAndAccept(proposal, imageHelper.getImage(imageRegistry.imageFor(Syntax.class)), context, acceptor);
+    proposeAndAccept(proposal, imageHelper.getImage(images.imageFor(Syntax.class)), context, acceptor);
   }
 
   @Override public void completeOption_Name(EObject model, Assignment assignment, ContentAssistContext context,
@@ -285,7 +287,7 @@
 
   @Override public void completeProperty_Index(EObject model, Assignment assignment, ContentAssistContext context,
       ICompletionProposalAcceptor acceptor) {
-    int index = properties.calculateTagNumberOf((Property) model);
+    int index = fields.calculateTagNumberOf((Property) model);
     proposeIndex(index, context, acceptor);
   }
 
@@ -322,14 +324,14 @@
   }
 
   private Image defaultImage() {
-    return imageHelper.getImage(imageRegistry.defaultImage());
+    return imageHelper.getImage(images.defaultImage());
   }
-  
+
   @Override public void complete_FieldOption(EObject model, RuleCall ruleCall, ContentAssistContext context,
       ICompletionProposalAcceptor acceptor) {
     System.out.println("complete_FieldOption");
   }
-  
+
   @Override public void completeFieldOption_Name(EObject model, Assignment assignment, ContentAssistContext context,
       ICompletionProposalAcceptor acceptor) {
     Property property = extractPropertyFrom(context);
@@ -349,7 +351,7 @@
       acceptor.accept(proposal);
     }
   }
-  
+
   private List<String> existingFieldOptionNames(Property property) {
     List<FieldOption> options = property.getFieldOptions();
     if (options.isEmpty()) return emptyList();
@@ -361,7 +363,7 @@
   private boolean canBePacked(Property property) {
     return properties.isPrimitive(property) && REPEATED.equals(property.getModifier());
   }
-  
+
   @Override public void completeFieldOption_Value(EObject model, Assignment assignment, ContentAssistContext context,
       ICompletionProposalAcceptor acceptor) {
     FieldOption option = (FieldOption) model;
@@ -389,7 +391,7 @@
   }
 
   private void proposeAndAccept(Enum enumType, ContentAssistContext context, ICompletionProposalAcceptor acceptor) {
-    Image image = imageHelper.getImage(imageRegistry.imageFor(Literal.class));
+    Image image = imageHelper.getImage(images.imageFor(Literal.class));
     for (Literal literal : enumType.getLiterals())
       proposeAndAccept(literal.getName(), image, context, acceptor);
   }
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Fields.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Fields.java
new file mode 100644
index 0000000..a9e8d40
--- /dev/null
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Fields.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2011 Google Inc.
+ *
+ * All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse
+ * Public License v1.0 which accompanies this distribution, and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+package com.google.eclipse.protobuf.ui.util;
+
+import static java.lang.Math.max;
+
+import org.eclipse.emf.ecore.EObject;
+
+import com.google.eclipse.protobuf.protobuf.Field;
+import com.google.inject.Singleton;
+
+/**
+ * Utility methods re <code>{@link Field}</code>.
+ *
+ * @author alruiz@google.com (Alex Ruiz)
+ */
+@Singleton
+public class Fields {
+
+  /**
+   * Calculates the tag number value for the given field. The calculated tag number value is the maximum of all the
+   * tag number values of the given field's siblings, plus one. The minimum tag number value is 1.
+   * <p>
+   * For example, in the following message:
+   *
+   * <pre>
+   * message Person {
+   *   required string name = 1;
+   *   optional string email = 2;
+   *   optional PhoneNumber phone =
+   * </pre>
+   *
+   * The calculated tag number value for the field {@code PhoneNumber} will be 3.
+   * </p>
+   * @param p the given field.
+   * @return the calculated value for the tag number of the given field.
+   */
+  public int calculateTagNumberOf(Field f) {
+    int index = 0;
+    for (EObject o : f.eContainer().eContents()) {
+      if (o == f || !(o instanceof Field)) continue;
+      index = max(index, ((Field) o).getIndex());
+    }
+    return ++index;
+  }
+}
diff --git a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Properties.java b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Properties.java
index b9dd4f1..f9668cd 100644
--- a/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Properties.java
+++ b/com.google.eclipse.protobuf.ui/src/com/google/eclipse/protobuf/ui/util/Properties.java
@@ -9,10 +9,6 @@
 package com.google.eclipse.protobuf.ui.util;
 
 import static com.google.eclipse.protobuf.ui.grammar.CommonKeyword.*;
-import static java.lang.Math.max;
-import static org.eclipse.xtext.EcoreUtil2.getAllContentsOfType;
-
-import java.util.List;
 
 import com.google.eclipse.protobuf.protobuf.*;
 import com.google.eclipse.protobuf.ui.grammar.CommonKeyword;
@@ -76,32 +72,4 @@
     }
     return r.toString();
   }
-
-  /**
-   * Calculates the tag number value for the given property. The calculated tag number value is the maximum of all the
-   * tag number values of the given property's siblings, plus one. The minimum tag number value is 1.
-   * <p>
-   * For example, in the following message:
-   *
-   * <pre>
-   * message Person {
-   *   required string name = 1;
-   *   optional string email = 2;
-   *   optional PhoneNumber phone =
-   * </pre>
-   *
-   * The calculated tag number value for the property {@code PhoneNumber} will be 3.
-   * </p>
-   * @param p the given property.
-   * @return the calculated value for the tag number of the given property.
-   */
-  public int calculateTagNumberOf(Property p) {
-    int index = 0;
-    List<Property> allProperties = getAllContentsOfType(p.eContainer(), Property.class);
-    for (Property c : allProperties) {
-      if (c == p) continue;
-      index = max(index, c.getIndex());
-    }
-    return ++index;
-  }
 }
diff --git a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
index 9cc6fd4..9926ea1 100644
--- a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
+++ b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/Protobuf.xtext
@@ -47,7 +47,10 @@
   '}'(';')?;
 
 MessageElement:
-  Type | Property | Group | ExtendMessage | Option;
+  Type | Field | ExtendMessage | Option;
+
+Field:
+  Property | Group;
 
 Group:
   modifier=Modifier 'group' name=ID '=' index=INT 
diff --git a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/validation/ProtobufJavaValidator.java b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/validation/ProtobufJavaValidator.java
index eb49e53..baca753 100644
--- a/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/validation/ProtobufJavaValidator.java
+++ b/com.google.eclipse.protobuf/src/com/google/eclipse/protobuf/validation/ProtobufJavaValidator.java
@@ -15,7 +15,8 @@
 
 import org.eclipse.emf.common.util.URI;
 import org.eclipse.emf.ecore.EObject;
-import org.eclipse.xtext.naming.*;
+import org.eclipse.xtext.naming.IQualifiedNameProvider;
+import org.eclipse.xtext.naming.QualifiedName;
 import org.eclipse.xtext.validation.Check;
 
 import com.google.eclipse.protobuf.protobuf.*;
@@ -45,34 +46,34 @@
     error(msg, SYNTAX__NAME);
   }
 
-  @Check public void checkTagNumberIsUnique(Property property) {
-    if (isNameNull(property)) return; // we already show an error if name is null, no need to go further.
-    int index = property.getIndex();
-    EObject container = property.eContainer();
+  @Check public void checkTagNumberIsUnique(Field field) {
+    if (isNameNull(field)) return; // we already show an error if name is null, no need to go further.
+    int index = field.getIndex();
+    EObject container = field.eContainer();
     if (container instanceof Message) {
       Message message = (Message) container;
       for (MessageElement element : message.getElements()) {
-        if (!(element instanceof Property)) continue;
-        Property p = (Property) element;
-        if (p == property) break;
-        if (p.getIndex() != index) continue;
+        if (!(element instanceof Field)) continue;
+        Field other = (Field) element;
+        if (other == field) break;
+        if (other.getIndex() != index) continue;
         QualifiedName messageName = qualifiedNameProvider.getFullyQualifiedName(message);
-        String msg = format(fieldNumberAlreadyUsed, index, messageName.toString(), p.getName());
-        error(msg, PROPERTY__INDEX);
+        String msg = format(fieldNumberAlreadyUsed, index, messageName.toString(), other.getName());
+        error(msg, FIELD__INDEX);
         break;
       }
     }
   }
 
-  @Check public void checkTagNumberIsGreaterThanZero(Property property) {
-    if (isNameNull(property)) return; // we already show an error if name is null, no need to go further.
-    int index = property.getIndex();
+  @Check public void checkTagNumberIsGreaterThanZero(Field field) {
+    if (isNameNull(field)) return; // we already show an error if name is null, no need to go further.
+    int index = field.getIndex();
     if (index > 0) return;
     String msg = (index == 0) ? fieldNumbersMustBePositive : expectedFieldNumber;
-    error(msg, PROPERTY__INDEX);
+    error(msg, FIELD__INDEX);
   }
 
-  private boolean isNameNull(Property property) {
-    return property.getName() == null;
+  private boolean isNameNull(Field field) {
+    return field.getName() == null;
   }
 }