diff --git a/doctrine-mapping.xsd b/doctrine-mapping.xsd
index 97d15379b..25976c428 100644
--- a/doctrine-mapping.xsd
+++ b/doctrine-mapping.xsd
@@ -57,12 +57,21 @@
   </xs:complexType>
   
   <xs:simpleType name="inheritance-type">
-    <xs:restriction base="xs:string">
-      <xs:enumeration value="single-table"/>
-      <xs:enumeration value="joined"/>
-      <xs:enumeration value="table-per-class"/>
+    <xs:restriction base="xs:token">
+      <xs:enumeration value="SINGLE_TABLE"/>
+      <xs:enumeration value="JOINED"/>
+      <xs:enumeration value="TABLE_PER_CLASS"/>
     </xs:restriction>
   </xs:simpleType>
+  
+  <xs:simpleType name="generator-strategy"> 
+    <xs:restriction base="xs:token"> 
+      <xs:enumeration value="TABLE"/> 
+      <xs:enumeration value="SEQUENCE"/> 
+      <xs:enumeration value="IDENTITY"/> 
+      <xs:enumeration value="AUTO"/> 
+    </xs:restriction> 
+  </xs:simpleType> 
 
   <xs:complexType name="field">
     <xs:attribute name="name" type="xs:NMTOKEN" use="required" />
@@ -72,7 +81,7 @@
   </xs:complexType>
 
   <xs:complexType name="generator">
-    <xs:attribute name="strategy" type="xs:NMTOKEN" use="required" />
+    <xs:attribute name="strategy" type="orm:generator-strategy" use="required" />
   </xs:complexType>
 
   <xs:complexType name="id">
diff --git a/lib/Doctrine/ORM/Mapping/ClassMetadata.php b/lib/Doctrine/ORM/Mapping/ClassMetadata.php
index 1c40bdb13..d56af872c 100644
--- a/lib/Doctrine/ORM/Mapping/ClassMetadata.php
+++ b/lib/Doctrine/ORM/Mapping/ClassMetadata.php
@@ -46,52 +46,52 @@ final class ClassMetadata
      * NONE means the class does not participate in an inheritance hierarchy
      * and therefore does not need an inheritance mapping type.
      */
-    const INHERITANCE_TYPE_NONE = 'none';
+    const INHERITANCE_TYPE_NONE = 1;
     /**
      * JOINED means the class will be persisted according to the rules of
      * <tt>Class Table Inheritance</tt>.
      */
-    const INHERITANCE_TYPE_JOINED = 'joined';
+    const INHERITANCE_TYPE_JOINED = 2;
     /**
      * SINGLE_TABLE means the class will be persisted according to the rules of
      * <tt>Single Table Inheritance</tt>.
      */
-    const INHERITANCE_TYPE_SINGLE_TABLE = 'singleTable';
+    const INHERITANCE_TYPE_SINGLE_TABLE = 3;
     /**
      * TABLE_PER_CLASS means the class will be persisted according to the rules
      * of <tt>Concrete Table Inheritance</tt>.
      */
-    const INHERITANCE_TYPE_TABLE_PER_CLASS = 'tablePerClass';
+    const INHERITANCE_TYPE_TABLE_PER_CLASS = 4;
     
     /* The Id generator types. */
     /**
      * AUTO means the generator type will depend on what the used platform prefers.
      * Offers full portability.
      */
-    const GENERATOR_TYPE_AUTO = 'auto';
+    const GENERATOR_TYPE_AUTO = 1;
     /**
      * SEQUENCE means a separate sequence object will be used. Platforms that do
      * not have native sequence support may emulate it. Full portability is currently
      * not guaranteed.
      */
-    const GENERATOR_TYPE_SEQUENCE = 'sequence';
+    const GENERATOR_TYPE_SEQUENCE = 2;
     /**
      * TABLE means a separate table is used for id generation.
      * Offers full portability.
      */
-    const GENERATOR_TYPE_TABLE = 'table';
+    const GENERATOR_TYPE_TABLE = 3;
     /**
      * IDENTITY means an identity column is used for id generation. The database
      * will fill in the id column on insertion. Platforms that do not support
      * native identity columns may emulate them. Full portability is currently
      * not guaranteed.
      */
-    const GENERATOR_TYPE_IDENTITY = 'identity';
+    const GENERATOR_TYPE_IDENTITY = 4;
     /**
      * NONE means the class does not have a generated id. That means the class
      * must have a natural id.
      */
-    const GENERATOR_TYPE_NONE = 'none';
+    const GENERATOR_TYPE_NONE = 5;
     /**
      * DEFERRED_IMPLICIT means that changes of entities are calculated at commit-time
      * by doing a property-by-property comparison with the original data. This will
@@ -1749,6 +1749,7 @@ final class ClassMetadata
      * Creates a string representation of this instance.
      *
      * @return string The string representation of this instance.
+     * @todo Construct meaningful string representation.
      */
     public function __toString()
     {
diff --git a/lib/Doctrine/ORM/Mapping/Driver/AnnotationDriver.php b/lib/Doctrine/ORM/Mapping/Driver/AnnotationDriver.php
index 82f2f0609..f183a91ba 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/AnnotationDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/AnnotationDriver.php
@@ -63,7 +63,7 @@ class AnnotationDriver implements Driver
 
         // Evaluate InheritanceType annotation
         if ($inheritanceTypeAnnot = $annotClass->getAnnotation('InheritanceType')) {
-            $metadata->setInheritanceType($inheritanceTypeAnnot->value);
+            $metadata->setInheritanceType(constant('\Doctrine\ORM\Mapping\ClassMetadata::INHERITANCE_TYPE_' . $inheritanceTypeAnnot->value));
         }
 
         // Evaluate DiscriminatorColumn annotation
@@ -130,7 +130,14 @@ class AnnotationDriver implements Driver
                     $mapping['id'] = true;
                 }
                 if ($generatedValueAnnot = $property->getAnnotation('GeneratedValue')) {
-                    $metadata->setIdGeneratorType($generatedValueAnnot->strategy);
+                    if ($generatedValueAnnot->strategy == 'auto') {
+                        try {
+                            throw new \Exception();
+                        } catch (\Exception $e) {
+                            var_dump($e->getTraceAsString());
+                        }
+                    }
+                    $metadata->setIdGeneratorType(constant('Doctrine\ORM\Mapping\ClassMetadata::GENERATOR_TYPE_' . $generatedValueAnnot->strategy));
                 }
                 $metadata->mapField($mapping);
 
diff --git a/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php b/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
index 8098f1c7f..257eff2eb 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/XmlDriver.php
@@ -86,7 +86,8 @@ class XmlDriver extends AbstractFileDriver
                 $metadata->mapField($mapping);
 
                 if (isset($idElement->generator)) {
-                    $metadata->setIdGeneratorType((string)$idElement->generator['strategy']);
+                    $metadata->setIdGeneratorType(constant('Doctrine\ORM\Mapping\ClassMetadata::GENERATOR_TYPE_'
+                            . (string)$idElement->generator['strategy']));
                 }
             }
 
diff --git a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
index 77bb3259f..01e882bf9 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/YamlDriver.php
@@ -87,7 +87,8 @@ class YamlDriver extends AbstractFileDriver
                 $metadata->mapField($mapping);
 
                 if (isset($idElement['generator'])) {
-                    $metadata->setIdGeneratorType($idElement['generator']['strategy']);
+                    $metadata->setIdGeneratorType(constant('Doctrine\ORM\Mapping\ClassMetadata::GENERATOR_TYPE_'
+                            . $idElement['generator']['strategy']));
                 }
             }
 
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsAddress.php b/tests/Doctrine/Tests/Models/CMS/CmsAddress.php
index d5980cffc..181e28b22 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsAddress.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsAddress.php
@@ -14,7 +14,7 @@ class CmsAddress
     /**
      * @Column(type="integer")
      * @Id
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
 
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsArticle.php b/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
index 2ff8a66f9..719f4b3d9 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsArticle.php
@@ -11,7 +11,7 @@ class CmsArticle
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsComment.php b/tests/Doctrine/Tests/Models/CMS/CmsComment.php
index 8e327a9a8..c1991474f 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsComment.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsComment.php
@@ -11,7 +11,7 @@ class CmsComment
     /**
      * @Column(type="integer")
      * @Id
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsEmployee.php b/tests/Doctrine/Tests/Models/CMS/CmsEmployee.php
index 8ecb26420..9acdbc6f4 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsEmployee.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsEmployee.php
@@ -14,7 +14,7 @@ class CmsEmployee
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     private $id;
 
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsGroup.php b/tests/Doctrine/Tests/Models/CMS/CmsGroup.php
index 2a4908927..3bdfcba1f 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsGroup.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsGroup.php
@@ -18,7 +18,7 @@ class CmsGroup
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/CMS/CmsUser.php b/tests/Doctrine/Tests/Models/CMS/CmsUser.php
index d8760cac0..50ab5daee 100644
--- a/tests/Doctrine/Tests/Models/CMS/CmsUser.php
+++ b/tests/Doctrine/Tests/Models/CMS/CmsUser.php
@@ -10,7 +10,7 @@ class CmsUser
 {
     /**
      * @Id @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/Company/CompanyPerson.php b/tests/Doctrine/Tests/Models/Company/CompanyPerson.php
index 03180d8ca..9444352ad 100644
--- a/tests/Doctrine/Tests/Models/Company/CompanyPerson.php
+++ b/tests/Doctrine/Tests/Models/Company/CompanyPerson.php
@@ -9,7 +9,7 @@ namespace Doctrine\Tests\Models\Company;
  * @Entity
  * @Table(name="company_persons")
  * @DiscriminatorValue("person")
- * @InheritanceType("joined")
+ * @InheritanceType("JOINED")
  * @DiscriminatorColumn(name="discr", type="string")
  * @SubClasses({"Doctrine\Tests\Models\Company\CompanyEmployee",
         "Doctrine\Tests\Models\Company\CompanyManager"})
@@ -19,7 +19,7 @@ class CompanyPerson
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     private $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/Forum/ForumAvatar.php b/tests/Doctrine/Tests/Models/Forum/ForumAvatar.php
index 691ac022d..ce4e3c30d 100644
--- a/tests/Doctrine/Tests/Models/Forum/ForumAvatar.php
+++ b/tests/Doctrine/Tests/Models/Forum/ForumAvatar.php
@@ -11,7 +11,7 @@ class ForumAvatar
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
 }
diff --git a/tests/Doctrine/Tests/Models/Forum/ForumEntry.php b/tests/Doctrine/Tests/Models/Forum/ForumEntry.php
index 3a114115e..736c2adb6 100644
--- a/tests/Doctrine/Tests/Models/Forum/ForumEntry.php
+++ b/tests/Doctrine/Tests/Models/Forum/ForumEntry.php
@@ -11,7 +11,7 @@ class ForumEntry
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/Models/Forum/ForumUser.php b/tests/Doctrine/Tests/Models/Forum/ForumUser.php
index ad2977c0e..6b15890ec 100644
--- a/tests/Doctrine/Tests/Models/Forum/ForumUser.php
+++ b/tests/Doctrine/Tests/Models/Forum/ForumUser.php
@@ -11,7 +11,7 @@ class ForumUser
     /**
      * @Column(type="integer")
      * @Id
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     public $id;
     /**
diff --git a/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php b/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
index 0b5016cb1..9ee31b085 100644
--- a/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
+++ b/tests/Doctrine/Tests/ORM/Functional/SingleTableInheritanceTest.php
@@ -97,7 +97,7 @@ class SingleTableInheritanceTest extends \Doctrine\Tests\OrmFunctionalTestCase
 
 /**
  * @Entity
- * @InheritanceType("singleTable")
+ * @InheritanceType("SINGLE_TABLE")
  * @DiscriminatorColumn(name="discr", type="string")
  * @SubClasses({"Doctrine\Tests\ORM\Functional\ChildEntity"})
  * @DiscriminatorValue("parent")
@@ -106,7 +106,7 @@ class ParentEntity {
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     private $id;
 
@@ -168,7 +168,7 @@ class RelatedEntity {
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     private $id;
     /**
diff --git a/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php b/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
index cbebad0a3..5f50d80fc 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
+++ b/tests/Doctrine/Tests/ORM/Mapping/ClassMetadataFactoryTest.php
@@ -27,7 +27,7 @@ class ClassMetadataFactoryTest extends \Doctrine\Tests\OrmTestCase
         // and a mapped association
         $cm1->mapOneToOne(array('fieldName' => 'other', 'targetEntity' => 'Other', 'mappedBy' => 'this'));
         // and an id generator type
-        $cm1->setIdGeneratorType('auto');
+        $cm1->setIdGeneratorType(ClassMetadata::GENERATOR_TYPE_AUTO);
 
         // SUT
         $cmf = new ClassMetadataFactoryTestSubject($mockDriver, $mockPlatform);
@@ -35,17 +35,17 @@ class ClassMetadataFactoryTest extends \Doctrine\Tests\OrmTestCase
 
         // Prechecks
         $this->assertEquals(array(), $cm1->parentClasses);
-        $this->assertEquals('none', $cm1->inheritanceType);
+        $this->assertEquals(ClassMetadata::INHERITANCE_TYPE_NONE, $cm1->inheritanceType);
         $this->assertTrue($cm1->hasField('name'));
         $this->assertEquals(1, count($cm1->associationMappings));
-        $this->assertEquals('auto', $cm1->generatorType);
+        $this->assertEquals(ClassMetadata::GENERATOR_TYPE_AUTO, $cm1->generatorType);
 
         // Go
         $cm1 = $cmf->getMetadataFor('Doctrine\Tests\ORM\Mapping\TestEntity1');
 
         $this->assertEquals(array(), $cm1->parentClasses);
         $this->assertTrue($cm1->hasField('name'));
-        $this->assertEquals('sequence', $cm1->generatorType);
+        $this->assertEquals(ClassMetadata::GENERATOR_TYPE_SEQUENCE, $cm1->generatorType);
     }
 }
 
diff --git a/tests/Doctrine/Tests/ORM/Mapping/xml/XmlMappingTest.User.dcm.xml b/tests/Doctrine/Tests/ORM/Mapping/xml/XmlMappingTest.User.dcm.xml
index 57abf84ea..0945821a5 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/xml/XmlMappingTest.User.dcm.xml
+++ b/tests/Doctrine/Tests/ORM/Mapping/xml/XmlMappingTest.User.dcm.xml
@@ -8,7 +8,7 @@
     <entity name="XmlMappingTest\User" table="cms_users">
     
         <id name="id" type="integer" column="id">
-            <generator strategy="auto"/>
+            <generator strategy="AUTO"/>
         </id>
         
         <field name="name" column="name" type="string" length="50"/>
@@ -34,7 +34,6 @@
             </join-table>
         </many-to-many>
         
-        
     </entity>
 
 </doctrine-mapping>
\ No newline at end of file
diff --git a/tests/Doctrine/Tests/ORM/Mapping/yaml/YamlMappingTest.User.dcm.yml b/tests/Doctrine/Tests/ORM/Mapping/yaml/YamlMappingTest.User.dcm.yml
index d6c63d417..6de3a2f92 100644
--- a/tests/Doctrine/Tests/ORM/Mapping/yaml/YamlMappingTest.User.dcm.yml
+++ b/tests/Doctrine/Tests/ORM/Mapping/yaml/YamlMappingTest.User.dcm.yml
@@ -5,7 +5,7 @@ YamlMappingTest\User:
     id:
       type: integer
       generator:
-        strategy: auto
+        strategy: AUTO
   fields:
     name:
       type: string
diff --git a/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php b/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
index 89a128922..dff775bf3 100644
--- a/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
+++ b/tests/Doctrine/Tests/ORM/UnitOfWorkTest.php
@@ -193,7 +193,7 @@ class NotifyChangedEntity implements \Doctrine\Common\NotifyPropertyChanged
     /**
      * @Id
      * @Column(type="integer")
-     * @GeneratedValue(strategy="auto")
+     * @GeneratedValue(strategy="AUTO")
      */
     private $id;
     /**