diff --git a/utest/test_frontend.py b/utest/test_frontend.py
index 609a262..9249273 100755
--- a/utest/test_frontend.py
+++ b/utest/test_frontend.py
@@ -81,26 +81,26 @@
         # Not testing the parser, just making sure the AST is what we expect
         expected_ast = [
             ['metadata', 'version', '1'],
-            ['enum', 'ofp_port_config', [
-                ['OFPPC_PORT_DOWN', 1],
-                ['OFPPC_NO_STP', 2],
-                ['OFPPC_NO_RECV', 4],
-                ['OFPPC_NO_RECV_STP', 8],
-                ['OFPPC_NO_FLOOD', 16],
-                ['OFPPC_NO_FWD', 32],
-                ['OFPPC_NO_PACKET_IN', 64]]],
+            ['enum', 'ofp_port_config', [], [
+                ['OFPPC_PORT_DOWN', [], 1],
+                ['OFPPC_NO_STP', [], 2],
+                ['OFPPC_NO_RECV', [], 4],
+                ['OFPPC_NO_RECV_STP', [], 8],
+                ['OFPPC_NO_FLOOD', [], 16],
+                ['OFPPC_NO_FWD', [], 32],
+                ['OFPPC_NO_PACKET_IN', [], 64]]],
             ['metadata', 'version', '2'],
-            ['struct', 'of_echo_reply', None, [
+            ['struct', 'of_echo_reply', [], None, [
                 ['data', 'uint8_t', 'version'],
                 ['type', 'uint8_t', 'type', 3],
                 ['data', 'uint16_t', 'length'],
                 ['data', 'uint32_t', 'xid'],
                 ['data', 'of_octets_t', 'data']]],
-            ['enum', 'ofp_queue_op_failed_code', [
-                ['OFPQOFC_BAD_PORT', 0],
-                ['OFPQOFC_BAD_QUEUE', 1],
-                ['OFPQOFC_EPERM', 2]]],
-            ['struct', 'of_packet_queue', None, [
+            ['enum', 'ofp_queue_op_failed_code', [], [
+                ['OFPQOFC_BAD_PORT', [], 0],
+                ['OFPQOFC_BAD_QUEUE', [], 1],
+                ['OFPQOFC_EPERM', [], 2]]],
+            ['struct', 'of_packet_queue', [], None, [
                 ['data', 'uint32_t', 'queue_id'],
                 ['data', 'uint16_t', 'len'],
                 ['pad', 2],
@@ -111,32 +111,32 @@
         ofinput = frontend.create_ofinput(ast)
         self.assertEquals(set([1, 2]), ofinput.wire_versions)
         expected_classes = [
-            OFClass('of_echo_reply', None, [
+            OFClass(name='of_echo_reply', superclass=None, members=[
                 OFDataMember('version', 'uint8_t'), # XXX
                 OFTypeMember('type', 'uint8_t', 3),
                 OFLengthMember('length', 'uint16_t'),
                 OFDataMember('xid', 'uint32_t'),
-                OFDataMember('data', 'of_octets_t')]),
-            OFClass('of_packet_queue', None, [
+                OFDataMember('data', 'of_octets_t')], virtual=False, params={}),
+            OFClass(name='of_packet_queue', superclass=None, members=[
                 OFDataMember('queue_id', 'uint32_t'),
                 OFLengthMember('len', 'uint16_t'),
                 OFPadMember(2),
-                OFDataMember('properties', 'list(of_queue_prop_t)')]),
+                OFDataMember('properties', 'list(of_queue_prop_t)')], virtual=False, params={}),
         ]
         self.assertEquals(expected_classes, ofinput.classes)
         expected_enums = [
-            OFEnum('ofp_port_config', [
-                ('OFPPC_PORT_DOWN', 1),
-                ('OFPPC_NO_STP', 2),
-                ('OFPPC_NO_RECV', 4),
-                ('OFPPC_NO_RECV_STP', 8),
-                ('OFPPC_NO_FLOOD', 16),
-                ('OFPPC_NO_FWD', 32),
-                ('OFPPC_NO_PACKET_IN', 64)]),
-            OFEnum('ofp_queue_op_failed_code', [
-                ('OFPQOFC_BAD_PORT', 0),
-                ('OFPQOFC_BAD_QUEUE', 1),
-                ('OFPQOFC_EPERM', 2)]),
+            OFEnum(name='ofp_port_config', entries=[
+                OFEnumEntry('OFPPC_PORT_DOWN', 1, {}),
+                OFEnumEntry('OFPPC_NO_STP', 2, {}),
+                OFEnumEntry('OFPPC_NO_RECV', 4, {}),
+                OFEnumEntry('OFPPC_NO_RECV_STP', 8, {}),
+                OFEnumEntry('OFPPC_NO_FLOOD', 16, {}),
+                OFEnumEntry('OFPPC_NO_FWD', 32, {}),
+                OFEnumEntry('OFPPC_NO_PACKET_IN', 64, {})], params={}),
+            OFEnum(name='ofp_queue_op_failed_code', entries=[
+                OFEnumEntry('OFPQOFC_BAD_PORT', 0, {}),
+                OFEnumEntry('OFPQOFC_BAD_QUEUE', 1, {}),
+                OFEnumEntry('OFPQOFC_EPERM', 2, {})], params={}),
         ]
         self.assertEquals(expected_enums, ofinput.enums)
 
@@ -145,7 +145,7 @@
 #version 1
 
 struct of_queue_prop {
-    uint16_t type;
+    uint16_t type == ?;
     uint16_t len;
     pad(4);
 };
@@ -163,12 +163,12 @@
         expected_ast = [
             ['metadata', 'version', '1'],
 
-            ['struct', 'of_queue_prop', None, [
-                ['data', 'uint16_t', 'type'],
+            ['struct', 'of_queue_prop', [], None, [
+                ['discriminator', 'uint16_t', 'type'],
                 ['data', 'uint16_t', 'len'],
                 ['pad', 4]]],
 
-            ['struct', 'of_queue_prop_min_rate', 'of_queue_prop', [
+            ['struct', 'of_queue_prop_min_rate', [], 'of_queue_prop', [
                 ['type', 'uint16_t', 'type', 1],
                 ['data', 'uint16_t', 'len'],
                 ['pad', 4],
@@ -179,16 +179,16 @@
 
         ofinput = frontend.create_ofinput(ast)
         expected_classes = [
-            OFClass('of_queue_prop', None, [
-                OFDataMember('type', 'uint16_t'),
+            OFClass(name='of_queue_prop', superclass=None, members=[
+                OFDiscriminatorMember('type', 'uint16_t'),
                 OFLengthMember('len', 'uint16_t'),
-                OFPadMember(4)]),
-            OFClass('of_queue_prop_min_rate', 'of_queue_prop', [
+                OFPadMember(4)], virtual=True, params={}),
+            OFClass(name='of_queue_prop_min_rate', superclass='of_queue_prop', members= [
                 OFTypeMember('type', 'uint16_t', 1),
                 OFLengthMember('len', 'uint16_t'),
                 OFPadMember(4),
                 OFDataMember('rate', 'uint16_t'),
-                OFPadMember(6)]),
+                OFPadMember(6)], virtual=False, params= {}),
         ]
         self.assertEquals(expected_classes, ofinput.classes)
 
diff --git a/utest/test_parser.py b/utest/test_parser.py
index c24665c..8199096 100755
--- a/utest/test_parser.py
+++ b/utest/test_parser.py
@@ -42,7 +42,7 @@
 struct foo { };
 """
         ast = parser.parse(src)
-        self.assertEquals(ast, [['struct', 'foo', None, []]])
+        self.assertEquals(ast, [['struct', 'foo', [], None, []]])
 
     def test_one_field(self):
         src = """\
@@ -52,7 +52,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['data', 'uint32_t', 'bar']]]])
+            [['struct', 'foo', [], None, [['data', 'uint32_t', 'bar']]]])
 
     def test_multiple_fields(self):
         src = """\
@@ -64,7 +64,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None,
+            [['struct', 'foo', [], None,
                 [['data', 'uint32_t', 'bar'],
                  ['data', 'uint8_t', 'baz'],
                  ['data', 'uint64_t', 'abc']]]])
@@ -77,7 +77,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['data', 'uint32_t[4]', 'bar']]]])
+            [['struct', 'foo', [], None, [['data', 'uint32_t[4]', 'bar']]]])
 
     def test_list_type(self):
         src = """\
@@ -87,7 +87,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['data', 'list(of_action_t)', 'bar']]]])
+            [['struct', 'foo', [], None, [['data', 'list(of_action_t)', 'bar']]]])
 
     def test_pad_member(self):
         src = """\
@@ -97,7 +97,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['pad', 1]]]])
+            [['struct', 'foo', [], None, [['pad', 1]]]])
 
     def test_type_member(self):
         src = """\
@@ -107,7 +107,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['type', 'uint16_t', 'foo', 0x10]]]])
+            [['struct', 'foo', [], None, [['type', 'uint16_t', 'foo', 0x10]]]])
 
     def test_inheritance(self):
         src = """\
@@ -117,7 +117,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', 'bar', [['type', 'uint16_t', 'foo', 0x10]]]])
+            [['struct', 'foo', [], 'bar', [['type', 'uint16_t', 'foo', 0x10]]]])
 
 class EnumTests(unittest.TestCase):
     def test_empty(self):
@@ -126,7 +126,7 @@
 };
 """
         ast = parser.parse(src)
-        self.assertEquals(ast, [['enum', 'foo', []]])
+        self.assertEquals(ast, [['enum', 'foo', [], []]])
 
     def test_one(self):
         src = """\
@@ -135,7 +135,7 @@
 };
 """
         ast = parser.parse(src)
-        self.assertEquals(ast, [['enum', 'foo', [['BAR', 1]]]])
+        self.assertEquals(ast, [['enum', 'foo', [], [['BAR', [], 1]]]])
 
     def test_multiple(self):
         src = """\
@@ -146,7 +146,7 @@
 };
 """
         ast = parser.parse(src)
-        self.assertEquals(ast, [['enum', 'foo', [['OFP_A', 1], ['OFP_B', 2], ['OFP_C', 3]]]])
+        self.assertEquals(ast, [['enum', 'foo', [], [['OFP_A', [], 1], ['OFP_B', [], 2], ['OFP_C', [], 3]]]])
 
     def test_trailing_comma(self):
         src = """\
@@ -157,7 +157,7 @@
 };
 """
         ast = parser.parse(src)
-        self.assertEquals(ast, [['enum', 'foo', [['OFP_A', 1], ['OFP_B', 2], ['OFP_C', 3]]]])
+        self.assertEquals(ast, [['enum', 'foo', [], [['OFP_A', [], 1], ['OFP_B', [], 2], ['OFP_C', [], 3]]]])
 
 class TestMetadata(unittest.TestCase):
     def test_version(self):
@@ -175,7 +175,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, []], ['struct', 'bar', None, []]])
+            [['struct', 'foo', [], None, []], ['struct', 'bar', [], None, []]])
 
     def test_comments(self):
         src = """\
@@ -189,7 +189,7 @@
 """
         ast = parser.parse(src)
         self.assertEquals(ast,
-            [['struct', 'foo', None, [['data', 'uint32_t', 'a']]]])
+            [['struct', 'foo', [], None, [['data', 'uint32_t', 'a']]]])
 
     def test_mixed(self):
         src = """\
@@ -201,9 +201,9 @@
         ast = parser.parse(src)
         self.assertEquals(ast,
             [['metadata', 'version', '1'],
-             ['struct', 'foo', None, []],
+             ['struct', 'foo', [], None, []],
              ['metadata', 'version', '2'],
-             ['struct', 'bar', None, []]])
+             ['struct', 'bar', [], None, []]])
 
 class TestErrors(unittest.TestCase):
     def syntax_error(self, src, regex):