diff --git a/YangParser/SemanticModel/Action.cs b/YangParser/SemanticModel/Action.cs
new file mode 100644
index 0000000..a14e633
--- /dev/null
+++ b/YangParser/SemanticModel/Action.cs
@@ -0,0 +1,31 @@
+using System;
+using System.Linq;
+
+namespace YangParser.SemanticModel;
+
+public class Action : Statement
+{
+    
+    public Action(YangStatement statement)
+    {
+        if (statement.Keyword != Keyword)
+            throw new InvalidOperationException($"Non-matching Keyword '{statement.Keyword}', expected {Keyword}");
+        Argument = statement.Argument!.ToString();
+        ValidateChildren(statement);
+        Children = statement.Children.Select(StatementFactory.Create).ToArray();
+    }
+
+    public const string Keyword = "action";
+
+    public override ChildRule[] PermittedChildren { get; } =
+    [
+        new ChildRule(Description.Keyword),
+        new ChildRule(Grouping.Keyword, Cardinality.ZeroOrMore),
+        new ChildRule(FeatureFlag.Keyword, Cardinality.ZeroOrMore),
+        new ChildRule(Input.Keyword),
+        new ChildRule(Output.Keyword),
+        new ChildRule(Reference.Keyword),
+        new ChildRule(Status.Keyword),
+        new ChildRule(TypeDefinition.Keyword, Cardinality.ZeroOrMore),
+    ];
+}
\ No newline at end of file
diff --git a/YangParser/SemanticModel/Builtins/BuiltinType.cs b/YangParser/SemanticModel/Builtins/BuiltinType.cs
new file mode 100644
index 0000000..f7f9b38
--- /dev/null
+++ b/YangParser/SemanticModel/Builtins/BuiltinType.cs
@@ -0,0 +1,45 @@
+namespace YangParser.SemanticModel.Builtins;
+
+public class BuiltinType(string name, string? correspondingCSharpType)
+{
+    public string Name => name;
+    public string? CorrespondingCSharpType => correspondingCSharpType;
+}
+
+public class Binary() : BuiltinType("binary", "byte[]");
+
+public class Bits() : BuiltinType("bits", null);
+
+public class Boolean() : BuiltinType("boolean", "bool");
+
+public class Decimal64() : BuiltinType("decimal64", "double");
+
+public class Empty() : BuiltinType("empty", null);
+
+public class Enumeration() : BuiltinType("enumeration", "enum");
+
+public class IdentityReference() : BuiltinType("identityref", null);
+
+public class InstanceIdentifier() : BuiltinType("instance-identifier", null);
+
+public class Int8() : BuiltinType("int8", "sbyte");
+
+public class Int16() : BuiltinType("int16", "short");
+
+public class Int32() : BuiltinType("int32", "int");
+
+public class Int64() : BuiltinType("int64", "long");
+
+public class LeafReference() : BuiltinType("leafref", null);
+
+public class String() : BuiltinType("string", "string");
+
+public class Uint8() : BuiltinType("uint8", "byte");
+
+public class Uint16() : BuiltinType("uint16", "ushort");
+
+public class Uint32() : BuiltinType("uint32", "uint");
+
+public class Uint64() : BuiltinType("uint64", "ulong");
+
+public class Union() : BuiltinType("union", null);
\ No newline at end of file
diff --git a/YangParser/SemanticModel/Rpc.cs b/YangParser/SemanticModel/Rpc.cs
index cc0ce91..9f852ee 100644
--- a/YangParser/SemanticModel/Rpc.cs
+++ b/YangParser/SemanticModel/Rpc.cs
@@ -19,12 +19,12 @@ public Rpc(YangStatement statement)
     public override ChildRule[] PermittedChildren { get; } =
     [
         new ChildRule(Description.Keyword),
-        new ChildRule(Grouping.Keyword),
-        new ChildRule(FeatureFlag.Keyword),
+        new ChildRule(Grouping.Keyword, Cardinality.ZeroOrMore),
+        new ChildRule(FeatureFlag.Keyword, Cardinality.ZeroOrMore),
         new ChildRule(Input.Keyword),
         new ChildRule(Output.Keyword),
         new ChildRule(Reference.Keyword),
-        new ChildRule(StateData.Keyword),
-        new ChildRule(TypeDefinition.Keyword),
+        new ChildRule(Status.Keyword),
+        new ChildRule(TypeDefinition.Keyword, Cardinality.ZeroOrMore),
     ];
 }
\ No newline at end of file