diff --git a/PDDL/Model/PDDL12/EffectKind.cs b/PDDL/Model/PDDL12/EffectKind.cs
new file mode 100644
index 0000000..b60d232
--- /dev/null
+++ b/PDDL/Model/PDDL12/EffectKind.cs
@@ -0,0 +1,29 @@
+namespace PDDL.Model.PDDL12
+{
+    /// <summary>
+    /// Class ListType.
+    /// </summary>
+    public enum EffectKind
+    {
+        /// <summary>
+        /// The effect is negated. This is typically the
+        /// case with the remove list.
+        /// </summary>
+        Negated = -1,
+        
+        /// <summary>
+        /// No effect
+        /// </summary>
+        None = 0,
+        
+        /// <summary>
+        /// The effect is added.
+        /// </summary>
+        Regular = 1,
+
+        /// <summary>
+        /// This is a composite effect.
+        /// </summary>
+        Conjunction = 1
+    }
+}
diff --git a/PDDL/Model/PDDL12/Effects/ConjunctionEffect.cs b/PDDL/Model/PDDL12/Effects/ConjunctionEffect.cs
index c19ac56..9955a25 100644
--- a/PDDL/Model/PDDL12/Effects/ConjunctionEffect.cs
+++ b/PDDL/Model/PDDL12/Effects/ConjunctionEffect.cs
@@ -21,7 +21,7 @@ public class ConjunctionEffect : EffectBase, IConjunctionEffect
         /// <param name="effects">The effects.</param>
         /// <exception cref="ArgumentNullException">The value of 'effects' cannot be null. </exception>
         public ConjunctionEffect([NotNull] IReadOnlyList<IEffect> effects)
-            : base(ListType.Indifferent)
+            : base(EffectKind.Conjunction)
         {
             if (ReferenceEquals(effects, null)) throw new ArgumentNullException("effects", "effects must not be null");
             Effects = effects;
diff --git a/PDDL/Model/PDDL12/Effects/EffectBase.cs b/PDDL/Model/PDDL12/Effects/EffectBase.cs
index c4de48d..82aa521 100644
--- a/PDDL/Model/PDDL12/Effects/EffectBase.cs
+++ b/PDDL/Model/PDDL12/Effects/EffectBase.cs
@@ -9,13 +9,13 @@ public abstract class EffectBase : IEffect
         /// Gets the list type.
         /// </summary>
         /// <value>The list type.</value>
-        public ListType Type { get; private set; }
+        public EffectKind Type { get; private set; }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="EffectBase"/> class.
         /// </summary>
         /// <param name="type">The type.</param>
-        protected EffectBase(ListType type)
+        protected EffectBase(EffectKind type)
         {
             Type = type;
         }
diff --git a/PDDL/Model/PDDL12/Effects/NegatedEffect.cs b/PDDL/Model/PDDL12/Effects/NegatedEffect.cs
index bfb8c37..d79a994 100644
--- a/PDDL/Model/PDDL12/Effects/NegatedEffect.cs
+++ b/PDDL/Model/PDDL12/Effects/NegatedEffect.cs
@@ -20,7 +20,7 @@ public class NegatedEffect : EffectBase, INegatedEffect
         /// <param name="effects">The effects.</param>
         /// <exception cref="ArgumentNullException">The value of 'effects' cannot be null. </exception>
         public NegatedEffect([NotNull] IAtomicFormula<ITerm> effects)
-            : base(ListType.Remove)
+            : base(EffectKind.Negated)
         {
             if (ReferenceEquals(effects, null)) throw new ArgumentNullException("effects", "effects must not be null");
             Effects = effects;
diff --git a/PDDL/Model/PDDL12/Effects/RegularEffect.cs b/PDDL/Model/PDDL12/Effects/RegularEffect.cs
index 687c747..d2209b9 100644
--- a/PDDL/Model/PDDL12/Effects/RegularEffect.cs
+++ b/PDDL/Model/PDDL12/Effects/RegularEffect.cs
@@ -20,7 +20,7 @@ public class RegularEffect : EffectBase, IRegularEffect
         /// <param name="effects">The effects.</param>
         /// <exception cref="ArgumentNullException">The value of 'effects' cannot be null. </exception>
         public RegularEffect([NotNull] IAtomicFormula<ITerm> effects)
-            : base(ListType.Add)
+            : base(EffectKind.Regular)
         {
             if (ReferenceEquals(effects, null)) throw new ArgumentNullException("effects", "effects must not be null");
             Effects = effects;
diff --git a/PDDL/Model/PDDL12/IEffect.cs b/PDDL/Model/PDDL12/IEffect.cs
index 2d0df4c..1395e51 100644
--- a/PDDL/Model/PDDL12/IEffect.cs
+++ b/PDDL/Model/PDDL12/IEffect.cs
@@ -12,7 +12,7 @@ public interface IEffect
         /// Gets the list type.
         /// </summary>
         /// <value>The list type.</value>
-        ListType Type { get; }
+        EffectKind Type { get; }
     }
 
     /// <summary>
diff --git a/PDDL/Model/PDDL12/ListType.cs b/PDDL/Model/PDDL12/ListType.cs
deleted file mode 100644
index 00b6a17..0000000
--- a/PDDL/Model/PDDL12/ListType.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-namespace PDDL.Model.PDDL12
-{
-    /// <summary>
-    /// Class ListType.
-    /// </summary>
-    public enum ListType
-    {
-        /// <summary>
-        /// Remove list
-        /// </summary>
-        Remove = -1,
-        
-        /// <summary>
-        /// Indifferent
-        /// </summary>
-        Indifferent = 0,
-        
-        /// <summary>
-        /// Add list
-        /// </summary>
-        Add = 1
-    }
-}
diff --git a/PDDL/Model/PDDL12/Null/NullEffect.cs b/PDDL/Model/PDDL12/Null/NullEffect.cs
index a75536c..5cda20a 100644
--- a/PDDL/Model/PDDL12/Null/NullEffect.cs
+++ b/PDDL/Model/PDDL12/Null/NullEffect.cs
@@ -24,7 +24,7 @@ public sealed class NullEffect : EffectBase
         /// <summary>
         /// Initializes a new instance of the <see cref="NullEffect"/> class.
         /// </summary>
-        public NullEffect() : base(ListType.Indifferent)
+        public NullEffect() : base(EffectKind.None)
         {
         }
     }
diff --git a/PDDL/PDDL.csproj b/PDDL/PDDL.csproj
index b7d6749..cc21214 100644
--- a/PDDL/PDDL.csproj
+++ b/PDDL/PDDL.csproj
@@ -88,7 +88,7 @@
     <Compile Include="Model\PDDL12\IPredicate.cs" />
     <Compile Include="Model\PDDL12\Predicate.cs" />
     <Compile Include="Model\PDDL12\Requirement.cs" />
-    <Compile Include="Model\PDDL12\ListType.cs" />
+    <Compile Include="Model\PDDL12\EffectKind.cs" />
     <Compile Include="Model\PDDL12\Effects\ConjunctionEffect.cs" />
     <Compile Include="Model\PDDL12\Effects\RegularEffect.cs" />
     <Compile Include="Model\PDDL12\Effects\EffectBase.cs" />
diff --git a/PDDL/Parser/PDDL12/EffectGrammar.cs b/PDDL/Parser/PDDL12/EffectGrammar.cs
index 06e51e0..b3fb49a 100644
--- a/PDDL/Parser/PDDL12/EffectGrammar.cs
+++ b/PDDL/Parser/PDDL12/EffectGrammar.cs
@@ -39,7 +39,7 @@ private static Parser<IEffect> CreateEffect()
         {
             Parser<IEffect> positiveEffect =
                 (from af in CommonGrammar.AtomicFormulaOfTerm
-                 select new AddEffect(af)).Token();
+                 select new RegularEffect(af)).Token();
 
             Parser<IEffect> negativeEffect =
                 (
@@ -47,7 +47,7 @@ from open in CommonGrammar.OpeningParenthesis
                     from keyword in Keywords.Not
                     from af in CommonGrammar.AtomicFormulaOfTerm
                     from close in CommonGrammar.ClosingParenthesis
-                    select new RemoveEffect(af)).Token();
+                    select new NegatedEffect(af)).Token();
 
             Parser<IEffect> conjunctionEffect =
                 (