diff --git a/jsprit-core/src/main/java/jsprit/core/problem/job/Job.java b/jsprit-core/src/main/java/jsprit/core/problem/job/Job.java
index 0d27c0b5..22419b05 100644
--- a/jsprit-core/src/main/java/jsprit/core/problem/job/Job.java
+++ b/jsprit-core/src/main/java/jsprit/core/problem/job/Job.java
@@ -18,6 +18,7 @@ package jsprit.core.problem.job;
 
 
 import jsprit.core.problem.Capacity;
+import jsprit.core.problem.Skills;
 
 /**
  * Basic interface for all jobs.
@@ -40,5 +41,12 @@ public interface Job {
 	 * @return Capacity
 	 */
 	public Capacity getSize();
+
+    /**
+     * Returns required skills.
+     *
+     * @return
+     */
+    public Skills getRequiredSkills();
 	
 }
diff --git a/jsprit-core/src/main/java/jsprit/core/problem/job/Service.java b/jsprit-core/src/main/java/jsprit/core/problem/job/Service.java
index f4594ca5..87ad0a78 100644
--- a/jsprit-core/src/main/java/jsprit/core/problem/job/Service.java
+++ b/jsprit-core/src/main/java/jsprit/core/problem/job/Service.java
@@ -21,6 +21,7 @@ import java.util.HashSet;
 import java.util.Set;
 
 import jsprit.core.problem.Capacity;
+import jsprit.core.problem.Skills;
 import jsprit.core.problem.solution.route.activity.TimeWindow;
 import jsprit.core.util.Coordinate;
 
@@ -71,7 +72,7 @@ public class Service implements Job {
 		
 		protected Capacity capacity;
 		
-		protected Set<String> skills = new HashSet<String>();
+		protected Skills.Builder skillBuilder = Skills.Builder.newInstance();
 		
 		/**
 		 * Constructs the builder.
@@ -187,7 +188,7 @@ public class Service implements Job {
 		}
 
 		public Builder addSkill(String string) {
-			skills.add(string.toLowerCase());
+			skillBuilder.addSkill(string);
 			return this;
 		}
 		
@@ -208,7 +209,7 @@ public class Service implements Job {
 	
 	private final Capacity size;
 	
-	private final Set<String> skills;
+	private final Skills skills;
 
 	Service(Builder builder){
 		id = builder.id;
@@ -218,7 +219,7 @@ public class Service implements Job {
 		timeWindow = builder.timeWindow;
 		type = builder.type;
 		size = builder.capacity;
-		skills = builder.skills;
+		skills = builder.skillBuilder.build();
 	}
 
 	@Override
@@ -319,18 +320,9 @@ public class Service implements Job {
 	 * 
 	 * @return
 	 */
-	public Set<String> getRequiredSkills() {
-		return Collections.unmodifiableSet(skills);
-	}
-	
-	/**
-	 * Returns true if this contains requiredSkill. Not case sensitive.
-	 * 
-	 * @param requiredSkill
-	 * @return
-	 */
-	public boolean requiresSkill(String requiredSkill){
-		return skills.contains(requiredSkill.toLowerCase());
+	public Skills getRequiredSkills() {
+		return skills;
 	}
 	
+
 }
diff --git a/jsprit-core/src/main/java/jsprit/core/problem/job/Shipment.java b/jsprit-core/src/main/java/jsprit/core/problem/job/Shipment.java
index 0c94f6e8..3f3bd3c3 100644
--- a/jsprit-core/src/main/java/jsprit/core/problem/job/Shipment.java
+++ b/jsprit-core/src/main/java/jsprit/core/problem/job/Shipment.java
@@ -5,6 +5,7 @@ import java.util.HashSet;
 import java.util.Set;
 
 import jsprit.core.problem.Capacity;
+import jsprit.core.problem.Skills;
 import jsprit.core.problem.solution.route.activity.TimeWindow;
 import jsprit.core.util.Coordinate;
 
@@ -57,7 +58,7 @@ public class Shipment implements Job{
 		
 		private Capacity capacity;
 		
-		private Set<String> skills = new HashSet<String>();
+		private Skills.Builder skillBuilder = Skills.Builder.newInstance();
 		
 		/**
 		 * Returns new instance of this builder.
@@ -236,8 +237,8 @@ public class Shipment implements Job{
 			return new Shipment(this);
 		}
 
-		public Builder addSkill(String string) {
-			skills.add(string.toLowerCase());
+		public Builder addSkill(String skill) {
+			skillBuilder.addSkill(skill);
 			return this;
 		}
 
@@ -264,7 +265,7 @@ public class Shipment implements Job{
 	
 	private final Capacity capacity;
 	
-	private final Set<String> skills;
+	private final Skills skills;
 
 	
 	/**
@@ -283,7 +284,7 @@ public class Shipment implements Job{
 		this.deliveryServiceTime = builder.deliveryServiceTime;
 		this.deliveryTimeWindow = builder.deliveryTimeWindow;
 		this.capacity = builder.capacity;
-		this.skills = builder.skills;
+		this.skills = builder.skillBuilder.build();
 	}
 	
 	@Override
@@ -400,11 +401,8 @@ public class Shipment implements Job{
 		return capacity;
 	}
 
-	public Set<String> getRequiredSkills() {
-		return Collections.unmodifiableSet(skills);
-	}
-	
-	public boolean requiresSkill(String requiredSkill){
-		return skills.contains(requiredSkill.toLowerCase());
+	public Skills getRequiredSkills() {
+		return skills;
 	}
+
 }