diff --git a/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Attribute.java b/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Attribute.java
index 2082020..6eec94f 100644
--- a/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Attribute.java
+++ b/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Attribute.java
@@ -1,26 +1,50 @@
 package org.monarchinitiative.owlsim.model.kb;
 
+import java.util.Objects;
+
 /**
  * @author cjm
  *
  */
 public class Attribute implements SimpleObject {
 
-	private String id;
-	private String label;
+	private final String id;
+	private final String label;
 	
 	public Attribute(String id, String label) {
-		super();
 		this.id = id;
 		this.label = label;
 	}
 
+	@Override
 	public String getId() {
 		return id;
 	}
 	
+	@Override
 	public String getLabel() {
 		return label;
 	}
-	
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		Attribute attribute = (Attribute) o;
+		return Objects.equals(id, attribute.id) &&
+				Objects.equals(label, attribute.label);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(id, label);
+	}
+
+	@Override
+	public String toString() {
+		return "Attribute{" +
+				"id='" + id + '\'' +
+				", label='" + label + '\'' +
+				'}';
+	}
 }
diff --git a/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Entity.java b/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Entity.java
index af32f80..06a5b2c 100644
--- a/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Entity.java
+++ b/owlsim-core/src/main/java/org/monarchinitiative/owlsim/model/kb/Entity.java
@@ -1,34 +1,50 @@
 package org.monarchinitiative.owlsim.model.kb;
 
+import java.util.Objects;
+
 /**
  * @author cjm
  *
  */
 public class Entity implements SimpleObject {
 	
-	private String id;
-	private String label;
+	private final String id;
+	private final String label;
 	
 	public Entity(String id, String label) {
-		super();
 		this.id = id;
 		this.label = label;
 	}
 
-	public void setId(String id) {
-		this.id = id;
-	}
-
-	public void setLabel(String label) {
-		this.label = label;
-	}
-
+	@Override
 	public String getId() {
 		return id;
 	}
 	
+	@Override
 	public String getLabel() {
 		return label;
 	}
-	
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (o == null || getClass() != o.getClass()) return false;
+		Entity entity = (Entity) o;
+		return Objects.equals(id, entity.id) &&
+				Objects.equals(label, entity.label);
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(id, label);
+	}
+
+	@Override
+	public String toString() {
+		return "Entity{" +
+				"id='" + id + '\'' +
+				", label='" + label + '\'' +
+				'}';
+	}
 }