diff --git a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/AbstractTextFilter.java b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/AbstractTextFilter.java
index b3305fe..746e8cb 100644
--- a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/AbstractTextFilter.java
+++ b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/AbstractTextFilter.java
@@ -111,7 +111,11 @@
 	
 	@Override
 	public boolean match(SpecElementWithAttributes element) {
-
+		if (operator == Operator.IS_SET || operator == Operator.IS_NOT_SET){
+			return super.match(element);
+		}
+		
+		
 		String theValue;
 
 		// retrieve the value to check depending on this is a filter on an
diff --git a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/BoolFilter.java b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/BoolFilter.java
index 4df6694..1841666 100644
--- a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/BoolFilter.java
+++ b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/BoolFilter.java
@@ -52,7 +52,11 @@
 
 	@Override
 	public boolean match(SpecElementWithAttributes element) {
-
+		if (operator == Operator.IS_SET || operator == Operator.IS_NOT_SET){
+			return super.match(element);
+		}
+		
+		
 		Boolean theValue;
 
 		AttributeValueBoolean attributeValue = (AttributeValueBoolean) ReqIF10Util.getAttributeValue(element, attributeDefinition);
diff --git a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/EnumFilter.java b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/EnumFilter.java
index 9783c34..f570c08 100644
--- a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/EnumFilter.java
+++ b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/EnumFilter.java
@@ -56,8 +56,10 @@
 		this.attributeDefinition = attributeDefinition;
 		this.operator = operator;
 		this.filterValues =  new HashSet<EnumValue>(value);
-		if (attributeDefinition.getDefaultValue() != null) {
+		if (attributeDefinition.getDefaultValue() != null){
 			this.defaultValues = new HashSet<EnumValue>(attributeDefinition.getDefaultValue().getValues());
+		}else{
+			this.defaultValues = new HashSet<EnumValue>();
 		}
 	}
 
@@ -65,6 +67,10 @@
 
 	@Override
 	public boolean match(SpecElementWithAttributes element) {	
+		if (operator == Operator.IS_SET || operator == Operator.IS_NOT_SET){
+			return super.match(element);
+		}
+		
 		AttributeValueEnumeration attributeValue = (AttributeValueEnumeration) ReqIF10Util.getAttributeValue(element, attributeDefinition);
 		
 		boolean useDefaultValue;
diff --git a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/NumberFilter.java b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/NumberFilter.java
index f45aa75..3dd4337 100644
--- a/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/NumberFilter.java
+++ b/org.eclipse.rmf.reqif10.search/src/org/eclipse/rmf/reqif10/search/filter/NumberFilter.java
@@ -101,6 +101,11 @@
 
 	@Override
 	public boolean match(SpecElementWithAttributes element) {
+		if (operator == Operator.IS_SET || operator == Operator.IS_NOT_SET){
+			return super.match(element);
+		}
+		
+		
 		Number theValue = getTheValue(element);