diff --git a/agent/src/main/java/li/strolch/search/ExpressionsSupport.java b/agent/src/main/java/li/strolch/search/ExpressionsSupport.java
index eab80318f..6f50a1509 100644
--- a/agent/src/main/java/li/strolch/search/ExpressionsSupport.java
+++ b/agent/src/main/java/li/strolch/search/ExpressionsSupport.java
@@ -1,10 +1,5 @@
 package li.strolch.search;
 
-import static li.strolch.model.StrolchModelConstants.*;
-
-import java.util.function.Function;
-import java.util.function.Supplier;
-
 import li.strolch.model.*;
 import li.strolch.model.activity.Activity;
 import li.strolch.model.parameter.Parameter;
@@ -12,6 +7,11 @@ import li.strolch.model.parameter.StringParameter;
 import li.strolch.persistence.api.StrolchTransaction;
 import li.strolch.utils.iso8601.ISO8601FormatFactory;
 
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import static li.strolch.model.StrolchModelConstants.*;
+
 /**
  * Implements search expressions to be statically imported when writing searches
  */
@@ -148,6 +148,13 @@ public class ExpressionsSupport {
 		};
 	}
 
+	public static <T extends StrolchRootElement> ExpressionBuilder extract(Function<T, Object> extractor) {
+		return element -> {
+			@SuppressWarnings("unchecked") T e = (T) element;
+			return extractor.apply(e);
+		};
+	}
+
 	public static <T extends StrolchRootElement> SearchExpression<T> paramNull(String paramId) {
 		return paramNull(BAG_PARAMETERS, paramId);
 	}
diff --git a/agent/src/main/java/li/strolch/search/SearchExpressions.java b/agent/src/main/java/li/strolch/search/SearchExpressions.java
index 02b70e2f1..70d56bd7d 100644
--- a/agent/src/main/java/li/strolch/search/SearchExpressions.java
+++ b/agent/src/main/java/li/strolch/search/SearchExpressions.java
@@ -1,17 +1,17 @@
 package li.strolch.search;
 
-import static li.strolch.model.StrolchModelConstants.BAG_PARAMETERS;
-import static li.strolch.model.StrolchModelConstants.BAG_RELATIONS;
-
-import java.util.function.Function;
-import java.util.function.Supplier;
-
 import li.strolch.model.Order;
 import li.strolch.model.Resource;
 import li.strolch.model.StrolchRootElement;
 import li.strolch.model.activity.Activity;
 import li.strolch.persistence.api.StrolchTransaction;
 
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import static li.strolch.model.StrolchModelConstants.BAG_PARAMETERS;
+import static li.strolch.model.StrolchModelConstants.BAG_RELATIONS;
+
 /**
  * Declares specific search expressions, i.e. extracting the relevant data for a where clause
  */
@@ -77,6 +77,10 @@ public interface SearchExpressions {
 		return ExpressionsSupport.param(BAG_PARAMETERS, paramId);
 	}
 
+	default <T extends StrolchRootElement> ExpressionBuilder extract(Function<T, Object> extractor) {
+		return ExpressionsSupport.extract(extractor);
+	}
+
 	default ExpressionBuilder relation(String paramId) {
 		return ExpressionsSupport.param(BAG_RELATIONS, paramId);
 	}