diff --git a/src/main/java/org/gcube/informationsystem/resourceregistry/api/rest/SharingPath.java b/src/main/java/org/gcube/informationsystem/resourceregistry/api/rest/SharingPath.java
index e65d102..232375e 100644
--- a/src/main/java/org/gcube/informationsystem/resourceregistry/api/rest/SharingPath.java
+++ b/src/main/java/org/gcube/informationsystem/resourceregistry/api/rest/SharingPath.java
@@ -6,4 +6,11 @@ public class SharingPath {
 	
 	public static final String CONTEXTS_PATH_PART = ContextPath.CONTEXTS_PATH_PART;
 	
+	public static final String OPERATION_QUERY_PARAMETER = "operation";
+	
+	public enum SharingOperation {
+		ADD,
+		REMOVE
+	}
+	
 }