diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/AbstractSyntaxTree.java b/src/main/java/de/ids_mannheim/korap/query/serialize/AbstractSyntaxTree.java
index 0f320a5..feeb503 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/AbstractSyntaxTree.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/AbstractSyntaxTree.java
@@ -71,6 +71,20 @@
 		return term;
 	}
 	
+	protected LinkedHashMap<String, Object> makeDoc() {
+		LinkedHashMap<String, Object> term = new LinkedHashMap<String, Object>();
+		term.put("@type", "korap:doc");
+		return term;
+	}
+	
+	protected LinkedHashMap<String, Object> makeDocGroup(String relation) {
+		LinkedHashMap<String, Object> term = new LinkedHashMap<String, Object>();
+		term.put("@type", "korap:docGroup");
+		term.put("relation", "relation:"+relation);
+		term.put("operands", new ArrayList<Object>());
+		return term;
+	}
+	
 	protected LinkedHashMap<String, Object> makeToken() {
 		LinkedHashMap<String, Object> token = new LinkedHashMap<String, Object>();
 		token.put("@type", "korap:token");