diff --git a/src/main/java/org/bdware/server/trustedmodel/ContractExecutor.java b/src/main/java/org/bdware/server/trustedmodel/ContractExecutor.java
index 1cd23a9..a2f969e 100644
--- a/src/main/java/org/bdware/server/trustedmodel/ContractExecutor.java
+++ b/src/main/java/org/bdware/server/trustedmodel/ContractExecutor.java
@@ -5,9 +5,17 @@ import org.bdware.sc.conn.Node;
 import org.bdware.sc.conn.OnHashCallback;
 import org.bdware.sc.conn.ResultCallback;
 
+import java.util.Map;
+
 public interface ContractExecutor {
     void execute(String requestID, ContractRequest req, ResultCallback rcb, OnHashCallback hcb);
 
+    default void onRecover(Map<String, Object> args) {
+    }
+
+    default void onDeliverBlock(String data) {
+    }
+
     default void close() {
     }
 
diff --git a/src/main/java/org/bdware/server/trustedmodel/MultiReqSeq.java b/src/main/java/org/bdware/server/trustedmodel/MultiReqSeq.java
new file mode 100644
index 0000000..9a08e59
--- /dev/null
+++ b/src/main/java/org/bdware/server/trustedmodel/MultiReqSeq.java
@@ -0,0 +1,11 @@
+package org.bdware.server.trustedmodel;
+
+public class MultiReqSeq {
+    public final int seq;
+    public final long startTime;
+
+    public MultiReqSeq(int s){
+        seq = s;
+        startTime = System.currentTimeMillis();
+    }
+}