diff --git a/rosplan_knowledge_base/include/rosplan_knowledge_base/VALVisitorOperator.h b/rosplan_knowledge_base/include/rosplan_knowledge_base/VALVisitorOperator.h
index afae913fb..aa1df000e 100644
--- a/rosplan_knowledge_base/include/rosplan_knowledge_base/VALVisitorOperator.h
+++ b/rosplan_knowledge_base/include/rosplan_knowledge_base/VALVisitorOperator.h
@@ -36,6 +36,8 @@ namespace KCL_rosplan {
 		/* visitor methods */
 		virtual void visit_proposition(VAL1_2::proposition *);
 		virtual void visit_operator_(VAL1_2::operator_ *);
+    	virtual void visit_action(VAL1_2::action * s);
+    	virtual void visit_durative_action(VAL1_2::durative_action * s);
 
 		virtual void visit_simple_goal(VAL1_2::simple_goal *);
 		virtual void visit_qfied_goal(VAL1_2::qfied_goal *);
diff --git a/rosplan_knowledge_base/src/PDDLKnowledgeBase.cpp b/rosplan_knowledge_base/src/PDDLKnowledgeBase.cpp
index 959157581..559e91ccb 100644
--- a/rosplan_knowledge_base/src/PDDLKnowledgeBase.cpp
+++ b/rosplan_knowledge_base/src/PDDLKnowledgeBase.cpp
@@ -118,7 +118,7 @@ namespace KCL_rosplan {
         VAL1_2::operator_list* operators = domain_parser.domain->ops;
         for (VAL1_2::operator_list::const_iterator ci = operators->begin(); ci != operators->end(); ci++) {
             if((*ci)->name->symbol::getName() == req.name) {
-                op_visitor.visit_operator_(*ci);
+                (*ci)->visit(&op_visitor);
                 res.op = op_visitor.msg;
                 return true;
             }
diff --git a/rosplan_knowledge_base/src/VALVisitorOperator.cpp b/rosplan_knowledge_base/src/VALVisitorOperator.cpp
index cb3001d3b..24d37d1c6 100644
--- a/rosplan_knowledge_base/src/VALVisitorOperator.cpp
+++ b/rosplan_knowledge_base/src/VALVisitorOperator.cpp
@@ -4,6 +4,7 @@
 namespace KCL_rosplan {
 
     /* encoding state */
+    bool parsing_duration;
     bool cond_neg;
     bool eff_neg;
     VAL1_2::time_spec cond_time;
@@ -14,6 +15,19 @@ namespace KCL_rosplan {
     /* operators */
     /*-----------*/
 
+    void VALVisitorOperator::visit_durative_action(VAL1_2::durative_action * op) {
+        visit_operator_(op);
+        parsing_duration = true;
+        msg.instant_action = false;
+        op->dur_constraint->visit(this);
+        parsing_duration = false;
+    }
+
+    void VALVisitorOperator::visit_action(VAL1_2::action * op) {
+        visit_operator_(op);
+        msg.instant_action = true;
+    }
+
     /**
      * Visit an operator to pack into ROS message
      */
@@ -51,6 +65,7 @@ namespace KCL_rosplan {
         op->effects->visit(this);
 
         // conditions
+        parsing_duration = false;
         if (op->precondition) op->precondition->visit(this);
     }
 
@@ -143,6 +158,10 @@ namespace KCL_rosplan {
             case VAL1_2::E_EQUALS:  ineq.comparison_type = rosplan_knowledge_msgs::DomainInequality::EQUALS; break;
         }
 
+        if(parsing_duration) {
+            msg.duration = ineq;
+            return;
+        }
         switch(cond_time) {
             case VAL1_2::E_AT_START: msg.at_start_comparison.push_back(ineq); break;
             case VAL1_2::E_AT_END: msg.at_end_comparison.push_back(ineq); break;
diff --git a/rosplan_knowledge_msgs/msg/DomainOperator.msg b/rosplan_knowledge_msgs/msg/DomainOperator.msg
index fc1dcb741..01fd1e5c3 100644
--- a/rosplan_knowledge_msgs/msg/DomainOperator.msg
+++ b/rosplan_knowledge_msgs/msg/DomainOperator.msg
@@ -4,7 +4,8 @@
 rosplan_knowledge_msgs/DomainFormula formula
 
 # (2) duration constraint
-
+bool instant_action
+rosplan_knowledge_msgs/DomainInequality duration
 
 # (3) effect lists
 rosplan_knowledge_msgs/DomainFormula[] at_start_add_effects