Life Science Journal 2012;9(4) http://www.lifesciencesite.com http://www.lifesciencesite.com lifesciencej@gmail.com 3094 Formal Analysis of Arrival Procedure of Air Traffic Control System Shahid Yousaf 1 , Sher Afzal Khan 2 , Nazir Ahmad Zafar 3 , Farooq Ahmad 1 , and Muazzam Ali Khan 2 1 Faculty of Information Technology, University of Central Punjab, Lahore, Pakistan 2 Department of Computer sciences, Abdul Wali Khan University, Mardan, Pakistan 3 Department of Computer Science, King Faisal University, Al Hassa, Saudi Arabia Email: shahid.yousaf@ucp.edu.pk; muazzam@awkum.edu.pk; drfarooq@ucp.edu.pk ; nazafar@kfu.edu.sa Abstract: The air traffic control (ATC) is safety, monetary and environmental critical system. Its failure may cause the loss of human life, severe injuries, loss of money and environmental issues. The complexity of such systems requires formal modeling and step by step design processes. In this paper we investigate the use of formal method VDM++ to specify and verify the arrival procedure of aircrafts. The control along arrival procedure changes from the ramp to the gate controller to make possible the safe arrival. For the specification the bottom up approach is used to model the system. Initially, aircraft, ramp and gate controller are specified, then all are combine for their synchronize approach. The specification and syntactical verification are performed by VDM++ which is an object oriented model based formal approach. [Yousaf S, Khan SA, Zafar NA and Farooq A and Khan MA. Formal Analysis of Arrival Procedure of Air Traffic Control System. Life Sci J 2012;9(4):3094-3098] (ISSN:1097-8135). http://www.lifesciencesite.com . 454 . Keywords: VDM++; air traffic control system; formal specification; formal method. 1. Introduction The major concern of air traffic control system is to ensure the safe operation of private and commercial aircrafts [5]. ATC is heavily dependent upon the capabilities of human operator; some accidents in ATC were documented by “human error” with the causal factor involving the perception, memory, decision making, communication and resource management [4]. Therefore formal analysis is very essential for proving safety properties of ATC system. Formal methods are used to remove the ambiguities in specification of system and have been applied to specify and verify the complex systems. The above mentioned reason motivated us to use formal methods to design ATC system. The work of S. Ahmad and V. Saxena [1] used the Sami formal notation UML which cannot be verified systematically to ensure a specification’s accuracy [9]. VDM++ has the following advantages to design air traffic control system. 1). This specification technique is more comprehensive form than other methods. 2) It gives a precise definition of what is going to build. 3) In our research, VDM++ helped to clarify the key ideas of ATC system. 4) It provided a precise way of defining the data and underlying functions of the ATC system. 5) It also provided us a way to specify the interface between components of the entire system under development in a precise manner. For the safe arrival process aircrafts communicate with the air traffic controllers. In this arrival procedure initially, the aircraft is under the control of ramp controller all the activities during arrival process of aircraft are controlled by this controller. Initially the aircraft will send request to the ramp controller for the entrance of ramp area and on this request the ramp controller grant the permission to aircraft then after this aircraft enter into ramp area. The gate controller arranged all the aircraft in sequence at ramp and then control is transfer to gate controller. Just likewise the ramp controller, gate controller controls the activities of aircraft. In this paper, we have used the extend version of Vienna Development Method (VDM) that is VDM++ to formalize the arrival procedure of aircraft. The organization of this paper is as fallow. In section 2, an introduction to formal methods is presented. Formal modeling of the arrival procedure is given using VDM++ in section 3. Finally, conclusion and future works is discussed in section 4. 2. Formal Methods Formal methods [13-15] consist of the set of techniques and tools based on mathematical modeling and formal logic that are used to specify and verify requirements and designs for computer systems and software as presented in various application [16-26] 2.1 Classification of Formal Methods Formal methods are used for both software and hardware designing or software- hardware co- designing [6, 10]. Classification of formal methods with respect to the use of it, is given below as discussed in [10]. Writing Formal Specification: Formal methods are used to reason about mathematical objects. However, hardware circuits are not mathematical objects, they are real world physical objects. Therefore, it is necessary to develop