Formal specification and analysis of take-off procedure using VDM-SL

Abstract

Purpose Air traffic management system is a complex adaptive and safety critical system which requires considerable attention for its modelling and verification. Currently Air traffic control (ATC) systems are heavily dependent upon human intervention at airport causing accidents and delays because of failure of communication. The purpose of this study is to develop, plan, manage and verify aircrafts movement procedures at the airport surface that prevent delays and collisions. Methods The airport surface is decomposed into blocks and represented by the graph relation. The state space of the system is described by identifying all the possible components of the system. The ground and local controls monitor queues of the aircrafts moving from taxiway to take-off. It is insured that once an aircraft is inserted into a queue, it is eventually removed from it after the next queue has become available. The take-off procedure is provided using graph theory and Vienna Development Method Specification Language (VDM-SL) and analyzed using VDM-SL toolbox. Results Formal specification of graph-based model, taxiways, aircrafts, runways and controllers is provided in static part of the model. The state space analysis describing take-off algorithms is provided by defining optimal paths and possible operations in dynamic model expediting the departure procedure. The model is developed by a series of refinements following the stepwise development approach. Conclusions The delays at airport surface require effective safety and guidance protocols to control air traffic at the airport. In static model, the safety criteria are described in terms of invariants over the data types carrying critical information. The safety is insured by defining pre/post conditions in description of operations for changing state space of the system. Although the proposed study is focussed more on the safety component, however, the efficiency is not ignored.

Formal approach to model complex adaptive computing systems

“…The approach is applied to a boids model of self-organized flocking of animals monitored by a random deployment of proximity sensors. Zafar (2016) presented a formal specification of take-off procedure using Vienna Development Method-Specification Language VDM-SL complex adaptive systems modeling in order to overcome communication failures that cause delays and collisions. The presented model is developed by a series of refinements and made up of (i) a static part that includes the graph-based model, aircrafts, controllers, taxiways and runways, whereas, (ii) the dynamic part describe the take-off algorithms.…”

Hybrid subnet-based node failure recovery formal procedure in wireless sensor and actor networks

“…The connectivity of a subnet is verified by finding a path between any two nodes of the subnet (line 3-5). The connectivity of network is verified by finding a path between any two gateways of the network (line [6][7][8]. Initially, all the actors of the subnets are initialized as non-critical (lines 9 and 10).…”

“…Formal methods are mathematical notations which are effective for modeling, specifying and analyzing properties of safety, mission-critical systems, and complex systems. [5][6][7][8] Few preliminary results of our research are presented in Afzaal and Zafar. 9,10 Maintaining connectivity is an important issue because if a node fails, then network may be partitioned into disjoint segments.…”

Formal analysis of subnet-based failure recovery algorithm in wireless sensor and actor and network

“…CAS are defined as dynamic networks of a large number of agents, individuals, species, cells, nations, firms that act in parallel, act and react constantly to what the other agents do (Zafar 2016;Holland 2006). Examples of artificial CAS include artificial intelligence systems, evolutionary programs and artificial neural networks.…”

“…For the verification of CAS (Zafar 2016), most of the researchers focused on ABM and CN modeling which are based on testing and simulation techniques. These techniques cannot guarantee about the correctness of the systems because to gain a required level of confidence number of inputs for testing and simulations increases exponentially.…”