• Journal of KIISE:Computer Systems and Theory
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• v.26 no.12
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• pp.1485-1492
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• 1999

대규모 시스템 명세의 올바름을 검증하기 위한 유한 상태 LTS에 기반을 둔 CTL논리 적용에 있어 가장 큰 문제점은, 시스템 내부의 병렬 프로세스간의 상호작용으로 인한 상태폭발이다. 그러나 Modal mu-calculus 논리를 시스템 안전성 및 필연성 특성 명세에 사용하면, 행위에 의한 순환적 정의가 가능하므로 상태폭발 문제가 해결 가능하다. 본 논문에서는 LTS로 명세화된 통신 프로토콜 시스템 모델의 안전성 및 필연성 특성을 모형 검사 기법에 의해 검증함에 있어, 시제 논리로 사용된 Modal mu-calculus 안전성 및 필연성 논리식과 CTL 의 안전성 및 필연성 논리식의 극한값이 동일함을 두 논리식을 만족하는 상태 집합이 같다는 것을 보임으로써 증명한다. 증명된 결과는 I/O FSM 모델로 표현된 통신 프로토콜의 안전성 및 필연성 검사를 위해 이론적인 기반으로서, 컴퓨터를 이용한 모형검사 기법에 효과적인 방법으로 응용이 가능하다.Abstract In applying CTL-based model checking approach to correctness verification of large state transition system specifications, the major obstacle is the combinational explosion of the state space arising due to interaction of many loosely coupled parallel processes. If, however, the modal mu-calculus viewed as a CTL-based logic with recursion, is used to specify the safety and liveness property of a given system, it is possible to resolve this problem. In this paper, we discuss the problem of verifying communication protocol system specified in LTS, and prove that a logic expression specifying safety and liveness in modal mu-calculus is semantically identical to the maximum value of the expression in CTL. This relation is verified by the proof that the sets of states satisfying the two logic expressions are equivalent. The proof can be used as a theoretical basis for verifying safety and liveness of communication protocols represented as I/O FSM model.

• Journal of Korea Multimedia Society
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• v.8 no.8
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• pp.1119-1133
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• 2005

As a very important part in development of the protocol, verification and conformance test for protocol specification are complementary techniques that are used to increase the level of confidence in the system functions as prescribed by their specifications. In this paper, we verify the safety and liveness properties of rail signal control protocol type 1 specified in LTS with model checking method, and experimentally prove that it is possible to check for the deadlock, livelock and rechability of the states and actions on LTS. The implemented formal checker is able to verify whether properties expressed in modal logic are true in specifications using modal mu-calculus. We also propose a formal method on generation of conformance test cases using the concept of UIO sequences from verified protocol specification. The suggested tools are implemented by C++ language under Windows NT.

• The Transactions of the Korea Information Processing Society
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• v.5 no.4
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• pp.995-1004
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• 1998

This paper presents an implementation of model checking tool for LTS process specification, which checks deadlock, livelock and reachability for the state and action. The implemented formal checker using modal mu-calculus is able to verify whether properties expressed in modal logic are true on specifications. We prove experimentally that it is powerful to check, safety and liveness for the state and action on LTS. The tool is implemented by $C^{++}$ language and runs on IBM PC under Windows NT.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.354-357
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• 2004

According to the computerization of railway signaling systems, the interface link between the signaling systems has been replaced by the digital communication channel. At the same time, the importance of the communication link is more pronounced than in the past. In this paper, new network-based protocol for Korean railway signaling has designed between CTC and SCADA system, and the overview of designed protocol is briefly represented. Using the informal method for specifying the communication protocol, a little ambiguity may be contained in the protocol. To clear the ambiguity contained in the designed protocol, we use LTS model to design the protocol for this interface link between CTC and SCADA, the LTS is an intermediate model for encoding the operational behavior of processes. And then, we verify automatically and formally the safety and the liveness properties through the model checking method. Especially, the modal ${\mu}$-calculus, which is a highly expressive method of temporal logic that has been applied to the model checking method. It will be expected to increase the safety, reliability and efficiency of maintenance of the signaling systems by using the designed protocol for railway signaling in Korea.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.598-600
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• 2001

본 논문에서는 양상 뮤 논리를 위한 속성 명세 패턴 연구를 통해 시제 논리에 대한 패턴 기반의 단일한 프레임워크를 제시한다. 본 연구에서는 Dwyer의 속성 명세 패턴 분류를 상태(S)와 행동(A)으로 세분화하고 이를 다시 강함(A)와 약함(E)으로 다시 세분했다. 이러한 의미 기반의 계층적 패턴 분류 체계를 통해 양상 뮤 논리의 속성 명세 패턴을 분석했으며 실제 모형 검사기에서 사용된 예제들의 패턴 분류에 적용했다. 그 결과 기존의 분류 체계보다 더 정확한 분류가 가능했을 뿐만 아니라, 속성 명세의 작성 및 이해가 용이하였다.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.454-457
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• 2003

대규모 시스템 명세의 올바름을 검증하기 위한 유한상태 LTS(Labeled Transition System)에 기반을 둔 CTL(Computation Tree Logic) 논리 적용의 문제점은 시스템 내부의 병렬 프로세스간 상호 작용으로 인한 상태폭발이다. 그러나 medal mu-calculus 논리를 시스템 안전성 및 필연성 특성 명세에 사용하면, 행위에 의한 순환적 정의가 가능하므로 상태폭발 문제가 해결된다. 본 논문에서는 LTS 로 명세화 된 철도 신호제어용 프로토콜 모델의 안전성 및 필연성 특성을 모형 검사 기법에 의해 검증하기 위해 시제 논리로 사용된 modal mu-calculus를 사용하여 해당 검정 알고리즘을 구현 및 적용하였다.

• Journal of Korea Multimedia Society
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• v.3 no.1
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• pp.77-90
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• 2000

Real-Time verification is a procedure that verifies the correctness of specification related to requirement in time as well as in logic. One serious problem encountered in the verification task is that the state space grows exponentially owing to the unboundedness of time, which is termed the state space explosion problem. In this paper, we propose a real-time verification technique checking the correctness of specification by showing that a system model described in timed automata is equivalent to the characteristic of system property specified in timed modal-mu calculus. For this, we propose a local model checking method based on the value of the formula in initial state with constructing product graph concerned to only the nodes needed for verification process. Since this method does not search for every state of system model, the state space is reduced drastically so that the proposed method can be applied effectively to real-time system verification.

• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.513-519
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• 2006

As a very important part in development of the protocol, verifications for developed protocol specification are complementary techniques that are used to increase the level of confidence in the system functions by their specifications. Using the informal method for specifying the protocol, some ambiguity may be contained therein. This indwelling ambiguity in control systems can cause the occurrence of accidents, especially in the case of safety-critical systems. To clear the vagueness contained in the designed protocol, we use the LTS (Labeled Transition System) model to design the protocol for railway signaling. And then, we verify the safety and the liveness properties formally through the model checking method. The modal ${\mu}$-calculus, which is an expressive method of temporal logic, has been applied to the model checking method. We verify the safety and liveness properties of Korean standard protocol for railway signaling systems. To perform automatic verification of the safety and liveness properties of the designed protocol, a communication verification tool is implemented. The developed tools are implemented by C++ language under Windows XP. It is expected to increase the safety and reliability of communication protocol for signaling systems by using the developed communication verification tool.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.6
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• pp.380-387
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• 2004

In accordance with the computerization of railway signaling systems, the interface link between the signaling systems has been replaced by a digital communication channel. At the same time, the importance of the communication link has become increasingly significant. However, there are some questionable matters in the current state of railway signaling systems in KNR. First, different communication protocols have been applied to create an interface between railway signaling systems although the protocols have the same functions. Next, the communication protocols currently used in the railway fields have some illogical parts such as structure, byte formation, error correction scheme, and so on. To solve these matters, the standard communication protocol for railway signaling systems is designed. The newly designed protocol is overviews in this paper. And the simulation is performed to analysis the performance of data link control for designed protocol. According to this simulation, it is identified that the link throughput of new protocol is improved about 10% and the frame error rate is improved than existing protocol. And it is verified the safety and liveness properties of designed protocol by using a formal method for specifying the designed protocol. It is expected that there will be an increase in safety, reliability and efficiency in terms of the maintenance of the signaling systems by using the designed communication protocol for railway signaling.