• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.838-840
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• 1999

In this paper, modeling and analysis of discrete event systems by temporal logic frame works and petri net is considered. The reachability tree of the petri net can be used to solve the safeness, boundedness, conservation and coverability problems of discrete event systems. But the reachability tree of the petri net do not solve reachability and liveness problems in general. We proposed a method that synthesised the petri net and the temporal logic frameworks. This method slove some problems of petri net by logical representation of temporal logic frameworks.

• Journal of the Korea Society for Simulation
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• v.1 no.1
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• pp.37-47
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• 1992

This paper proposes an analysis method of petri nets(PNs) using the relational algebra(RA). More wpecifically, we represent PNs in relations of the relational model. Based on such representation, we first develop an algorithm for generating reachability trees of PNs. we then develop an algorithm for generating reachability trees of PNs. We then develop algorithms for analyzing properties of PNs, such as boundedness, conservation, coverability, reachability, and liveness. The advantage of this approach is as follows: First, the algorithms represented by RA can be easity converted to a query language such as SQL of the widely used, commerical relational database management systems(DBMSs). Second, we can alleviate the problem of state space explosion because relational DBMSs can handle large amounts of data efficiently. Finally, we can use the DBMS's query language to interpret the Petri nets and make simulation.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.745-752
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• 2005

BGP is a unique routing protocol in broadband internet. It chooses routing paths considering internet hierarchy and local policies. As BGP routers selectively bypass routing information to a subset of neighboring BGP routers, connectivity by way of a series of links between source and destination nodes does not mean reachability of routing information of the two. In emergency when BGP routers or links over wide range are not available, BGP routers have to use links that are not normally used to keep reachability. This paper listed out the requirements for BGP backup routing and proposed a routing solution that hides most demerits in currently published ones. The proposed backup operates in three tiers according to network damage. Under this rule, BGP routers use tier-0 routing paths at normal. If networks are impaired, they choose tier-1 paths. If networks are seriously damaged, tier-2 paths are allowed to use. Also this paper proves that the proposed backup guarantees stability and safeness. As results, the proposed backup is very adaptive to light network damages as well as serious ones and provides strong routing reachability at all times.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.956-963
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• 2008

In a multi-hop wireless ad hoc network broadcasting is an elementary operation to support route discovery, address resolution and other application tasks. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network which is referred to as the broadcast storm problem. Many broadcasting schemes have been proposed to give better performance than simple flooding in wireless ad hoc network. How to decide whether re-broadcast or not also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose enhanced broadcasting schemes, which can reduce re-broadcast packets without loss of reachability. Simulation results show that proposed schemes can offer better reachability as well as efficiency as compared to other previous schemes.

• Journal of Information Processing Systems
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• v.16 no.1
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• pp.201-209
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• 2020

The graph data structure is popular because it can intuitively represent real-world knowledge. Graph databases have attracted attention in academia and industry because they can be used to maintain graph data and allow users to mine knowledge. Mining reachability relationships between two nodes in a graph, termed reachability query processing, is an important functionality of graph databases. Online traversals, such as the breadth-first and depth-first search, are inefficient in processing reachability queries when dealing with large-scale graphs. Labeling schemes have been proposed to overcome these disadvantages. The state-of-the-art is the 2-hop labeling scheme: each node has in and out labels containing reachable node IDs as integers. Unfortunately, existing 2-hop labeling schemes generate huge 2-hop label sizes because they only consider local features, such as degrees. In this paper, we propose a more efficient 2-hop label size reduction approach. We consider the topological sort index, which is a global feature. A linear combination is suggested for utilizing both local and global features. We conduct experiments over real-world and synthetic directed acyclic graph datasets and show that the proposed approach generates smaller labels than existing approaches.

• 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.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.3
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• pp.173-181
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• 2012

The size and layout of user interface components need to be optimally designed in terms of reachability, visibility, clearance, and compatibility in order for efficient and effective use of products. The present study develops an ergonomic design method which optimizes the size and layout of user interface components using adaptive genetic algorithm. The developed design method determines a near-optimal design which maximizes the aggregated score of 4 ergonomic design criteria (reachability, visibility, clearance, and compatibility). The adaptive genetic algorithm used in the present study finds a near-optimum by automatically adjusting the key parameter (probability of mutation) of traditional genetic algorithm according to the characteristic of current solutions. Since the adaptive mechanism partially helps to overcome the local optimality problem, the probability of finding the near-optimum has been substantially improved. To evaluate the effectiveness of the developed design method, the present study applied it to the user interface design for a portable wireless communication radio.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.176-184
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• 2000

Possible representation methods for the product structure have been compared and analyzed to determine optimal disassembly path of a product. Petri net is selected as the most optimal method to represent disassembly path of the product. In this method, a reachability tree for the product is generated and disassembly time for each path is calculated. A path with the smallest disassembly time is selected as the optimal path. A software far DPN(Disassembly Petri Net) has been developed and applied to search the optimal disassembly path for a ballpoint pen disassembly process as an example.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1874-1885
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• 2000

When a receiver of ciphertext message can not decrypt a message because he has lost his private-key, the private-key of receiver and session-key of the message should be recovered. In this paper, we developed an Encapsulation based Key Recovery System (EKRS). EKRS is a new key encapsulation based key recovery system which is characterized by secretly choice of KRA, randomized target keys. n-way recovery type, and useful for commercial key recovery. EKRS is formally specified by a pictorial model, an Extended Cryptographic Timed Petri Net (ECTPN). Secure information flow and reachability of a session-key are verified by using reachability graph of ECTPN. EKRS, executing over a Public Key Infrastructure, can be used as a security solution in Web based applications such as CALS, EC an EDI.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.167-173
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• 2007

This paper describes a redundancy resolution based method for determining an optimal initial configuration of a humanoid robot for holding an object. There are three important aspects for a humanoid robot to be able to hold an object. Those three aspects are the reachability that guarantees the robot to reach the object, the stability that guarantees the robot to remain stable while moving or holding the object, and the manipulability that makes the robot manipulate the object dexterously. In this paper, a humanoid robot with 20 degrees of freedom is considered. The humanoid robot is kinematically redundant and has infinite number of solutions for the initial configuration problem. The complex three-dimensional redundancy resolution problem is divided into two simple two-dimensional redundancy resolution problems by incorporating the symmetry of the problem, robot's moving capability, and the geometrical characteristics of the given robot. An optimal solution with respect to the reachability, the stability, and the manipulability is obtained by solving these two redundancy resolution problems.