• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.2
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• pp.115-118
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• 1991

Land information system is a data base describing physical or legal characteristics of land areas, sometimes called a land records system. The digital remote sensor data is useful to calculate some fundamental statistics of the spectral data. This normally involves computing the minimum and maximum value for each band imagery, the mean, the standard deviation, a variance-covariance matrix, and frequencies of brightness values in each channel which are used to produce histograms. In this paper, author emphasize scanning for aerial photos, and next paper will be scanning for satellite image.

• Asia pacific journal of information systems
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• v.1 no.1
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• pp.49-62
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• 1991

This paper examines the problems of database partitioning and file allocation in a fixed topology distributed computer network. The design objective is to make files as collections of attributes and to allocate these files to network nodes so that a minimum total transmission cost is achieved subject to storage capacity constraints. A mathematical model for solving the problem is formulated and, the resulting optimization problem is shown to fall in a class of NP-complete problems. A new heuristic algorithm is developed which uses the idea of allocating attributes according to the transaction requirements at each computer node and then making files using the allocated attributes. Numerical results indicate that the heuristic algorithm yields practicable low cost solutions in comparison with the existing methods which deal with the file allocation problems and database partitioning problems independently.

• Journal of KIISE:Databases
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• v.30 no.3
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• pp.310-319
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• 2003

Workflow is defined as the automation of a business process, and consists of interrelated workflow tasks. Because many modem business processes nay involve activities that are geographically distributed between different departments or organizations, workflow inherently has the characteristics of distribution. In distributed workflow systems, each workflow task performs its assigned role by utilizing information resources placed at some hosts, and then transmits workflow execution control to the next tasks in a workflow definition. Hence, it is very important to appropriately allocate workflow tasks to hosts for high performance workflow processing. In this paper, we propose a multilevel workflow graph partitioning scheme for efficient placement of workflow tasks. This method can improve the performance of workflow processing by minimizing the remote communication costs occurred during workflow execution.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.315-323
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• 2001

The concept of vertical partitioning has been discussed so far in an objective of improving the performance of query execution and system throughput. It can be applied to the areas where the match between data and queries affects performance, which includes partitioning of individual files in centralized environments, data distribution in distributed databases, dividing data among different levels of memory hierarchies, and so on. In general, a vertical partitioning algorithm should support n-ary partitioning as well as a globally optimal solution for the generation of all meaningful fragments. Most previous methods, however, have some limitations to support both of them efficiently. Because the vertical partitioning problem basically includes the fuzziness property, the proper management is required for the fuzziness problem. In this paper we propose an efficient vertical $\alpha$-partitioning algorithm which is based on the fuzzy theory. The method can not only generate all meaningful fragments but also support n-ary partitioning without any complex mathematical computations.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.395-405
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• 2001

In this paper, we analyze workflow management system in programming language aspects. Many workflow characteristics such as workflow relevant data, workflow control structures, and workflow application invocations are studied and compared with those of distributed parallel programs. Although there exist minor differences between them, we found that there exist surprisingly many analogies between them. Based on this observation, we suggest to view workflow management system as distributed parallel program development platform. This new view on workflow management system provides users consistent view on workflow and workflow management system and with this view workflow management system designer can cope with arbitrary requests from the users keeping design consistency. Moreover the analogy between workflow and program provides a basis to apply program analysis techniques to the analysis of workflow.

• Korean Journal of Remote Sensing
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• v.11 no.2
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• pp.1-16
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• 1995

This study is conducted to eveluate the potential of a GIS to assist an application problem. GIS has been applied to rainfall-runoff modeling over Soyang area. Various rainfall-runoff models have been developed over the years. A distributed rainfall-runoff model is selected because it considers the topographic characteristics over the basin. GIS can handle the spatial data to enhance the modeling. GRASS-a public domain GIS S/W-is used for GIS tools. Digital database is generated, including soil map, vegetation map, digital elevation model, basin and subbasin map, and water stream. The inpu data for the model has been generated and manupulated using GIS. The database, model and GIS are integrated for on-line operation. The inflow hydrographs are tested for the flood of Sept., 1990. This shows the promising results even without the calibration.

• Journal of KIISE:Databases
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• v.33 no.5
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• pp.437-452
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• 2006

In this paper, we propose an extended XPath specification which includes a special matching character '%' used in the LIKE operation of SQL in order to solve the difficulty of writing some queries to filter element contents well, using the previous XPath specification. We also present a novel technique for filtering a collection of document-centric XMLs, called Pfilter, which is able to exploit the extended XPath specification. Owing to sharing the common prefix characters of the operands in value-based predicates, the Pfilter improves the performance in processing those. We show several performance studies, comparing Pfilter with Yfilter in respect to efficiency and scalability as using multi-query processing time (MQPT), and reporting the results with respect to inserting, deleting, and processing of value-based predicates. In conclusion, our approach provides a core algorithm for evaluating the contains() function of XPath queries in previous XML filtering researches, and a foundation for building XML-based distributed information systems.

• Journal of KIISE:Information Networking
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• v.32 no.2
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• pp.261-277
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• 2005

We propose the PAD (Power Aware Data-centric Routing Protocol), which finds minimum energy routes and prolongs network life-time, for the data-centric sensor networks. Firstly, the PAD discovers the minimum energy Property graph by removing redundant communication links. The proposed a1gorithm to find the minimum energy property graph is faster, simpler and easier to implement than existing aIgorithms. Secondly, the PAD runs the DDBF (Distributed Data-centric Bellman-Ford Algorithm) to determine routing paths between a base node and all sensor nodes. The DDBF selves the drawbacks of the distributed bellman-ford algorithm, i.e. slow convergence and a possible cyclic routing path. Since the PAD is a fully distributed algorithm with low overhead, it can be used in various kinds of resource limited sensor network applications.

• Journal of KIISE:Databases
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• v.28 no.3
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• pp.484-493
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• 2001

As real-time database systems are extended to the distributed computing environment, the need to apply the existing real-time concurrency control schemes to the distributed computing environment has been made. In this paper we propose an efficient concurrency control scheme for distributed real-time database system. Our proposed scheme guarantees a transaction to commit at its maximum, reduces the restart of a transaction that is on the prepared commit phase, and minimizes the time of the lock holding. This is because it raises the priority of the transaction that is on the prepared commit phase in the distributed real-time computing environment. In addition, it reduces the waiting time of a transaction that owns borrowed data and improves the performance of the system, as a result of lending the data that the transaction with the raised priority holds. We compare the proposed scheme with DO2PL_PA(Distributed Optimistic Two-Phase Locking) and MIRROR(Managing Isolation in Replicated Real-time Object Repositories) protocol in terms of the arrival rate of transactions, the size of transactions, the write probability of transactions, and the replication degree of data in a firm-deadline real-time database system based on two-phase commit protocol. It is shown through the performance evaluation that our scheme outperforms the existing schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.661-669
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• 2004

As a large number of distributed systems becoming more popular, interoperability, portability and security are becoming major concerns of modern computing. CORBA and object-oriented database which provide transparency of network and database are increasingly being used as the basis for distributed system to solve these problems. The two methods can help accomplish assurance of security by using a method-based access control technique or an attribute-based access control technique. These methods also enhance the unavailability or inefficiency caused by the delay of access process and bottleneck of the network due to the complex instance-based access control. We propose a security model on the type information based access control system that can enhance both security and availability by separating the functions delivered from CORBA and object-oriented databases. We apply the access control model specifically to enhancement of security system and also perform a test to verify the security and availability of our model.