• The KIPS Transactions:PartD
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• v.10D no.7
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• pp.1149-1154
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• 2003

Due to various requirements for the user access control to large databases in the hospitals and the banks, database security has been emphasized. There are many security models for database systems using wide variety of policy-based access control methods. However, they are not functionally enough to meet the requirements for the complicated and various types of access control. In this paper, we propose a database security system that can individually control user access to data groups of various sites and is suitable for the situation where the user's access privilege to arbitrary data is changed frequently. Data group(s) in different sixes d is defined by the table name(s), attribute(s) and/or record key(s), and the access privilege is defined by security levels, roles and polices. The proposed system operates in two phases. The first phase is composed of a modified MAC (Mandatory Access Control) model and RBAC (Role-Based Access Control) model. A user can access any data that has lower or equal security levels, and that is accessible by the roles to which the user is assigned. All types of access mode are controlled in this phase. In the second phase, a modified DAC(Discretionary Access Control) model is applied to re-control the 'read' mode by filtering out the non-accessible data from the result obtained at the first phase. For this purpose, we also defined the user group s that can be characterized by security levels, roles or any partition of users. The policies represented in the form of Block(s, d, r) were also defined and used to control access to any data or data group(s) that is not permitted in 'read ' mode. With this proposed security system, more complicated 'read' access to various data sizes for individual users can be flexibly controlled, while other access mode can be controlled as usual. An implementation example for a database system that manages specimen and clinical information is presented.

• Computers and Concrete
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• v.28 no.5
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• pp.441-450
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• 2021

This study presents the first analysis system and fast-access cloud database for shrinkage and creep of concrete in the world, named "shrinkage and creep database in Taiwan", SCDT. SCDT not only has the most comprehensive experimental data, including NU, JSCE, Europe, and TW databases, but provides a design tool for researchers and engineers. It can further facilitate the development of prediction models for localized concrete. Users can obtain the shrinkage and creep curves based on their selected prediction models in SCDT. Comparisons of the predicted results of selected models and test results in the chosen database can be generated in seconds. One example of the development of basic creep prediction model in Taiwan based on model B4 by using SCDT to reflect concrete characteristics in Taiwan is also presented in this study. Users anywhere in the world can easily access SCDT to browse and upload data, receive predictive results, or develop predictive models.

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.103-110
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• 2008

Due to the development of the e-commerce, the shopping mall such as auction collects and manages the personal information of the customers for efficient service. However, because of the leakage of the Personal information in auction, the image of the companies as well as the information subjects is damaged. Even though the organizations and the companies store the personal information as common sentences and protect using role based access control technique, the personal information can be leaked easily in case of getting the authority of the database administrator. And also the role based access control technique is not appropriate for protecting the sensitive information of the information subject. In this paper, we encrypted the sensitive information assigned by the information subject and then stored them into the database. We propose the personal policy based access control technique which controls the access to the information strictly according to the personal policy of the information subject. Through the proposed method we complemented the problems that the role based access control has and also we constructed the database safe from the database administrator. Finally, we get the control authority about the information of the information subject.

• Proceedings of the Korean Society for Language and Information Conference
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• 1995.02a
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• pp.249-254
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• 1995

• Journal of Korean Library and Information Science Society
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• v.25
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• pp.83-107
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• 1996

The purpose of this study is to experiment online public access catalog enhancements to improve its subject access capability. Three catalog databases, enhanced with title keywords, controlled vocabulary, and content words with controlled vocabulary respectively, were implemented. 18 searchers performed 2 subject searshes against 3 different catalog databases. And the transaction logs are analyzed. The results of the study can be summarized as follows : Controlled vocabulary catalog database achieved 41.8% recall ratio in average ; the addition of table of contents words to the controlled vocabulary is an effective technique with increasing recall ration upto 55% without decreasing precision ; and the database enhanced with title keywords shows 31.7% recall ratio in average. Of the three kinds of catalog databases, only the catalog with contents words produced 2 unique relevant documents. The results indicate that both user training and system development is required to have better search performance in online public access catalog.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.10a
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• pp.275-278
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• 1996

We propose dynamic file allocation method in distributed database management system with changing access patterns. There are a lot of studies on file allocation problem in D-DBMS, and those studies deal with off-line analysis and optimization. Those works are well for systems with static database access patterns, but are inadequate for systems that have changing access patterns. In these systems, dynamic file allocation along with access pattern is more proper. In advance, Brunstrom et al. studied on this area, but they dealt a extremely simplified model. So, we make more practical models to simulate real system. In these models, many factors that were disregard in the advance study are considered. These models are composed with the non-replication system and the replication system. In addition to, we deal with CPU workload balancing in such system in order to improve performance of systems. Our methodology is very simple and realistic, therefore we think that it will give a lot of improvement in D-DBMS with changing access pattern.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.4
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• pp.1899-1911
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• 2018

In this work, we propose a concurrency control scheme in object-oriented database (OODB). Since an OODB provides complex modeling power than the conventional relational databases, a concurrency control technique in OODB is also rather complicated and has influence on the overall performance. Thus, it is very important to develop a concurrency control technique with less overhead. The proposed scheme deals with class hierarchy that is a key concept in OODBs. The proposed scheme is developed on implicit locking scheme. Also, the proposed scheme is designed using data access frequency in order to reduce locking overhead than implicit locking. It means that, if access frequency information is not available, the proposed scheme works just like the existing implicit locking, In our work, the correctness of the proposed scheme is proved. The performance is analyzed depending on access types. Also, it is proved that our scheme performs works much better than the implicit locking does.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.149-159
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• 2011

Recently, mobile computing environments are becoming rapidly common. This trend emphasizes the necessity of accessing database systems on fixed networks from mobile platforms via wireless networks. However, it is not an appropriate way that applies the database access methods for traditional computing environments to mobile computing environments because of their essential restrictions. This paper suggests a new agent-based mobile database access model and also two functions calculating data significance scores to choose suitable data items for cache replacement and coherence policies. These functions synthetically reflect access term, access frequency and tendency, update frequency and tendency, and data item size distribution. As the result of simulation experiment, our policies outperform LRU, LIX, and SAIU policies in aspects of decrement of access latency, improvement of cache byte hit ratio, and decrease of cache byte pollution ratio.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.89-97
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• 2009

The use of database system in application increases day by day. This brought out the DBMS interconnection access problem with rapid increase of the user. To solve these database connection problem, database connection pool has been presented. However, there is much to be desired on user's interconnection access. To improve previous connection pool architecture, we have designed the sub connection pool besides main connection pool in this paper. We defined connection pool broker to manage both main and sub connection pool connection. When main connection pool reached its limitation, connection pool broker transfers a connection from a main connection pool to a sub connection pool. When the interconnection access user increased rapidly, we have proved that the suggested sub pool architecture is more effective on response time by comparing it with other existing DBMS connection pool architectures using simulation.

• Journal of Digital Convergence
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• v.11 no.2
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• pp.317-322
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• 2013

Mobile cloud environment is recently becoming popular due to Internet access through various environments. Driven by computer performance improvement and service development, the demand for mobile cloud is increasing and accordingly the damage is on the rise. Therefore, it needs to conduct a study on problems of security necessary in large database that occurs in mobile cloud services. Although various security solutions limiting database access, security strategies about new user environments should be analyzed. This study analyzes weakness of safe data access through database management in mobile cloud environment and examines security requirements for safe data management. In addition, this study looks into threatening factors of security in cloud services and then draws security requirements about safer access control. A study on system application and evaluation of security requirements about access control is required.