• Review of KIISC
• /
• v.6 no.1
• /
• pp.45-56
• /
• 1996

본 논문의 목적은 객체지향 데이타베이스(object-oriented database : OODB)의 보안성 확보를 위하여 OODB에 관련된 보안 모델과, 질의 처리시에 보안성 확보를 위한 참조제약 규칙을 제안하는 것이다. 본 논문의 철학은 데이타베이스 모델의 제약사항을 최소화여 융통성을 최대한으로 확보하고, 이들의 보안성 보장은 질의 처리시에 담당하게 함으로서 풍부한 데이타 객체 모델을 가질 수 있을 뿐만 아니라 낙관적인 보안성 확보를 통하여 융통성 있는 질의처리를 도모하였다. 이를 위하여 현실세계의 모든 개체의 특징과 행위를 구체적으로 표현한 추상화 단위로 정의되는 객체를 기밀성에 따라 비밀등급으로 보안 분류하여 보관된 다단계 보안 객체의 모델을 기반으로 한다. 대부분 기존의 보안성 연구의 대상은 수동적인 데이타(passive data)이라면 객체지향 데이터베이스는 능동적인 객체(active object)가 보안성 연구의 대상이 된다.

• Journal of Korean Society for Geospatial Information Science
• /
• v.3 no.1 s.5
• /
• pp.45-54
• /
• 1995

The relational data model is based on mathematical concept of relations and is well formulated, and so there have been numerous practical applications and studies. However, it is not suitable for representing a complex hierarchical structure, which is the characteristic of most geographical objects. On the other hand, the object-oriented data model can naturally represent a complex hierarchical structure, but there is a difficulty in sharing data with the relational data model which is currently used by most commercial GIS users. Also it has no standard query language with standardized format. In this paper, we propose an Object Grouping based on RDBMS to use data from a traditional relational data model while supporting various concepts of the object-oriented data model, and we applied this data model to design a GIS.

• Spatial Information Research
• /
• v.3 no.2
• /
• pp.191-204
• /
• 1995

The data model is a system model which abstracts the spatial and nonspatial fea¬tures of the real world. A system defines through its data model a framework for the inner rep¬resentation of and connections with the outside world. The spatial query language is one of the most efficent framework for defining connection with outside world in the GIS. Existing GIS uses a spatial data model based on relational data model. Therefore, it has some difficulties in data abstraction and representing complex objects through inheritance. In this paper, we pro-pose an object oriented data model-Topological Object Model(TOM). TOM combines object model in ODMG and the planer topological object. Based on this model, we present an object-oriented spatial query language-OQL/Geo. OQL/Geo extends OQL in ODMG and represents TOM effectively. It also provides several operators such as geometric, topological and visible ope-rators. Moreover, it represents with diverse flexivility the request for complex spatial analysis and presentation of query results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.3
• /
• pp.277-287
• /
• 1992

In this paper, we study the performance eualuations of the FDDI Network, by mathmeticlal analysis and simulation, in which the Integrated Voice/Data transmission system with voice traffic in synchronous mode and data traffic inasynchronous mode.For the mean waiting times of Voice/Data packet, we use two-state of Marcov models for voice traffic with talkspurt and silenci state, and the data traffic would traffic would transmit at the silence state of voice traffic. By the mean wating times, we analyze the relations between synchronous and asynchronous mode. As a result, using Sync/Async mode with voice and data, voice was not under influnece of data traffic. and in the same time,data can be tanaxmitted in a short waiting time, too.

• Journal of KIISE:Databases
• /
• v.34 no.6
• /
• pp.483-492
• /
• 2007

Time series of conventional prediction techniques uses the model which is generated from the training step. This model is applied to new input data without any change. If this model is applied directly to stream data, the rate of prediction accuracy will be decreased. This paper proposes an stream data prediction technique using sliding window and regression. This technique considers the characteristic of time series which may be changed over time. It is composed of two steps. The first step executes a fractional process for applying input data to the regression model. The second step updates the model by using its information as new data. Additionally, the model is maintained by only recent data in a queue. This approach has the following two advantages. It maintains the minimum information of the model by using a matrix, so space complexity is reduced. Moreover, it prevents the increment of error rate by updating the model over time. Accuracy rate of the proposed method is measured by RME(Relative Mean Error) and RMSE(Root Mean Square Error). The results of stream data prediction experiment are performed by the proposed technique IMQR(Incremental Multiple Quadratic Regression) is more efficient than those of MLR(Multiple Linear Regression) and SVR(Support Vector Regression).

• Journal of KIISE:Databases
• /
• v.27 no.2
• /
• pp.227-237
• /
• 2000

A Web database System is a large-scaled multimedia application system that has multimedia processing facilities and cooperates with relational/Object-Oriented DBMS. Conventional hypertext modeling methods and DB gateway have limitations for Web database because of their restricted versatile presentation abilities and inefficient concurrency control caused by bottleneck in cooperation processing. Thus, we suggest a Dynamic Navigation Model & Virtual Graph Structure. The Dynamic Navigation Model supports implicit query processing and dynamic creation of navigation spaces, and introduce node-link creation rule considering navigation styles. We propose a mapping methodology between the suggested hypertext model and the relational data model, and suggest a dynamic allocation scheduling technique for query processing server based on weighted value. We show that the proposed technique enhances the retrieval performance of Web database systems in processing complex queries concurrently.

• The Journal of Natural Sciences
• /
• v.8 no.1
• /
• pp.115-121
• /
• 1995

The Conventional database management system is not applicable because of their inadequate performance and difficulty of CAD database that is dependant to hierarchical structure and to repeat accesses of large data. For effective management and easy tool integration of CAD database, hierarchy Interface System(HIS) is designed and GROCO(Graph Representation fOr Complex Objects) Model is presented. Hierarchy Interface System which is composed of two subsystems of a configurator and a converter is designed for the interface between a conventional database management system and CAD tools. GROCO Model is a directed cyclic graph having five node-types for representing semantics and supports efficiently CAD database characters having a hierarchical structure of complex objects.

• Journal of KIISE:Databases
• /
• v.32 no.5
• /
• pp.473-486
• /
• 2005

The Hippocratic database model recently proposed by Agrawal et at. incorporates privacy protection capabilities into relational databases. The authors have subsequenty proposed the Hippocratic XML daかabase model[4], an extension of the Hippocratic database model for XML databases. In this paper, we propose a new concept that we cail the dynamic predicate(DP) for effective access control in the Hippocratic XML database model. A DP is a novel concept that represents a dynamically constructed rendition that tan be adapted for determining the accessibility of elements during query execution. DPs allow us to effectively integrate authorization checking into the query plan so that unauthorized elements are excluded in the process of query execution. Using synthetic and real data, we have performed extensive experiments comparing query processing time with those of existing access control mechanisms. The results show that the proposed access control mechanism improves the wall clock time by up to 219 times over the top-down access control strategy and by up to 499 times over the bottom-up access control strategy. The major contribution of our, paper is enabling effective integration of access control mechanisms with the query plan using the DP under the Hippocratic XML database model.

• Journal of KIISE:Databases
• /
• v.30 no.5
• /
• pp.494-506
• /
• 2003

Recently, explosive popularity of multimedia information has triggered the need for retrieving multimedia contents efficiently from the database including audio, video and images. In this paper, we propose an XML-based retrieval scheme and a data model that complement the weak aspects of annotation and conent based retrieval methods. The Property and hierarchy structure of image and video data are represented and manipulated based on the Multimedia Description Schema (MDS) that conforms to the MPEG-7 standard. For audio contents, pitch contours extracted from their acoustic features are converted into UDR string. Especially, to improve the retrieval performance, user's access pattern and frequency are utilized in the construction of an index. We have implemented a prototype system and evaluated its performance through various experiments.

• Journal of KIISE:Computer Systems and Theory
• /
• v.33 no.9
• /
• pp.563-573
• /
• 2006

Cyber-infrastructures for scientific and engineering applications require integrating heterogeneous legacy data in different formats and from various domains. Such data integration raises challenging issues: (1) Support for multiple independently-managed schemas, (2) Ease of schema evolution, and (3) Simple schema mappings. In order to address these issues, we propose a novel approach to semantic integration of scientific data which uses XML schemas and RDF-based schema mappings. In this approach, XML schema al-lows scientists to manage data models intuitively and to use commodity XML DBMS tools. A simple RDF-based ontological representation scheme is used for only structural relations among independently-managed XML schemas from different institutes or domains We present the design and implementation of a prototype system developed for the national cyber-environments for civil engi-neering research activities in Korea (similar to the NEES project in USA) which is called KOCEDgrid (http://www.koced.net).