• Journal of KIISE:Databases
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• v.32 no.5
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• pp.487-497
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• 2005

A range mosaic query returns distribution of data within the query region as a pattern of mosaic, whereas a range aggregate query returns a single aggregate value of data within the query region. The range mosaic query divides a query region by a multi-dimensional grid, and calculates aggregate values of grid cells. In this paper, we propose a new type of query, range mosaic query and a new operator, mosaic-by, with which the range mosaic queries can be represented. In addition, we suggest efficient algorithms for processing range mosaic queries using an aggregate R-tree. The algorithm that we present computes aggregate results of every mosaic grid cell by one time traversal of the aggregate R-tree, and efficiently executes the queries with only a small number of node accesses by using the aggregate values of the aggregate R-tree. Our experimental study shows that the range mosaic query algorithm is reliable in terms of performance for several synthetic datasets and a real-world dataset.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.871-885
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• 2015

The improved DFSA for 2.4GHz multi-tags active RFID is suggested in 2 different ways: 1) simplified tag collection and Ack procedure using query command and 2) modified Schoute's method to control the number of slots in the frame. To evaluate the performance of the improved system we develop the simulation model. Varying the number of tags in the system we track the performance measures such as throughput, recognition time for multi-tags and tag recognition rate during a given time. The suggested method shows the best performance over all measures. Simplification of collection and Ack commands using query commands contributes to reducing tag recognition time. And the modified Schoute's method which controls the frame size using $k_1$ and $k_2$ contributes to throughput improvement and reduces target cognition time by reducing the number of collection rounds.

• The KIPS Transactions:PartB
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• v.9B no.1
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• pp.105-112
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• 2002

In order to process video data effectively, we need to save its content on database and a content-based retrieval method which processes various queries of all users is required. In this paper, we present VRS(Video Retrieval System) which provides similarity query, SQBE(Scene Query By Example) query, and content-based retrieval by combining the feature-based retrieval and the annotation-based retrieval. The SQBE query makes it possible for a user to retrieve scones more exactly by inserting and deleting objects based on a retrieved scene. We proposed query language and query processing algorithm for SQBE query, and carried out performance evaluation on similarity retrieval. The proposed system is implemented with Visual C++ and Oracle.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11B
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• pp.685-692
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• 2007

Recent advances in wireless communications and electronics have enabled the development of low-cost, low-power, multi-functional sensors. A typical wireless sensor network (WSN) consists of a large number of sensor nodes that can measure and process data while communicating through wireless channels. In this paper, we propose a hybrid query processing (HQP) algorithm for user queries submitted to the WSN. Unlike previous algorithms that consider continuous queries only, HQP supports both continuous queries and ad-hoc queries. Specially. HQP tries to reduce energy consumption of ad-hoc queries by using query results cached at each sensor node which are created during the execution of the previous continuous query. HQP can also exploit a trade-off between energy consumption and data accuracy. We evaluate the performance of HQP under a variety of WSN configurations.

• Journal of KIISE:Databases
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• v.35 no.6
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• pp.459-468
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• 2008

A data stream which is a massive unbounded sequence of data elements continuously generated at a rapid rate. Many recent research activities for emerging applications often need to deal with the data stream. Such applications can be web click monitoring, sensor data processing, network traffic analysis. telephone records and multi-media data. For this. data processing over a data stream are not performed on the stored data but performed the newly updated data with pre-registered queries, and then return a result immediately or periodically. Recently, many studies are focused on dealing with a data stream more than a stored data set. Especially. there are many researches to optimize continuous queries in order to perform them efficiently. This paper proposes a query optimization algorithm to manage continuous query which has multiple join operators(Multi-way join) over data streams. It is called by an Extended Greedy query optimization based on a greedy algorithm. It defines a join cost by a required operation to compute a join and an operation to process a result and then stores all information for computing join cost and join cost in the statistics catalog. To overcome a weak point of greedy algorithm which has poor performance, the algorithm selects the set of operators with a small lay, instead of operator with the smallest cost. The set is influenced the accuracy and execution time of the algorithm and can be controlled adaptively by two user-defined values. Experiment results illustrate the performance of the EGA algorithm in various stream environments.

• Journal of KIISE:Databases
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• v.29 no.6
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• pp.453-463
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• 2002

With the prevalence of multi-dimensional data such as images, content-based retrieval of data is becoming increasingly important. To handle multi-dimensional data, multi-dimensional index structures such as the R-tree, Rr-tree, TV-tree, and MVP-tree have been proposed. Numerous research results on how to effectively manipulate these structures have been presented during the last decade. Query processing strategies, which is important for reducing the processing time, is one such area of research. In this paper, we propose query processing algorithms for R-tree based structures. The novel aspect of these algorithms is that they make use of the notion of VP filtering, a concept borrowed from the MVP-tree. The filtering notion allows for delaying of computational overhead until absolutely necessary. By so doing, we attain considerable performance benefits while paying insignificant overhead during the construction of the index structure. We implemented our algorithms and carried out experiments to demonstrate the capability and usefulness of our method. Both for range query and incremental query, for all dimensional index trees, the response time using VP filtering was always shorter than without VP filtering. We quantitatively showed that VP filtering is closely related with the response time of the query.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.307-312
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• 2007

Wireless Sensor Network(WSN) is considered as a core technology necessary for Ubiquitous computing, with its numerous possible applications in many practical areas, is being researched and studied actively by many around the world. WSN utilizes wireless sensors spatially placed to gather information regarding temperature, light condition, motion and change in speed of the objects within their surrounding environment. This paper implements an environmental information monitoring and indexing system based on spatial indexing technique by constructing a WSN system. This Multi-Query Indexing Technique coupled with wireless sensors provides an output based on the pre-defined built-in data index and new input from the sensors. If environment data is occured, system have to perform a proper action after collecting and analyzing this data. This is the purpose of implementing environment data monitoring system. We constructed environmental application using TinyOS and built tested with MICAz sensor bords. We designed and implemented a monitoring system which detects and multi-indexing process environmental data from distributed sensors.

• The KIPS Transactions:PartD
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• v.12D no.4 s.100
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• pp.531-542
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• 2005

In this paper, we propose the MDBMS(Multi-DataBase Management System) which integrates the LDBMSs(Local DataBase Systems) with heterogeneous environment into distributed system and provides global users with rapidly query process. For designing the MDBMS, we define the functions of components and design the interaction among them. In a point of view of the global view manager in components, we describe the following 3 cases; (1)the case which the results for the global query are all stored to the global view repository, (2)the case which no result exists in the global view repository, and (3)the case which the partial results we stored to the global view repository. By comparing above cases, we establish the functionalities of our MDBMS through the sequence diagram including the interlace of among objects and the method calling. Finally, we propose the model designed in the concrete by showing the executing procedures of each function using sample query on established functions mentioned above.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.99-108
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• 2010

RFID(Radio Frequency IDentification) is a technology that automatically identifies objects containing the electronic tags by using radio wave. When there are some tags in the domain of the RFID reader, the mechanism that can solve a collision between the tags occurs is necessary. The multi tag identification problem is the core issue in the RFID and could be resolved by the anti-collision algorithm. However, RFID system has another problem. The problem id user information security. Tag response easily by query of reader, so the system happened user privacy violent problem by tag information exposure. In the case, RFID system id weak from sniffing by outside. In this paper, We study of security robustness for tree-walking algorithm, query tree algorithm and advanced query tree algorithm of tree based memoryless algorithm.

• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.2
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• pp.131-156
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• 1998

Cooperative query answering is a research effort to develop a fault-tolerant and intelligent database system using the semantic knowledge base constructed from the underlying database. Such knowledge base has two aspects of usage. One is supporting the cooperative query answering Process for providing both an exact answer and neighborhood information relevant to a query. The other is supporting ongoing maintenance of the knowledge base for accommodating the changes in the knowledge content and database usage purpose. Existing studies have mostly focused on the cooperative query answering process but paid little attention on the dynamic knowledge base maintenance. This paper proposes a multi-level knowledge representation framework called Knowledge Abstraction Hierarchy (KAH) that can not only support cooperative query answering but also permit dynamic knowledge maintenance. The KAH consists of two types of knowledge abstraction hierarchies. The value abstraction hierarchy is constructed by abstract values that are hierarchically derived from specific data values in the underlying database on the basis of generalization and specialization relationships. The domain abstraction hierarchy is built on the various domains of the data values and incorporates the classification relationship between super-domains and sub-domains. On the basis of the KAH, a knowledge abstraction database is constructed on the relational data model and accommodates diverse knowledge maintenance needs and flexibly facilitates cooperative query answering. In terms of the knowledge maintenance, database operations are discussed for the cases where either the internal contents for a given KAH change or the structures of the KAH itself change. In terms of cooperative query answering, database operations are discussed for both the generalization and specialization Processes, and the conceptual query handling. A prototype system has been implemented at KAIST that demonstrates the usefulness of KAH in ordinary database application systems.