• Journal of KIISE:Databases
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• v.35 no.6
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• pp.518-532
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• 2008

Broadcast scheme has been widely researched for efficient data delivery in the mobile environment because the downlink capacity of a mobile client is much greater than the uplink capacity, and the power of a mobile client is limited. In the proposed scheme, the index lets the client know when data items would be broadcasted and enables the client to minimize the tuning time and power consumption. Single channel index schemes are fit to flat broadcast that performs well when all the broadcasted data items are accessed with the same probability whereas the multi-disk broadcast scheme is proper when the data access distribution is skewed. The existing index schemes, however, cannot work on the Multi-disk broadcast scheme because they cannot point the replicating data items in a broadcast cycle. This paper proposes a Multi-disk Exponential Index (MDEI) which is a single channel index scheme fit to Multi-disk broadcast scheme. Because MDEI scheme organizes a separate index for each disk, it functions with multi-disk broadcast, resulting in a greater reduction of average access latency than that of other flat-broadcast index schemes when the data access distribution is skewed. The performance evaluation showed that MDEI has a good performance when data access distribution is skewed. MDEI has short average access latency and not much average tuning time when the data access distribution is skewed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.293-300
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• 2016

Traditional databases exploit a record-based model, where the attributes of a record are placed contiguously in a slow hard disk to achieve high performance. On the other hand, for read-intensive data analysis systems, the column-based compressed database has become a proper model because of its superior read performance. Currently, flash memory SSD is largely recognized as the preferred storage media for high-speed analysis systems. This paper introduces a compressed column-storage model and proposes a new index and its data management scheme for a high-capacity data warehouse system. The proposed index management scheme is based on the asymmetric index duplication and achieves superior search performance using the master index and compact index, particularly for large read-mostly databases. In addition, the data management scheme contributes to the read performance and high reliability by compressing the related columns and replicating them in two mirrored SSD. Based on the results of the performance evaluation under the high workload conditions, the data management scheme outperforms the traditional scheme in terms of the search throughput and response time.

• Journal of Korea Multimedia Society
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• v.9 no.3
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• pp.265-278
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• 2006

This paper presents a two-dimensional type inheritance hierarchy index(2D-THI) for XML databases. XML Schema is one of schema models for the XML documents supporting. The type inheritance. The conventional indexing techniques for XML databases can not support XML queries on type inheritance hierarchies. We construct a two-dimensional index structure using multidimensional file organizations for supporting type inheritance hierarchy in XML queries. This indexing technique deals with the problem of clustering index entries in the two-dimensional domain space that consists of a key element domain and a type identifier domain based on the user query pattern. This index enhances query performance by adjusting the degree of clustering between the two domains. For performance evaluation, we have compared our proposed 2D-THI with the conventional class hierarchy indexing techniques in object-oriented databases such as CH-index and CG-tree through the cost model. As the result of the performance evaluations, we have verified that our proposed two-dimensional type inheritance indexing technique can efficiently support the query Processing in XML databases according to the query types.

• The Journal of the Korea Contents Association
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• v.15 no.1
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• pp.9-23
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• 2015

In this paper, we propose a new RDF index scheme considering the characteristics of large scale RDF data to improve the query processing performance. The proposed index scheme creates a S-O index for subjects and objects since the subjects and objects of RDF triples are used redundantly. In order to reduce the total size of the index, it constructs a P index for the relatively small number of predicates in RDF triples separately. If a query contains the predicate, we first searches the P index since its size is relatively smaller compared to the S-O index. Otherwise, we first searches the S-O index. It is shown through performance evaluation that the proposed scheme outperforms the existing scheme in terms of the query processing time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.166-174
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• 2010

SSDs are one of the best media to support portable and desktop computers' storage devices. Their features include non-volatility, low power consumption, and fast access time for read operations, which are sufficient to present flash memories as major database storage components for desktop and server computers. However, we need to improve traditional index management schemes based on B-Tree due to the relatively slow characteristics of flash memory operations, as compared to RAM memory. In order to achieve this goal, we propose a new index management scheme based on a compressed hot-cold clustering called CHC-Tree. CHC-Tree-based index management improves index operation performance by dividing index nodes into hot or cold segments and compressing pointers and keys in the index nodes and clustering the hot or cold segments. The offset compression techniques using unused free area in cold index node lead to reduce the number of slow erase operations in index node insert/delete processes. Simulation results show that our scheme significantly reduces the write and erase operation overheads, improving the index search performance of B-Tree by up to 26 percent, and the index update performance by up to 23 percent.

• Journal of Korea Spatial Information System Society
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• v.9 no.1
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• pp.31-43
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• 2007

Sensor data have the characteristics such as numerous and continuous data. Therefore, it is required to develop an index which could retrieve a specific sensor data efficiently from numerous sensed data. The index should have an efficient delete operation for the past data to support the data archiving. In this paper, we have proposed and implemented an index splitting technique to support the sensor data archiving. These splitted indexes compose of a virtual index (that is, index management component), which is shown as single tree from outside. Experimental results show that in the case of 100,000 insert operations the splitted index performs 8% better than the traditional TB-tree maximumly. And the splitted index outperforms TB-tree with retrieving queries when the region of query is small and the size of time domain is large.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.1
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• pp.12-23
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• 2001

Extended path expressions are used to denote multiple paths concisely by using '$\ast$' character. They are convenient for expressing OQL queries to retrieve XML data stored in OODBs. In this paper, we propose a multi-path index scheme as a new index scheme to efficiently process queries with extended path expressions. Our proposed index scheme allocates a unique path identifier for every possible single path in an extended path expression and provides functionalities of both a single path indexing and multiple path indexing through the composition of index key and path identifier while using only a index structure. The proposed index scheme provides better performance than single-path index schemes, and is practical since it can be implemented by little modification of leaf records of a B+-tree index.

• The KIPS Transactions:PartB
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• v.15B no.4
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• pp.355-364
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• 2008

In general, we can use an inverted index for retrieving element lists from structured documents. An inverted index can retrieve a list of elements that have the same tag name. In this approach, however, the cost of query processing is linear to the length of a path query because all the structural relationships (parent-child and ancestor-descendant) should be resolved by structural join operations. In this paper, we propose an inverted index technique and a novel structural join technique for accelerating XML path query evaluation. Our inverted index can retrieve element lists for path segments in a parent-child relationship. Our structural join technique can handle lists of element pairs while the existing techniques handle lists of elements. We show through experiments that these two proposed techniques are integrated to accelerate evaluation of XML path queries.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.43 no.1 s.307
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• pp.35-44
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• 2006

Recently, a lot of index techniques for storing and querying XML document have been studied so far and many researches of them used coordinate-based methods. But update operation and query processing to express structural relations among elements, attributes and texts make a large burden. In this paper, we propose an efficient BitmapInvert index technique based on Relative Position Coordinate (RPC). RPC has good preformance even if there are frequent update operations because it represents relationship among parent node and left, right sibling nodes. BitmapInvert index supports tort query with bitwise operations and does not casue serious performance degradations on update operations using PostUpdate algerian. Overall, the performance could be improved by reduction of the number of times for traversing nodes.

• Journal of Korea Multimedia Society
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• v.8 no.2
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• pp.154-163
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• 2005

Because most researches that were studied so far on XML documents used an absolute coordinate system in most of the index techniques, the update operation makes a large burden. To express the structural relations between elements, attributes and text, we need to reconstruct the structure of the coordinates. As the reconstruction process proceeds through out the entire XML document in a cascade manner, which is not limited to the current changing node, a serious performance problem may be caused by the frequent update operations. In this paper, we propose an index technique based on extensible index that does not cause serious performance degradations. It can limit the number of node to participate in reconstruction process and improve lots of performance capacities on the whole. And extensible index performs the containment relationship query by the simple expression using SQL statement.