• The KIPS Transactions:PartD
• /
• v.8D no.6
• /
• pp.813-822
• /
• 2001

In this paper we proposed four data migration methods based on time segmented storage structure including past segment, current segment, and future segment. The migration methods proposed in this paper are the Time Granularity migration method, the LST-GET (Least valid Start Time-Greatest valid End Time) migration method, the AST-AET (Average valid Start Time-Average valid End Time) migration method, and the Min-Overlap migration method. In the each data migration method we define the dividing criterion among segments and entity versions to store on each segment. We measured the response time of queries for the proposed migration methods. When there are no LLTs (Long Lived Tuples), the average response time of AST-AET migration method and LST-GET migration method are smaller than that of Time Granularity migration method. In case of existing LLT, the performance of the LST-GET migration method decreased. The AST-AET migration method resulted in better performance for queries than the Time Granularity migration method and the LST-GET migration method. The Min-Overlap migration method resulted in the almost equal performance for queries compared with the AST-AET migration method, in case of storage utilization more efficient than the AST-AET.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.4
• /
• pp.865-870
• /
• 2005

The latest Global Positioning System, wireless communications technology and Location-Based Service bring about the rapid developments of telematics application areas. In the moving object database for telematics, it is very important to deal with database queries related to the real time current positions of a moving objects and the valid tine of the query results as well. In this paper, we propose how to get not only the current result of query but also the valid time and the result after the valid time when a query point and objects are moving simultaneously. We would like to predict the valid time by formula because the current results will be incorrect due to the characteristic of the continuous movements of the moving objects and the future results can not be calculated by iterative computations.

• Journal of KIISE:Databases
• /
• v.28 no.3
• /
• pp.384-394
• /
• 2001

In this paper, we propose AST-AET(Average valid Start Time-Average valid End Time) data migration strategy based on the storage structure where temporal data is divided into a past segment, a current segment, and a future segment. We define AST and AET which are used in AST-AET data migration strategy and also define entity versions to be stored in each segment. We describe methods to compute AST and AET, and processes to search entity versions for migration and move them. We compare average response times for user queries between AST-AET data migration strategy and the existing LST-GET(Least valid Start Time-Greatest valid End Time) data migration strategy. The experimental results show that, when there are no LLTs(Long Lived Tuples), there is little difference in performance between the two migration strategies because the size of a current segment is nearly equal. However, when there are LLTs, the average response time of AST-AET data migration strategy is smaller than that of LST-GET data migration strategy because the size of a current segment of LST-GET data migration strategy becomes larger. In addition, when we change average interarrival times of temporal queries, generally the average response time of AST-AET data migration strategy is smaller than that of LST-GET data migration strategy.

• Journal of Information Processing Systems
• /
• v.2 no.1
• /
• pp.1-5
• /
• 2006

Finding a valid timing constraint is one of the most important issues in the real-time monitoring area. To get the valid timing constraint, a developer executes a real-time process and changes the constraint on a regular basis. This is an exhaustive and time-consuming process. To improve this approach, we propose a timing constraint search technique. This technique uses two load models and one condition proposed in this paper to support the developer in determining the valid timing constraint range in an easy and systematic manner.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.12
• /
• pp.2947-2959
• /
• 1997

Temporal data model is able to handle the time varying information, which is to add temporal attributes to conventional data model. The temporal data model is classified into three models depending upon supporting time dimension, that are the valid time model to support valid time, the transaction time model to support transaction model, and the bitemporal data model to support valid time and transaction time. Most temporal data models are designed to process the temporal data by extending the relational model. There are two types or temporal data model, which are the tuple timestamping and the attribute timestamping depending on time dimension. In this research, a concepts of temporal data model, the time dimension, types of thc data model, and a consideration for the data model design are discussed Also, temporal data models in terms of the time dimension are compared. And the aggregate function model of valid time model is proposed, and then logical analysis for its computing consts has been done.

• Journal of Korea Multimedia Society
• /
• v.21 no.2
• /
• pp.232-241
• /
• 2018

Operational Transformation (OT) algorithms for real-time collaborative editing systems are becoming increasingly important due to the increased demand for collaborative data processing. The operational transformation algorithm is a technique for real-time concurrency control and consistency maintenance with non-locking technique, and many studies have been conducted to overcome three issues of convergence, causality-prevention, and intention-prevention. However, previous work has the disadvantage of wasting memory by storing all operations that occurred during an edit operation in the history buffer to solve this problem. Therefore, we propose a memory-saving real-time collaborative editing system that maintains a constant memory space and concurrency control through a method of applying the valid-time to each user-generated operation in order to reduce memory waste. This system prevents long-term memory occupation of client-generated operations, thus it reduces the space and time complexity even with low-rate of collaboration work, so that the performance degradation avoids.

• Journal of KIISE:Information Networking
• /
• v.30 no.4
• /
• pp.484-493
• /
• 2003

Proxy signature scheme is a cryptographic protocol that an original signer delegates her signing capability to a proxy signer, and then the proxy signer is able to create signatures on behalf of the original signer. In general, there is time-limit for which the signing capability of the proxy signer is valid. One of methods to limit the valid delegation time is to make public delegation information contain the expiration date of the delegation. however, in this method we cannot prevent the proxy signer from signing after the valid delegation is expired because no one knows the exact time when the proxy signer signed a message. The validity of the past legal signatures cannot be preserved in case that the proxy singer´s key is compromised during the delegation period. In this paper, we propose a new scheme, time-limited forward-secure proxy signature protocol, which prevents the proxy singer from signing after the valid delegation is expired and which preserves the validity of the past legal signatures even if the signing key is compromised. The proposed scheme does not require the exact time-information by making an original signer control time-related parameters and satisfies the forward-security property in each update-period of the proxy signing key. The time-period is determined according to the application characteristics or security policies.

• ETRI Journal
• /
• v.30 no.1
• /
• pp.167-169
• /
• 2008

In this paper, we propose hardware architecture for a high-speed context-adaptive variable length coding (CAVLC) decoder in H.264. In the CAVLC decoder, the codeword length of the current decoding block is used to determine the next input bitstreams (valid bits). Since the computation of valid bits increases the total processing time of CAVLC, we propose two techniques to reduce processing time: one is to reduce the number of decoding steps by introducing a lookup table, and the other is to reduce cycles for calculating the valid bits. The proposed CAVLC decoder can decode $1920{\times}1088$ 30 fps video in real time at a 30.8 MHz clock.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.1
• /
• pp.91-98
• /
• 2023

With the increasing flood damage by frequently localized heavy rains, flood prediction research are being conducted to prevent flooding damage in advance. In this paper, we present a machine-learning scheme for developing a flooding depth and location prediction model using real-time rainfall data. This scheme proposes a dataset configuration method using the data as input, which can robustly configure various rainfall distribution patterns and train the model with less memory. These data are composed of two: valid total data and valid local. The one data that has a significant effect on flooding predicted the flooding location well but tended to have different values for predicting specific rainfall patterns. The other data that means the flood area partially affects flooding refers to valid local data. The valid local data was well learned for the fixed point method, but the flooding location was not accurately indicated for the arbitrary point method. Through this study, it is expected that a lot of damage can be prevented by predicting the depth and location of flooding in a real-time manner.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.1
• /
• pp.163-166
• /
• 2005

The latest wireless communications technology bring about the rapid developments of Global Position System and Location-Based Service. It is very important for the moving object database to deal with database queries related to the trajectories of a moving objects and the valid time of the query results as well. In this paper, we propose how to get not only the current result of query but also the valid time and the result after the time when a query point and objects are moving at the same time. We would like to predict the valid time by formula because the current results will be incorrect due to the characteristic of the continuous movements of the moving objects and the future results can not be calculated by iterative computations.