Kaname Harumoto

User adaptive content delivery mechanism on the world wide web

To reduce the user-perceived latency in web content delivery, many techniques have been proposed. One is a transmission time control mechanism that automatically adjusts the quality of inline objects, such as images on a web page, according to the client network bandwidth. Another is a transmission order control mechanism that can transmit inline objects in a specified order preferred by users. In this paper, we describe the development of a user adaptive content delivery mechanism that integrates transmission time control and transmission order control. Based on the users preference profile, it dynamically prioritizes inline objects in terms of content quality and delivery order, and provides user with adapted inline objects. A prototype system has been implemented in Java, and gives an example of adapted content delivery.

Effective Web browsing through content delivery adaptation

This article presents a Web content adaptation and delivery mechanism based on application-level quality of service (QoS) policies. To realize effective Web content delivery for users, two kinds of application-level QoS policies, transmission time and transmission order of inline objects, are introduced. Next, we define a language to specify these policies. We show that transmission order control can be implemented using HTTP/1.1 pipelined requests in which a client recognizes the transmission order description in a Web page and simulates parallel transmission of inline objects by HTTP/1.1 range requests. Experimental results show that our proposed mechanism realizes effective content delivery to a diverse group of Internet users. Finally, we introduce two methods to specify application-level QoS policies, one by content authors, and the other by end users.

Dynamic replica allocation using database migration in broadband networks

Dynamic relocation of databases through networks, or database migration, will soon become a powerful standard database operation effectively using recent advances in broadband networks. In our previous work, a transaction processing method has been proposed in distributed database environments, based on database migration operations. Generally, database replication is an effective technique to improve transaction processing throughput in conventional systems. We propose a replica management method for use with database migration. Database migration is used at the beginning of a transaction to dynamically relocate database replicas. The performance of the proposed method is evaluated using simulation results.

Database migration: a new architecture for transaction processing in broadband networks

Due to recent developments in network technologies, broader channel bandwidth is becoming prevalent in worldwide networks. As one of the new technologies making good use of such broadband channels, dynamic relocation of databases through networks, database migration, will soon be used in practice as a powerful and basic database operation. We propose two transaction processing methods to take advantage of database migration in broadband networks. These methods choose the most efficient transaction processing method between the conventional method, based on the two-phase commit protocol, and our method, using database migration. We also propose a concurrency control mechanism and a recovery mechanism for our proposed methods. Simulation results are presented comparing the performance of our proposed methods and the conventional transaction processing method based on the two-phase commit protocol. The results demonstrate that the effective use of database migration produces better performance than the conventional method.

DB-MAN: a distributed database system based on database migration in ATM networks

Because of the recent development of network technologies such as ATM (Asynchronous Transfer Mode), broader channel bandwidth is becoming available everywhere in the world wide networks. As one of the new technologies to make good use of such broadband channel, dynamic relocation of databases through networks, which we call database migration, will soon become a powerful and basic database operation of practical use. We discuss our proposal of a distributed database system, DB-MAN (distributed database system based on DataBase Migration in ATM Networks), which takes advantage of database migration in virtual LANs (local area networks) of ATM networks. DB-MAN has two notable mechanisms: a mechanism for selecting the transaction processing method and a mechanism for concurrency control with database migration. The former, is a mechanism which chooses the more efficient method between two transaction processing methods: the conventional method based on the two phase commit protocol and our method employing database migration. The latter is a mechanism to prevent the transaction processing throughput from deteriorating in environments where data contention is a significant factor. Then we show simulation results regarding performance comparison between our proposed system and the conventional distributed database system based on the two phase commit protocol. The obtained results demonstrate that effective use of database migration gives higher performance than that of the conventional system.

Main memory database for supporting database migration

As one of the new technologies to make good use of broader channel bandwidth of recent networks, dynamic relocation of databases through networks, which we call database migration, will soon become a powerful and basic database operation of practical use. To make full use of database migration, the main memory database is considered to be one of the most significant technologies, because it allows us to perform very high speed database access which almost matches for the transmission rate of broadband networks. In this paper, we first discuss the physical database structure which realizes high speed database migration. Then, we propose the recovery methods for migratory main memory databases.

A sensor data collection method under a system constraint using hierarchical Delaunay overlay network

In this paper, we propose a novel sensor data collection method that forwards messages to the nodes which are suitable for reconstructing of the sensor data distribution by extending hierarchical Delaunay overlay network (HDOV). By our proposal method, contour lines map can be reconstructed according to the requirements, satisfying a specified system constraint of the number of sensor data. The key idea of the method is allocation of the number of sensor data to be collected according to the layered structure of HDOV. The simulation result shows that our proposal can reconstruct contour lines map which focuses on the characteristic point or not, satisfying the specified system constraint.

HDOV: an overlay network for wide area spatial data collection

In this paper, we propose an overlay network called HDOV, a hierarchical extension of Delaunay overlay network for data collection with multiple spatial resolutions. By using HDOV, spatial data with at least specified spatial resolution can be collected reducing the redundant messages for data collection from wide area peer-to-peer network. The proposal in HDOV consists of 1) uniform node selection method for multiple spatial resolution levels and 2) hierarchical overlay network construction methods for the selected nodes. The proposed node selection method in HDOV probabilistically adjusts geographical node densities of the overlay network levels according to the size of the Voronoi cell of each node. We propose two types of hierarchical overlay network construction method: the Selected-Nodes Leading method (SNL) and the Unselected-Nodes Leading method (UNL). Our simulation results show that the proposed method can construct overlay networks that collect data with specified uniform spatial resolutions. The simulation results also show that the UNL requires low network construction cost especially in the skewed node distribution environment and the SNL requires less network reconstruction cost when there are no adjoined node failures.

Realization of personalized presentation for digital contents based on browsing history

Recently, the tremendous amount of information is digitalized and becoming available on the World Wide Web. These digital contents are nowadays easily accessible to a lot of Internet users. However, most web sites today are comprised of a large number of web pages and hyperlinks, often making it difficult for visitors to browse through and to find their desired information quickly. To address the problem, this paper proposes a newly web site personalization method by utilizing content browsing history. Web sites based on our model consist of a set of small components, and browsing history considered as visitors preference is used to identify components to be presented on a web page.

Controlling transmission order of inline objects for effective Web page publishing

Due to the increasing popularity of the Internet, the WWW (World Wide Web) has become the most popular way to distribute multimedia contents. In the WWW, impressive information can be provided by embedding a large number of inline objects such as images in a WWW page. Since these inline objects are generally presented on a WWW browser with the order of transmission, the transmission order of inline objects becomes very important, especially for users accessing the Internet with a low-speed link such as a dial-up line. In this paper, we propose a page transmission mechanism which allows content providers to specify the transmission order of inline objects in WWW pages. First, we define a language to specify the transmission order of inline objects. We then discuss how we can implement the transmission order control, and propose a new protocol, HTSP (Hypertext Streaming Protocol), which realizes efficient transmission of ordered inline objects.